Mark Pezzano | The City College of New York (original) (raw)

Papers by Mark Pezzano

Research paper thumbnail of Dkk1 mediated inhibition of Wnt Signaling in postnatal mice leads to loss of TEC progenitors and thymic degeneration (36.32)

Journal of Immunology, Apr 1, 2010

Background: Thymic epithelial cell (TEC) microenvironments are essential for the recruitment of T... more Background: Thymic epithelial cell (TEC) microenvironments are essential for the recruitment of T cell precursors from the bone marrow, as well as the subsequent expansion and selection of thymocytes resulting in a mature self-tolerant T cell repertoire. The molecular mechanisms, which control both the initial development and subsequent maintenance of these critical microenvironments, are poorly defined. Wnt signaling has been shown to be important to the development of several epithelial tissues and organs. Regulation of Wnt signaling has also been shown to impact both early thymocyte and thymic epithelial development. However, early blocks in thymic organogenesis or death of the mice have prevented analysis of a role of canonical Wnt signaling in the maintenance of TECs in the postnatal thymus. Methodology/Principal Findings: Here we demonstrate that tetracycline-regulated expression of the canonical Wnt inhibitor DKK1 in TECs localized in both the cortex and medulla of adult mice, results in rapid thymic degeneration characterized by a loss of DNP63 + Foxn1 + and Aire + TECs, loss of K5K8DP TECs thought to represent or contain an immature TEC progenitor, decreased TEC proliferation and the development of cystic structures, similar to an aged thymus. Removal of DKK1 from DKK1-involuted mice results in full recovery, suggesting that canonical Wnt signaling is required for the differentiation or proliferation of TEC populations needed for maintenance of properly organized adult thymic epithelial microenvironments. Conclusions/Significance: Taken together, the results of this study demonstrate that canonical Wnt signaling within TECs is required for the maintenance of epithelial microenvironments in the postnatal thymus, possibly through effects on TEC progenitor/stem cell populations. Downstream targets of Wnt signaling, which are responsible for maintenance of these TEC progenitors may provide useful targets for therapies aimed at counteracting age associated thymic involution or the premature thymic degeneration associated with cancer therapy and bone marrow transplants.

Research paper thumbnail of The Research Centers in Minority Institutions (RCMI) Translational Research Network: Building and Sustaining Capacity for Multi-Site Basic Biomedical, Clinical and Behavioral Research

Ethnicity & Disease, Feb 21, 2019

Services (DHHS) action plan to reduce racial and ethnic health disparities emphasizes the importa... more Services (DHHS) action plan to reduce racial and ethnic health disparities emphasizes the importance of a diverse workforce. 1 A growing field of investigation has unveiled the

Research paper thumbnail of Bone marrow-derived cells contribute to the maintenance of thymic stroma including thymic epithelial cells

Journal of Immunology, May 1, 2020

Research paper thumbnail of Wnt signaling during thymic involution and reconstitution. (HEM7P.226)

The Journal of Immunology

Despite its critical role in T-cell development, the thymus undergoes profound age-related involu... more Despite its critical role in T-cell development, the thymus undergoes profound age-related involution. Inhibition of Wnt signaling in thymic epithelium (TECs) leads to rapid involution. Lack of a Wnt reporter that was functional in TECs hindered characterization of Wnt signaling during TEC ontogeny. Using the TCF/LEF-H2BGFP Wnt reporter mouse, TECs undergoing active Wnt signaling were characterized during different stages of thymic aging and recovery. In the postnatal thymus, H2BGFP expression was restricted to TECs in the medulla and CMJ including 60% of the Aire-expressing mTECs, suggesting a role for Wnt signaling in the development of this critical TEC subset. Comparison of the TECs undergoing Wnt signaling in old versus young thymus revealed an increase in the frequency of TECs undergoing Wnt signaling even though overall TEC numbers decreased significantly with age. The decrease in both total TECs and TECs undergoing Wnt signaling was most apparent in the UEA1hi mTEC subset an...

Research paper thumbnail of Decision letter: Fine-tuning of β-catenin in mouse thymic epithelial cells is required for postnatal T-cell development

Research paper thumbnail of Content Alerts

This article cites 57 articles, 11 of which can be accessed free at:

Research paper thumbnail of Thymic Nurse Cell Multicellular Complexes in HY-TCR Transgenic Mice Demonstrate Their Association with MHC Restriction

Experimental Biology and Medicine, 2007

This study examines thymic nurse cell (TNC) function during T-cell development. It has been sugge... more This study examines thymic nurse cell (TNC) function during T-cell development. It has been suggested that TNCs function in the removal of nonfunctional and/or apoptotic thymocytes and do not participate in major histocompatibility complex restriction. We analyzed TNCs isolated from both normal C57BL/6 mice and C57BL/6 TgN (TCRHY) mice (HY-TCR transgenic mice). Using confocal microscopic analyses of TNCs isolated from C57BL/6 animals, we showed that 75%–78% of the enclosed thymocyte subset was viable, and 87%–90% of these cells expressed both CD4 and CD8. CD4 and CD8 also were expressed on TNC thymocytes isolated from both male and female HY-TCR transgenic mice. The transgenic female thymus was shown to have 17 times more TNCs per milligram of thymus than the transgenic male thymus. TNCs from HY-TCR transgenic females were 8–10 μm larger than transgenic male TNCs, and the female TNCs contained five times more thymocytes within intracytoplasmic vacuoles, with less than 4% apoptosis. ...

Research paper thumbnail of The Wnt Signaling Antagonist Kremen1 is Required for Development of Thymic Architecture

Clinical and Developmental Immunology, 2006

Wnt signaling has been reported to regulate thymocyte proliferation and selection at several stag... more Wnt signaling has been reported to regulate thymocyte proliferation and selection at several stages during T cell ontogeny, as well as the expression ofFoxN1in thymic epithelial cells (TECs). Kremen1 (Krm1) is a negative regulator of the canonical Wnt signaling pathway, and functions together with the secreted Wnt inhibitor Dickkopf (Dkk) by competing for the lipoprotein receptor-related protein (LRP)-6 co-receptor for Wnts. Herekrm1knockout mice were used to examinekrm1expression in the thymus and its function in thymocyte and TEC development.krm1expression was detected in both cortical and medullary TEC subsets, as well as in immature thymocyte subsets, beginning at the CD25+CD44+ (DN2) stage and continuing until the CD4+CD8+(DP) stage. Neonatal mice show elevated expression ofkrm1in all TEC subsets.krm1− / −mice exhibit a severe defect in thymic cortical architecture, including large epithelial free regions. Much of the epithelial component remains at an immature Keratin 5+(K5) K...

Research paper thumbnail of Circulating Macrophages as Well as Developing Thymocytes Are Enclosed within Thymic Nurse Cells

Cellular Immunology, 2001

Both thymic nurse cells (TNCs) and macrophages have been reported to function as antigen-presenti... more Both thymic nurse cells (TNCs) and macrophages have been reported to function as antigen-presenting cells during the process of MHC restriction. Negative selection, which results in the apoptosis of potentially autoreactive thymocytes, is believed to be associated with both macrophages and TNCs in the cortex. Both cell types have also been reported to ingest thymocytes undergoing positive and negative selection. However, macrophages ingest apoptotic thymocytes, while TNCs have been shown to internalize viable cells. A subset of the TNC-engulfed population is allowed to mature and is released, while the remaining fraction becomes apoptotic and is absorbed within the TNC cytoplasm through lysosomal activity. A recent report described a subset of rat TNCs that contain macrophages as well as thymocytes within their cytoplasm. We examined freshly isolated TNCs from C57BL/6 mice and found that, of the TNC population recovered, 1.7% contained macrophages within its cytoplasm. There also were macrophages tightly bound but not internalized into the multicellular structure at a rate of 2.9%. The total association of macrophages with TNCs was approximately 4.6%. This unique association of macrophages with TNCs was also observed in vitro when freshly isolated thymocytes (containing macrophages) were added to cultures of cells from the TNC cell line tsTNC-1. The macrophage-TNC interaction was found to be dynamic, with macrophages moving rapidly into and out of TNCs containing cytoplasmic thymocytes. Macrophages within TNCs showed a close association with cytoplasmic thymocytes. We then labeled peritoneal macrophages with CFDA SE, a cell tracking dye, and returned them to the mouse peritoneum. Within 1 h, labeled macrophages were detectable in the thymus. This is the first investigation to show a direct interaction between peripheral macrophages and TNCs. These results suggest that TNCs and macrophages work together as antigen-presenting cells.

Research paper thumbnail of Thymic nurse cells exclusively bind and internalize CD4+CD8+ thymocytes

Cellular Immunology, 1992

Thymic nurse cells (TNC) contain 20-200 thymocytes within specialized vacuoles in their cytoplasm... more Thymic nurse cells (TNC) contain 20-200 thymocytes within specialized vacuoles in their cytoplasm. The purpose of the uptake of thymocytes by TNCs is unknown. TNCs also have the capacity to present self-antigens, which implies that they may serve a function in the process of thymic education. We have recently reported the development of thymic nurse cell lines that have the ability to bind and internalize T cells. Here, we use one of these TNC lines to identify the thymocyte subpopulation involved in this internalization process. TNCs exposed to freshly isolated thymocytes bind and internalize CD4 and CD8 expressing thymocytes (CD4+CD8+ or double positives) exclusively. More specifically, a subset of the double-positive thymocyte pop ulation displayed binding capacity. These double-positive cells express cell surface a@ type T cell antigen receptor (TCR), as well as CD3r. Binding was not inhibited in the presences of antibodies against CD3, CD4, CD8, Class I antigens, or Class II antigens. These results describe two significant events in T cell development. First, TNCs exclusively bind and internalize a subset of &I TCR expressing double-positive T cells. Also, binding is facilitated through a mechanism other than TCR recognition of major histocompatibility complex antigens. This suggests that thymocyte internalization may be independent of the process used by TNCs to present self-antigen. o 1992 Academic Press, Inc.

Research paper thumbnail of The immortalization of thymic nurse cells by SV40 virus

Cellular Immunology, 1991

Thymic nurse cells (TNCs) are stromal elements that contain between 20 and 200 T cells within the... more Thymic nurse cells (TNCs) are stromal elements that contain between 20 and 200 T cells within their cytoplasm. Because of this unique feature they are believed to play a role in thymocyte development. Unfortunately, it has been difficult to obtain pure TNCs in quantities sufficient for extensive evaluation of their thymic function. As a result, only a limited amount of information is available that characterizes TNCs or the T cell population(s) found within their cytoplasm. We have now used SV40 to infect and immortalize TNCs from C57BL/6 mice. SV40-transformed TNCs were found to specifically bind and internalize cells from an immature thymocyte line isolated in our laboratory. These results describe a method of obtaining pure populations of TNCs for future studies of their thymic function, and suggest that binding to specific subpopulations of lymphoblasts may be necessary for internalization. 0 1991 Academic PXSS, IIIC.

Research paper thumbnail of Bone Marrow-Derived Cells Contribute to the Maintenance of Thymic Stroma including TECs

Journal of Immunology Research

In paradox to critical functions for T-cell selection and self-tolerance, the thymus undergoes pr... more In paradox to critical functions for T-cell selection and self-tolerance, the thymus undergoes profound age-associated atrophy and loss of T-cell function, further enhanced by cancer therapies. Identifying thymic epithelial progenitor populations capable of forming functional thymic tissue will be critical in understanding thymic epithelial cell (TEC) ontogeny and designing strategies to reverse involution. We identified a new population of progenitor cells, present in both the thymus and bone marrow (BM) of mice, that coexpress the hematopoietic marker CD45 and the definitive thymic epithelial marker EpCAM and maintain the capacity to form functional thymic tissue. Confocal analysis and qRT-PCR of sorted cells from both BM and thymus confirmed coexpression of CD45 and EpCAM. Grafting of C57BL/6 fetal thymi under the kidney capsule of H2BGFP transgenic mice revealed that peripheral CD45+ EpCAM+ GFP-expressing cells migrate into the developing thymus and contribute to both TECs and F...

Research paper thumbnail of The identification of thymic nurse cells in vivo and the role of cytoskeletal proteins in thymocyte internalization

Cellular Immunology, 2004

Research paper thumbnail of Questionable Thymic Nurse Cell

Microbiology and Molecular Biology Reviews, 2001

SUMMARY Since their discovery in 1980, thymic nurse cells (TNCs) have been controversial. Questio... more SUMMARY Since their discovery in 1980, thymic nurse cells (TNCs) have been controversial. Questions pertaining to the existence of the TNC as a “unit” cell with thymocytes completely enclosed within its cytoplasm were the focus of initial debates. Early skeptics proposed the multicellular complex to be an artifact of the procedures used to isolate TNCs from the thymus. Since that time, TNCs have been found in fish, frogs, tadpoles, chickens, sheep, pigs, rats, mice, and humans. Their evolutionary conservation throughout the animal kingdom relieved most speculations about the existence of TNCs and at the same time demonstrated their apparent importance to the thymus and T-cell development. In this review we will discuss and debate reports that describe (i) the organization or structure of TNCs, (ii) the thymocyte subset(s) found within the cytoplasm of TNCs and their uptake and release, and (iii) the function of this fascinating multicellular interaction that occurs during the proces...

Research paper thumbnail of DKK1 mediated inhibition of Wnt signaling in postnatal mice leads to loss of TEC progenitors and thymic degeneration. PLoS One. 2010; 5: e9062

Background: Thymic epithelial cell (TEC) microenvironments are essential for the recruitment of T... more Background: Thymic epithelial cell (TEC) microenvironments are essential for the recruitment of T cell precursors from the bone marrow, as well as the subsequent expansion and selection of thymocytes resulting in a mature self-tolerant T cell repertoire. The molecular mechanisms, which control both the initial development and subsequent maintenance of these critical microenvironments, are poorly defined. Wnt signaling has been shown to be important to the development of several epithelial tissues and organs. Regulation of Wnt signaling has also been shown to impact both early thymocyte and thymic epithelial development. However, early blocks in thymic organogenesis or death of the mice have prevented analysis of a role of canonical Wnt signaling in the maintenance of TECs in the postnatal thymus. Methodology/Principal Findings: Here we demonstrate that tetracycline-regulated expression of the canonical Wnt inhibitor DKK1 in TECs localized in both the cortex and medulla of adult mice...

Research paper thumbnail of Bone Marrow-Derived Cells Contribute to the Maintenance of Thymic Stroma including Thymic Epithelial Cells

In paradox to critical functions for T-cell selection and self-tolerance, the thymus undergoes pr... more In paradox to critical functions for T-cell selection and self-tolerance, the thymus undergoes profound age-associated atrophy and loss of T-cell function, which are further enhanced by cancer therapies. Identification of thymic epithelial progenitor populations capable of forming functional thymic tissue will be critical in understanding thymic epithelial cell (TEC) ontogeny and designing strategies to reverse involution. We identified a new population of progenitor cells, present in both thymus and bone marrow (BM), that co-express the hematopoietic marker CD45 and the definitive thymic epithelial marker EpCAM and maintains the capacity to form functional thymic tissue. Confocal analysis and qRT-PCR of sorted cells from both BM and thymus confirmed co-expression of CD45 and EpCAM. Grafting of C57BL/6 fetal thymi under the kidney capsule of H2BGFP transgenic mice revealed that peripheral CD45+ EpCAM+ GFP-expressing cells migrate into the developing thymus and contribute to both TEC...

Research paper thumbnail of A multipotent mesenchymal stem cell-like population in the postnatal thymus (P4466)

The Journal of Immunology, May 1, 2013

Research paper thumbnail of Hyperoxia and Regulatory T cell (Treg) development in neonatal mice Hardik Patel1, Angela Leon Hernandez1, Mark Pezzano2 and Mohamed Ahmed1 1Neonatology Research Lab, The Feinstein Institute for Medical Research, Manhasset, NY. 2Department of Biology, The City College of NY, New York, NY (LB546)

The Faseb Journal, Apr 1, 2014

Research paper thumbnail of Research Centers in Minority Institutions (RCMI)

Cellular and molecular biology (Noisy-le-Grand, France), 2003

The Research Centers in Minority Institutions (RCMI) Program was initiated in the United States o... more The Research Centers in Minority Institutions (RCMI) Program was initiated in the United States of America in 1985 as a congressionally mandated program. The mission of the RCMI Program is to expand the national capacity for the conduct of biomedical and behavioral research by developing the research infrastructure at institutions granting doctoral degrees in health or health-related sciences, that have 50% or greater enrollment of minorities (African Americans, Hispanics, Native Hawaiians and Pacific Islanders, Native Americans and Alaska Natives) that are underrepresented in the biomedical sciences. The program administration is based in the National Center for Research Resources (NCRR), at the National Institutes of Health (NIH), an agency of the Department of Health and Human Services (DHHS). Since its inception, the program has provided critical resources (core research laboratories, equipment, personnel, supplies, etc.) at each of the RCMI-funded institutions. This article is ...

Research paper thumbnail of TNF and Fas-induced apoptosis during negative selection in thymic nurse cells

Ethnicity & disease, 2001

Apoptosis of thymocytes associated with thymic nurse cells (TNCs) has been well-documented. TNCs ... more Apoptosis of thymocytes associated with thymic nurse cells (TNCs) has been well-documented. TNCs selectively bind and internalize immature alphabeta TCRlo CD4+ CD8+ thymocytes in vitro. A subset of the internalized population matures to the alphabeta TCRhi CD69hi stage of development while the fraction that remains within the cytoplasm dies through the process of apoptosis. Negative selection by thymic cortical epithelial cells has been reported, but little is known about the apoptotic pathway(s) employed to facilitate the death signal. Using the TNC line tsTNC-1 that was reported earlier to maintain the ability to internalize alphabeta TCRlo CD4+ CD8+ cells in vitro, we investigated the role of Fas and TNFalpha in TNC-induced apoptosis. Our initial studies revealed that tsTNC-1 cells express both FasL and TNFalpha apoptosis of triple positive cells was shown to be reduced approximately 50% in co-cultures of tsTNC-1 cells and thymocytes in the presence of either anti-TNFalpha or Fas...

Research paper thumbnail of Dkk1 mediated inhibition of Wnt Signaling in postnatal mice leads to loss of TEC progenitors and thymic degeneration (36.32)

Journal of Immunology, Apr 1, 2010

Background: Thymic epithelial cell (TEC) microenvironments are essential for the recruitment of T... more Background: Thymic epithelial cell (TEC) microenvironments are essential for the recruitment of T cell precursors from the bone marrow, as well as the subsequent expansion and selection of thymocytes resulting in a mature self-tolerant T cell repertoire. The molecular mechanisms, which control both the initial development and subsequent maintenance of these critical microenvironments, are poorly defined. Wnt signaling has been shown to be important to the development of several epithelial tissues and organs. Regulation of Wnt signaling has also been shown to impact both early thymocyte and thymic epithelial development. However, early blocks in thymic organogenesis or death of the mice have prevented analysis of a role of canonical Wnt signaling in the maintenance of TECs in the postnatal thymus. Methodology/Principal Findings: Here we demonstrate that tetracycline-regulated expression of the canonical Wnt inhibitor DKK1 in TECs localized in both the cortex and medulla of adult mice, results in rapid thymic degeneration characterized by a loss of DNP63 + Foxn1 + and Aire + TECs, loss of K5K8DP TECs thought to represent or contain an immature TEC progenitor, decreased TEC proliferation and the development of cystic structures, similar to an aged thymus. Removal of DKK1 from DKK1-involuted mice results in full recovery, suggesting that canonical Wnt signaling is required for the differentiation or proliferation of TEC populations needed for maintenance of properly organized adult thymic epithelial microenvironments. Conclusions/Significance: Taken together, the results of this study demonstrate that canonical Wnt signaling within TECs is required for the maintenance of epithelial microenvironments in the postnatal thymus, possibly through effects on TEC progenitor/stem cell populations. Downstream targets of Wnt signaling, which are responsible for maintenance of these TEC progenitors may provide useful targets for therapies aimed at counteracting age associated thymic involution or the premature thymic degeneration associated with cancer therapy and bone marrow transplants.

Research paper thumbnail of The Research Centers in Minority Institutions (RCMI) Translational Research Network: Building and Sustaining Capacity for Multi-Site Basic Biomedical, Clinical and Behavioral Research

Ethnicity & Disease, Feb 21, 2019

Services (DHHS) action plan to reduce racial and ethnic health disparities emphasizes the importa... more Services (DHHS) action plan to reduce racial and ethnic health disparities emphasizes the importance of a diverse workforce. 1 A growing field of investigation has unveiled the

Research paper thumbnail of Bone marrow-derived cells contribute to the maintenance of thymic stroma including thymic epithelial cells

Journal of Immunology, May 1, 2020

Research paper thumbnail of Wnt signaling during thymic involution and reconstitution. (HEM7P.226)

The Journal of Immunology

Despite its critical role in T-cell development, the thymus undergoes profound age-related involu... more Despite its critical role in T-cell development, the thymus undergoes profound age-related involution. Inhibition of Wnt signaling in thymic epithelium (TECs) leads to rapid involution. Lack of a Wnt reporter that was functional in TECs hindered characterization of Wnt signaling during TEC ontogeny. Using the TCF/LEF-H2BGFP Wnt reporter mouse, TECs undergoing active Wnt signaling were characterized during different stages of thymic aging and recovery. In the postnatal thymus, H2BGFP expression was restricted to TECs in the medulla and CMJ including 60% of the Aire-expressing mTECs, suggesting a role for Wnt signaling in the development of this critical TEC subset. Comparison of the TECs undergoing Wnt signaling in old versus young thymus revealed an increase in the frequency of TECs undergoing Wnt signaling even though overall TEC numbers decreased significantly with age. The decrease in both total TECs and TECs undergoing Wnt signaling was most apparent in the UEA1hi mTEC subset an...

Research paper thumbnail of Decision letter: Fine-tuning of β-catenin in mouse thymic epithelial cells is required for postnatal T-cell development

Research paper thumbnail of Content Alerts

This article cites 57 articles, 11 of which can be accessed free at:

Research paper thumbnail of Thymic Nurse Cell Multicellular Complexes in HY-TCR Transgenic Mice Demonstrate Their Association with MHC Restriction

Experimental Biology and Medicine, 2007

This study examines thymic nurse cell (TNC) function during T-cell development. It has been sugge... more This study examines thymic nurse cell (TNC) function during T-cell development. It has been suggested that TNCs function in the removal of nonfunctional and/or apoptotic thymocytes and do not participate in major histocompatibility complex restriction. We analyzed TNCs isolated from both normal C57BL/6 mice and C57BL/6 TgN (TCRHY) mice (HY-TCR transgenic mice). Using confocal microscopic analyses of TNCs isolated from C57BL/6 animals, we showed that 75%–78% of the enclosed thymocyte subset was viable, and 87%–90% of these cells expressed both CD4 and CD8. CD4 and CD8 also were expressed on TNC thymocytes isolated from both male and female HY-TCR transgenic mice. The transgenic female thymus was shown to have 17 times more TNCs per milligram of thymus than the transgenic male thymus. TNCs from HY-TCR transgenic females were 8–10 μm larger than transgenic male TNCs, and the female TNCs contained five times more thymocytes within intracytoplasmic vacuoles, with less than 4% apoptosis. ...

Research paper thumbnail of The Wnt Signaling Antagonist Kremen1 is Required for Development of Thymic Architecture

Clinical and Developmental Immunology, 2006

Wnt signaling has been reported to regulate thymocyte proliferation and selection at several stag... more Wnt signaling has been reported to regulate thymocyte proliferation and selection at several stages during T cell ontogeny, as well as the expression ofFoxN1in thymic epithelial cells (TECs). Kremen1 (Krm1) is a negative regulator of the canonical Wnt signaling pathway, and functions together with the secreted Wnt inhibitor Dickkopf (Dkk) by competing for the lipoprotein receptor-related protein (LRP)-6 co-receptor for Wnts. Herekrm1knockout mice were used to examinekrm1expression in the thymus and its function in thymocyte and TEC development.krm1expression was detected in both cortical and medullary TEC subsets, as well as in immature thymocyte subsets, beginning at the CD25+CD44+ (DN2) stage and continuing until the CD4+CD8+(DP) stage. Neonatal mice show elevated expression ofkrm1in all TEC subsets.krm1− / −mice exhibit a severe defect in thymic cortical architecture, including large epithelial free regions. Much of the epithelial component remains at an immature Keratin 5+(K5) K...

Research paper thumbnail of Circulating Macrophages as Well as Developing Thymocytes Are Enclosed within Thymic Nurse Cells

Cellular Immunology, 2001

Both thymic nurse cells (TNCs) and macrophages have been reported to function as antigen-presenti... more Both thymic nurse cells (TNCs) and macrophages have been reported to function as antigen-presenting cells during the process of MHC restriction. Negative selection, which results in the apoptosis of potentially autoreactive thymocytes, is believed to be associated with both macrophages and TNCs in the cortex. Both cell types have also been reported to ingest thymocytes undergoing positive and negative selection. However, macrophages ingest apoptotic thymocytes, while TNCs have been shown to internalize viable cells. A subset of the TNC-engulfed population is allowed to mature and is released, while the remaining fraction becomes apoptotic and is absorbed within the TNC cytoplasm through lysosomal activity. A recent report described a subset of rat TNCs that contain macrophages as well as thymocytes within their cytoplasm. We examined freshly isolated TNCs from C57BL/6 mice and found that, of the TNC population recovered, 1.7% contained macrophages within its cytoplasm. There also were macrophages tightly bound but not internalized into the multicellular structure at a rate of 2.9%. The total association of macrophages with TNCs was approximately 4.6%. This unique association of macrophages with TNCs was also observed in vitro when freshly isolated thymocytes (containing macrophages) were added to cultures of cells from the TNC cell line tsTNC-1. The macrophage-TNC interaction was found to be dynamic, with macrophages moving rapidly into and out of TNCs containing cytoplasmic thymocytes. Macrophages within TNCs showed a close association with cytoplasmic thymocytes. We then labeled peritoneal macrophages with CFDA SE, a cell tracking dye, and returned them to the mouse peritoneum. Within 1 h, labeled macrophages were detectable in the thymus. This is the first investigation to show a direct interaction between peripheral macrophages and TNCs. These results suggest that TNCs and macrophages work together as antigen-presenting cells.

Research paper thumbnail of Thymic nurse cells exclusively bind and internalize CD4+CD8+ thymocytes

Cellular Immunology, 1992

Thymic nurse cells (TNC) contain 20-200 thymocytes within specialized vacuoles in their cytoplasm... more Thymic nurse cells (TNC) contain 20-200 thymocytes within specialized vacuoles in their cytoplasm. The purpose of the uptake of thymocytes by TNCs is unknown. TNCs also have the capacity to present self-antigens, which implies that they may serve a function in the process of thymic education. We have recently reported the development of thymic nurse cell lines that have the ability to bind and internalize T cells. Here, we use one of these TNC lines to identify the thymocyte subpopulation involved in this internalization process. TNCs exposed to freshly isolated thymocytes bind and internalize CD4 and CD8 expressing thymocytes (CD4+CD8+ or double positives) exclusively. More specifically, a subset of the double-positive thymocyte pop ulation displayed binding capacity. These double-positive cells express cell surface a@ type T cell antigen receptor (TCR), as well as CD3r. Binding was not inhibited in the presences of antibodies against CD3, CD4, CD8, Class I antigens, or Class II antigens. These results describe two significant events in T cell development. First, TNCs exclusively bind and internalize a subset of &I TCR expressing double-positive T cells. Also, binding is facilitated through a mechanism other than TCR recognition of major histocompatibility complex antigens. This suggests that thymocyte internalization may be independent of the process used by TNCs to present self-antigen. o 1992 Academic Press, Inc.

Research paper thumbnail of The immortalization of thymic nurse cells by SV40 virus

Cellular Immunology, 1991

Thymic nurse cells (TNCs) are stromal elements that contain between 20 and 200 T cells within the... more Thymic nurse cells (TNCs) are stromal elements that contain between 20 and 200 T cells within their cytoplasm. Because of this unique feature they are believed to play a role in thymocyte development. Unfortunately, it has been difficult to obtain pure TNCs in quantities sufficient for extensive evaluation of their thymic function. As a result, only a limited amount of information is available that characterizes TNCs or the T cell population(s) found within their cytoplasm. We have now used SV40 to infect and immortalize TNCs from C57BL/6 mice. SV40-transformed TNCs were found to specifically bind and internalize cells from an immature thymocyte line isolated in our laboratory. These results describe a method of obtaining pure populations of TNCs for future studies of their thymic function, and suggest that binding to specific subpopulations of lymphoblasts may be necessary for internalization. 0 1991 Academic PXSS, IIIC.

Research paper thumbnail of Bone Marrow-Derived Cells Contribute to the Maintenance of Thymic Stroma including TECs

Journal of Immunology Research

In paradox to critical functions for T-cell selection and self-tolerance, the thymus undergoes pr... more In paradox to critical functions for T-cell selection and self-tolerance, the thymus undergoes profound age-associated atrophy and loss of T-cell function, further enhanced by cancer therapies. Identifying thymic epithelial progenitor populations capable of forming functional thymic tissue will be critical in understanding thymic epithelial cell (TEC) ontogeny and designing strategies to reverse involution. We identified a new population of progenitor cells, present in both the thymus and bone marrow (BM) of mice, that coexpress the hematopoietic marker CD45 and the definitive thymic epithelial marker EpCAM and maintain the capacity to form functional thymic tissue. Confocal analysis and qRT-PCR of sorted cells from both BM and thymus confirmed coexpression of CD45 and EpCAM. Grafting of C57BL/6 fetal thymi under the kidney capsule of H2BGFP transgenic mice revealed that peripheral CD45+ EpCAM+ GFP-expressing cells migrate into the developing thymus and contribute to both TECs and F...

Research paper thumbnail of The identification of thymic nurse cells in vivo and the role of cytoskeletal proteins in thymocyte internalization

Cellular Immunology, 2004

Research paper thumbnail of Questionable Thymic Nurse Cell

Microbiology and Molecular Biology Reviews, 2001

SUMMARY Since their discovery in 1980, thymic nurse cells (TNCs) have been controversial. Questio... more SUMMARY Since their discovery in 1980, thymic nurse cells (TNCs) have been controversial. Questions pertaining to the existence of the TNC as a “unit” cell with thymocytes completely enclosed within its cytoplasm were the focus of initial debates. Early skeptics proposed the multicellular complex to be an artifact of the procedures used to isolate TNCs from the thymus. Since that time, TNCs have been found in fish, frogs, tadpoles, chickens, sheep, pigs, rats, mice, and humans. Their evolutionary conservation throughout the animal kingdom relieved most speculations about the existence of TNCs and at the same time demonstrated their apparent importance to the thymus and T-cell development. In this review we will discuss and debate reports that describe (i) the organization or structure of TNCs, (ii) the thymocyte subset(s) found within the cytoplasm of TNCs and their uptake and release, and (iii) the function of this fascinating multicellular interaction that occurs during the proces...

Research paper thumbnail of DKK1 mediated inhibition of Wnt signaling in postnatal mice leads to loss of TEC progenitors and thymic degeneration. PLoS One. 2010; 5: e9062

Background: Thymic epithelial cell (TEC) microenvironments are essential for the recruitment of T... more Background: Thymic epithelial cell (TEC) microenvironments are essential for the recruitment of T cell precursors from the bone marrow, as well as the subsequent expansion and selection of thymocytes resulting in a mature self-tolerant T cell repertoire. The molecular mechanisms, which control both the initial development and subsequent maintenance of these critical microenvironments, are poorly defined. Wnt signaling has been shown to be important to the development of several epithelial tissues and organs. Regulation of Wnt signaling has also been shown to impact both early thymocyte and thymic epithelial development. However, early blocks in thymic organogenesis or death of the mice have prevented analysis of a role of canonical Wnt signaling in the maintenance of TECs in the postnatal thymus. Methodology/Principal Findings: Here we demonstrate that tetracycline-regulated expression of the canonical Wnt inhibitor DKK1 in TECs localized in both the cortex and medulla of adult mice...

Research paper thumbnail of Bone Marrow-Derived Cells Contribute to the Maintenance of Thymic Stroma including Thymic Epithelial Cells

In paradox to critical functions for T-cell selection and self-tolerance, the thymus undergoes pr... more In paradox to critical functions for T-cell selection and self-tolerance, the thymus undergoes profound age-associated atrophy and loss of T-cell function, which are further enhanced by cancer therapies. Identification of thymic epithelial progenitor populations capable of forming functional thymic tissue will be critical in understanding thymic epithelial cell (TEC) ontogeny and designing strategies to reverse involution. We identified a new population of progenitor cells, present in both thymus and bone marrow (BM), that co-express the hematopoietic marker CD45 and the definitive thymic epithelial marker EpCAM and maintains the capacity to form functional thymic tissue. Confocal analysis and qRT-PCR of sorted cells from both BM and thymus confirmed co-expression of CD45 and EpCAM. Grafting of C57BL/6 fetal thymi under the kidney capsule of H2BGFP transgenic mice revealed that peripheral CD45+ EpCAM+ GFP-expressing cells migrate into the developing thymus and contribute to both TEC...

Research paper thumbnail of A multipotent mesenchymal stem cell-like population in the postnatal thymus (P4466)

The Journal of Immunology, May 1, 2013

Research paper thumbnail of Hyperoxia and Regulatory T cell (Treg) development in neonatal mice Hardik Patel1, Angela Leon Hernandez1, Mark Pezzano2 and Mohamed Ahmed1 1Neonatology Research Lab, The Feinstein Institute for Medical Research, Manhasset, NY. 2Department of Biology, The City College of NY, New York, NY (LB546)

The Faseb Journal, Apr 1, 2014

Research paper thumbnail of Research Centers in Minority Institutions (RCMI)

Cellular and molecular biology (Noisy-le-Grand, France), 2003

The Research Centers in Minority Institutions (RCMI) Program was initiated in the United States o... more The Research Centers in Minority Institutions (RCMI) Program was initiated in the United States of America in 1985 as a congressionally mandated program. The mission of the RCMI Program is to expand the national capacity for the conduct of biomedical and behavioral research by developing the research infrastructure at institutions granting doctoral degrees in health or health-related sciences, that have 50% or greater enrollment of minorities (African Americans, Hispanics, Native Hawaiians and Pacific Islanders, Native Americans and Alaska Natives) that are underrepresented in the biomedical sciences. The program administration is based in the National Center for Research Resources (NCRR), at the National Institutes of Health (NIH), an agency of the Department of Health and Human Services (DHHS). Since its inception, the program has provided critical resources (core research laboratories, equipment, personnel, supplies, etc.) at each of the RCMI-funded institutions. This article is ...

Research paper thumbnail of TNF and Fas-induced apoptosis during negative selection in thymic nurse cells

Ethnicity & disease, 2001

Apoptosis of thymocytes associated with thymic nurse cells (TNCs) has been well-documented. TNCs ... more Apoptosis of thymocytes associated with thymic nurse cells (TNCs) has been well-documented. TNCs selectively bind and internalize immature alphabeta TCRlo CD4+ CD8+ thymocytes in vitro. A subset of the internalized population matures to the alphabeta TCRhi CD69hi stage of development while the fraction that remains within the cytoplasm dies through the process of apoptosis. Negative selection by thymic cortical epithelial cells has been reported, but little is known about the apoptotic pathway(s) employed to facilitate the death signal. Using the TNC line tsTNC-1 that was reported earlier to maintain the ability to internalize alphabeta TCRlo CD4+ CD8+ cells in vitro, we investigated the role of Fas and TNFalpha in TNC-induced apoptosis. Our initial studies revealed that tsTNC-1 cells express both FasL and TNFalpha apoptosis of triple positive cells was shown to be reduced approximately 50% in co-cultures of tsTNC-1 cells and thymocytes in the presence of either anti-TNFalpha or Fas...