Anthony Defranco - Academia.edu (original) (raw)

Papers by Anthony Defranco

Journal of Biological Chemistry, 2005

Toll-like receptor (TLR) 3 and TLR7 are indispensable for host defense against viral infection by... more Toll-like receptor (TLR) 3 and TLR7 are indispensable for host defense against viral infection by recognizing virus-derived RNAs and are localized to intracellular membranes via an unknown mechanism. We recently reported experiments with chimeric Toll-like receptors that suggested that the subcellular distribution of TLRs may be defined by their transmembrane and/or cytoplasmic domains. Here we demonstrate that the intracellular localization of TLR3 is achieved by a 23-amino acid sequence (Glu(727) to Asp(749)) present in the linker region between the transmembrane domain and Toll-interleukin 1 receptor resistance (TIR) domain. In contrast, the intracellular localization of TLR7 is achieved by its transmembrane domain. These elements also targeted a heterologous type I transmembrane protein CD25 to the intracellular compartment that contained TLR3 and TLR7. Despite their using distinct regulatory elements for intracellular localization, TLR3 was found to co-localize with TLR7. In addition, TLR3 and TLR7 were preferentially localized near phagosomes containing apoptotic cell particles. These findings reveal that TLR3 and TLR7 contain unique targeting sequences, which differentially lead them to the same intracellular compartments and adjacent to phagosomes containing apoptotic cell particles, where these receptors may access their ligands for the induction of immune responses against viral infection.

Cross-linking of the B-cell antigen receptor (BCR) induces tyrosine phosphorylation of Shc, which... more Cross-linking of the B-cell antigen receptor (BCR) induces tyrosine phosphorylation of Shc, which is believed to lead to the activation of Ras. Previous work has shown that tyrosine-phosphorylated Shc forms complexes with another adapter protein, Grb2, and the Ras guanine nucleotide exchange factor SOS. Here, we demonstrate that phosphorylation of Shc by the hematopoietic cell-specific tyrosine kinase Syk induces binding

Journal of Crohn's and Colitis Supplements, 2008

severe active luminal CD, agreed upon by the panel experts (acute flare, hospitalized patient, wi... more severe active luminal CD, agreed upon by the panel experts (acute flare, hospitalized patient, without documented fistula or stenosis and who did not undergo surgery for abscess drainage or a fistulectomy). The various treatments were analyzed to determine the appropriateness of the medical decision, according to the EPACT criteria. Results: 84 (20%) patients met the inclusion criteria. Considering at least one appropriate (A) treatment as appropriate: 60 patients (71%) received an appropriate treatment, 24 patients (29%) an inappropriate treatment (I). Furthermore, in 87% of the cases with one appropriate treatment an additional mostly inappropriate treatment was added or continued. Detailed results are indicated in the table. Conclusion: In the EC-IBD IBD cohort, the treatment for severe active luminal CD was appropriate for more than 70% of the patients, but frequently an inappropriate treatment was continued or added, thus increasing the risk of adverse reactions, drugs interactions and costs Introduction: 5-Aminosalicylates (5-ASA) interfere in a dose dependent manner with thiopurines (6-MP/AZA) metabolism, increasing concentrations of 6TGN without changing MMP levels. In particular one of these metabolites, TGN-3triphospate, is associated with therapeutic efficacy. We performed a prospective pharmakinetic evaluation of thiopurine metabolites in IBD patients during steady-state AZA therapy under two different 5-ASA dosages. Methods: IBD patients on steady-state mono-therapy AZA for at least 8 weeks with normal routine laboratory control values were included in our study. Study-design comprehended four 4 week study periods in which two different dosages of 5-ASA were used (2 and 4 gr). Laboratory parameters, adverse events, 6-TG mono-, di-and triphosphate levels (6-TGMP/6-TGDP/6-TGTP), 6-MMP levels, 5-ASA and N-acetyl-5-aminosalicylic acid (N-5-ASA) levels were determined at each visit. Differences in metabolite concentrations were evaluated using the Wilcoxon Matched-Pairs Signed-Ranks Test. Results: 17 IBD patients were included (CD=11, UC=5, IC=1, 6 females and mean age 42 yr). Mean AZA dose at time of inclusion was 150 mg (= 2,0 mg/kg). Median baseline values of 6-TGDP, 6-TGTP and 6-MMPR before initiation of 5-ASA were 52, 319 and 1676 pmol/8x10 8 RBC respectively (ranges 13-192, 83-583 and 0-9837 pmol/8x10 8 RBC). As expected, no 5-ASA or N-acetyl-5-ASA was detected in the serum of any patient. Significant increase in 6-TGDP, 6-TGTP and total 6TGN levels was only observed after the first period of ASA co-administration (i.e. 2 gram ASA daily; see ). Median 6-TGTP levels rose with 28% to 482 pmol/8x108 RBC at t=2 after the first 5-ASA dosage regime, an absolute increase of 163 pmol/8x108 RBC (P<0,0002). Levels of 5-ASA and N-5-ASA were 175 and 1260 ng/ml at t=2, respectively. After the second scheme of 5-ASA (t=3), 6-TGTP levels reached median values of 483 pmol/8x108 RBC and did not differ from median values at t=2 (P=0,669). The 5-ASA and N-5-ASA levels at t=3 were 1295

European Journal of Immunology

Lyn, an Src-family protein tyrosine kinase expressed in B lymphocytes, contributes to initiation ... more Lyn, an Src-family protein tyrosine kinase expressed in B lymphocytes, contributes to initiation of BCR signaling and is also responsible for feedback inhibition of BCR signaling. Lyn-deficient mice have a decreased number of follicular B cells and also spontaneously develop a lupus-like autoimmunity. We used flow cytometric analysis, BrdU labeling and our mathematical models of B-cell population dynamics, to analyze how Lyn deficiency impacts B-cell maturation and survival. We found that Lyn-deficient transitional 1 (T1) cells develop normally, but T2 cells develop primarily from the T1 subset in the spleen and fail to also develop directly from BM immature B cells. Lyn-deficient T2 cells either mature to the follicular B-cell type at a close to normal rate, or die in this compartment rather than access the T3 anergic subset. The ≈ 40% of WT follicular cells that were short-lived exited primarily by joining the T3 anergic subset, whereas the ≈ 15% Lyn(-/-) follicular cells that wer...

Journal of immunology (Baltimore, Md. : 1950), 1992

Cross-linking of the B cell AgR results in activation of mature B cells and tolerization of immat... more Cross-linking of the B cell AgR results in activation of mature B cells and tolerization of immature B cells. The initial signaling events stimulated by membrane immunoglobulin (mIg) cross-linking are tyrosine phosphorylation of a number of proteins. Among the targets of mIg-induced tyrosine phosphorylation are the tyrosine kinases encoded by the lyn, blk, fyn, and syk genes, the mIg-associated proteins MB-1 and Ig-beta, phospholipase C-gamma 1 and -gamma 2, as well as many unidentified proteins. In this report we show that mIg cross-linking also regulates phosphatidylinositol 3-kinase (PtdIns 3-kinase), an enzyme that phosphorylates inositol phospholipids and plays a key role in mediating the effects of tyrosine kinases on growth control in fibroblasts. Cross-linking mIg on B lymphocytes greatly increased the amount of PtdIns 3-kinase activity which could be immunoprecipitated with anti-phosphotyrosine (anti-tyr(P) antibodies. This response was observed after mIg cross-linking in m...

European Journal of Immunology, 2015

In general, a long-lasting immune response to viruses is achieved when they are infectious and re... more In general, a long-lasting immune response to viruses is achieved when they are infectious and replication competent. In the mouse, the neutralizing antibody response to Friend murine leukemia virus is contributed by an allelic form of the enzyme Apobec3 (abbreviated A3). This is counterintuitive because A3 directly controls viremia before the onset of adaptive antiviral immune responses. It suggests that A3 also affects the antibody response directly. Here, we studied the relative size of cell populations of the adaptive immune system as a function of A3 activity. We created a transgenic mouse that expresses all seven human A3 enzymes and compared it to WT and mouse A3-deficient mice. A3 enzymes decreased the number of marginal zone B cells, but not the number of follicular B or T cells. When mouse A3 was knocked out, the retroelement hitchhiker-1 and sialyl transferases encoded by genes close to it were overexpressed three and two orders of magnitude, respectively. We suggest that A3 shifts the balance, from the fast antibody response mediated by marginal zone B cells with little affinity maturation, to a more sustained germinal center B-cell response, which drives affinity maturation and, thereby, a better neutralizing response.

Type I interferons (T1IFNs) are among the earliest cytokines produced during infections due to th... more Type I interferons (T1IFNs) are among the earliest cytokines produced during infections due to their direct regulation by innate immune signaling pathways. Reports have suggested that T1IFNs are produced during malaria infection, but little is known about the in vivo cellular origins of T1IFNs or their role in protection. We have found that in addition to plasmacytoid dendritic cells, splenic red pulp macrophages (RPMs) can generate significant quantities of T1IFNs in response to P. chabaudi infection in a TLR9-, MYD88-, and IRF7-dependent manner. Furthermore, T1IFNs regulate expression of interferon-stimulated genes redundantly with Interferon-gamma (IFNG), resulting in redundancy for resistance to experimental malaria infection. Despite their role in sensing and promoting immune responses to infection, we observe that RPMs are dispensable for control of parasitemia. Our results reveal that RPMs are early sentinels of malaria infection, but that effector mechanisms previously attributed to RPMs are not essential for control.

Macrophage Fc g receptors (Fc g Rs) mediate the uptake and destruction of antibody-coated vi- rus... more Macrophage Fc g receptors (Fc g Rs) mediate the uptake and destruction of antibody-coated vi- ruses, bacteria, and parasites. We examined Fc g R signaling and phagocytic function in bone marrow-derived macrophages from mutant mice lacking the major Src family kinases ex- pressed in these cells, Hck, Fgr, and Lyn. Many Fc g R-induced functional responses and signal- ing events

Summary Receptors on macrophages for the Fc region of IgG (Fc g R) mediate a number of responses ... more Summary Receptors on macrophages for the Fc region of IgG (Fc g R) mediate a number of responses important for host immunity. Signaling events necessary for these responses are likely initi- ated by the activation of Src-family and Syk-family tyrosine kinases after Fc g R cross-linking. Macrophages derived from Syk-deficient (Syk 2 ) mice were defective in phagocytosis of parti-

Bacterial lipopolysaccharide (LPS) elic- its responses by macrophages that help the body repel in... more Bacterial lipopolysaccharide (LPS) elic- its responses by macrophages that help the body repel infections. Recent evidence indicates that phosphatidylinositol 3-kinase (PI 3-kinase) may mediate some of these responses. Here, we show that exposing macrophages to LPS rapidly in- creased membrane-associated PI 3-kinase activity and also elevated p70 S6 kinase activity. Inhibitors of PI 3-kinase or the mammalian target of rapamy-

Circulation. Cardiovascular interventions, 2009

AVID (Angiography Versus Intravascular ultrasound-Directed stent placement) is a multicenter, ran... more AVID (Angiography Versus Intravascular ultrasound-Directed stent placement) is a multicenter, randomized controlled trial designed to assess the effect of intravascular ultrasound (IVUS)-directed stent placement on the 12-month rate of target lesion revascularization (TLR). After elective coronary stent placement and an optimal angiographic result (<10% stenosis), 800 patients were randomized to Angiography- or IVUS-directed therapy. Blinded IVUS was performed in the Angiography group without further therapy. In the IVUS group, IVUS criteria for optimal stent placement (<10% area stenosis, apposition, and absence of dissection) were applied. Final minimum stent area was 6.90+/-2.43 mm(2) in the Angiography group and 7.55+/-2.82 mm(2) in the IVUS group (P=0.001). In the IVUS group, only 37% with inadequate expansion (<90%) received further therapy. The 12-month TLR rate was 12.0% in the Angiography group and 8.1% in the IVUS group (P=0.08, 95% confidence level [CI], [-8.3% t...

Advances in Experimental Medicine and Biology, 1994

The antigen receptor of B lymphocytes (BCR) plays important roles in virtually every stage in the... more The antigen receptor of B lymphocytes (BCR) plays important roles in virtually every stage in the development, inactivation, or activation of B cells. The BCR is a complex of membrane immunoglobulin (mIg) and a heterodimer of two transmembrane polypeptides called Ig-alpha and Ig-beta. Site directed mutation of the mu immunoglobulin heavy chain has demonstrated that the mu transmembrane domain plays a key role in the assembly of mIgM with Ig-alpha/Ig-beta. In addition, there is a strong correlation between the ability of various mutant mIgM molecules to associate with Ig-alpha/Ig-beta and their ability to induce signal transduction reactions such as protein tyrosine phosphorylation and phosphoinositide breakdown. The cytoplasmic domains of Ig-alpha and Ig-beta share a region of limited homology with each other and with components of the T cell antigen receptor and of the Fc receptor. The presence of regions of the cytoplasmic domains of Ig-alpha or Ig-beta including this conserved amino acid sequence motif is sufficient to confer signaling function on chimeric transmembrane proteins. Both Ig-alpha and Ig-beta chimeras are capable of inducing all of the BCR signaling events tested. Based on these and related observations, we propose that the motifs act to initiate the BCR signaling reactions by binding and activating tyrosine kinases. Among the important events mediated by BCR signaling is induced expression of a series of genes referred to as early response genes. In B cells these include transcription factors and at least one component that regulates signaling events. One of these genes, c-myc, appears to play an important role in mediating apoptosis in B cells stimulated via the BCR complex.

Seminars in Immunology, 1998

The function of Lyn in B cell activation has been studied recently by examining the properties of... more The function of Lyn in B cell activation has been studied recently by examining the properties of B cells from mice in which the lyn gene has been inactivated by gene targeting. These mice show evidence of B cell hyperreactivity in vivo, as the number of B lymphoblastoid cells greatly increase with age, IgM levels increase by 10-fold or more, and autoantibodies to double-stranded DNA and other nuclear antigens become apparent. B cells from lyn yry mice also exhibit enhanced BCR-induced activation of MAP kinases, intracellular calcium elevation and proliferative responses in vitro. These phenomena may relate to participation of Lyn in events that serve to decrease B cell responses to antigen. Among the leading candidates for these suppressive events are the inhibition of B cell antigen receptor function by Fc␥ RIIb1 and by CD22. Although Lyn also participates positively in the initial events of B cell antigen receptor signal transduction, this function can also be supplied by other tyrosine kinases, presumably other Src-family kinases. In contrast, some aspects of inhibition by CD22 appear to be almost completely dependent upon Lyn and Fc␥ RIIb1 inhibition is also diminished in the absence of Lyn. Thus, the net effect of Lyn action is negative rather than positive for B cell activation. Key words: autoimmunity r CD22 r Fc␥ RIIb r Lyn r Src-family kinases ᮊ1998 Academic Press ACTIVATION OF B lymphocytes is initiated by contact Ž . of the B cell antigen receptor BCR with antigen and proceeds if the B cell receives additional stimulatory signals, which can include cytokines, membranebound molecules of helper T cells, such as CD40L, or polyclonal B cell activator molecules from bacterial cell walls. The extent and nature of required additio-From The George Williams Hooper Foundation,

Proceedings of the National Academy of Sciences, 1978

Certain cheU mutants of Salmonella show inverted chemotactic behavior, being repelled by attracta... more Certain cheU mutants of Salmonella show inverted chemotactic behavior, being repelled by attractants and attracted by repellents. Such a dramatic change in behavioral pattern woul seem at first glance to require drastic and complex alterations in the sensory processing system. In fact, the behavior can be explained by a simple shift in the level of a response regulator and the subtle effects of this shift on flagellar function. Flagella can exist in either a left-handed or a right-handed structure depending on applied torsion. Wild-type cells swim smoothly by counterclockwise rotation of a lefthanded helical bundle and tumble when the motors briefly re-

Proceedings of the National Academy of Sciences, 1996

Activation of macrophages by bacterial lipopolysaccharide (LPS) induces transcription of genes th... more Activation of macrophages by bacterial lipopolysaccharide (LPS) induces transcription of genes that encode for proinflammatory regulators of the immune response. Previous work has suggested that activation of the transcription factor activator protein 1 (AP-1) is one LPS-induced event that mediates this response. Consistent with this notion, we found that LPS stimulated AP-1-mediated transcription of a transfected reporter gene in the murine macrophage cell line RAW 264.7. As AP-1 activity is regulated in part by activation of the c-Jun N-terminal kinase (JNK), which phosphorylates and subsequently increases the transcriptional activity of c-Jun, we examined whether LPS treatment of macrophages resulted in activation of this kinase. LPS treatment of RAW 264.7 cells, murine bone marrow-derived macrophages, and the human monocyte cell line THP-1 resulted in rapid activation of the p46 and p54 isoforms of JNK. Treatment with wild-type and rough mutant forms of LPS and synthetic lipid A resulted in JNK activation, while pretreatment with the tyrosine kinase inhibitor herbimycin A inhibited this response. Binding of LPS-LPS binding protein (LBP) complexes to CD14, a surface receptor that mediates many LPS responses, was found to be crucial, as pretreatment of THP-1 cells with the monoclonal antibody 60b, which blocks this binding, inhibited JNK activation. These results suggest that LPS activation of JNK in monocyte/macrophage cells is a CD14- and protein tyrosine phosphorylation-dependent event that may mediate the early activation of AP-1 in regulating LPS-triggered gene induction.

Nature Immunology, 2011

Dendritic cells (DCs), known to support immune activation during infections, may also regulate im... more Dendritic cells (DCs), known to support immune activation during infections, may also regulate immune homeostasis in resting animals. Here we show that mice lacking A20 specifically in DCs spontaneously exhibited DC activation and expansion of activated T cells. DC-specific epistasis experiments using A20 fl/fl Myd88 fl/fl Cd11c-Cre compound mice revealed that A20 restricts both MyD88-independent signals, which drive DC and T cell activation, and MyD88-dependent signals, which drive T cell expansion. In addition, A20 fl/fl Cd11c-Cre mice spontaneously developed lymphocyte-dependent colitis, sero-negative ankylosing arthritis and enthesitis, conditions stereotypical for human inflammatory bowel disease (IBD). These findings indicate that DCs require A20 to preserve immune quiescence and suggest that A20-dependent DC functions may underlie IBD and IBD-associated arthritides.

Nature, 1990

Signalling by membrane immunoglobulin, the B-lymphocyte antigen receptor, regulates B-cell matura... more Signalling by membrane immunoglobulin, the B-lymphocyte antigen receptor, regulates B-cell maturation and activation. Crosslinking of membrane immunoglobulin by antigen or by anti-immunoglobulin antibodies inactivates immature B cells, eliminating many of the B cells capable of producing auto-antibodies. By contrast, crosslinking of membrane immunoglobulin promotes activation of mature B cells for clonal expansion and antibody production against foreign antigens. Crosslinking membrane IgM on the immature B-cell line WEHI-231 induces growth arrest. This response may be analogous to the deletion or inactivation of immature B cells that is induced by antigen or anti-IgM antibodies. Membrane immunoglobulin crosslinking stimulates phosphoinositide hydrolysis, which leads to increases in intracellular calcium and activation of protein kinase C. The induced phosphoinositide breakdown is important for inhibiting WEHI-231 growth (ref. 7 and D. Page, M.R.G., K. Fahey, L. Matsuuchi and A.L.D., manuscript submitted for publication), but may not be sufficient, as agents that elevate calcium and activate protein kinase C cause only partial growth arrest. We now show that in both mature splenic B cells and the immature B-cell line WEHI-231 crosslinking membrane immunoglobulin also stimulates phosphorylation of protein tyrosine, a reaction that has been implicated as a key regulator of cell growth. Most of these phosphorylations were not a consequence of the phosphoinositide pathway. Thus, tyrosine phosphorylation is a second mode of transmembrane signalling by membrane immunoglobulin.

Mayo Clinic Proceedings, 2014

To determine how all-cause hospitalizations within 12 months preceding an index heart failure (HF... more To determine how all-cause hospitalizations within 12 months preceding an index heart failure (HF) hospitalization affect risk stratification for 30-day all-cause readmission. Early readmission of inpatients with HF is challenging to predict, yet this outcome is used to compare hospital performance and guide reimbursement. Most risk models do not consider the potentially important variable of prior admissions. We analyzed Medicare inpatients with HF aged 66 years or older admitted to 14 Michigan community hospitals from October 1, 2002, to March 31, 2003, and from January 1 to June 30, 2004. Clinical data were obtained from admission charts, hospitalization dates from Centers for Medicare &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp; Medicaid Services (CMS) claims, and mortality dates from the Social Security Death Index. We used mixed-effects logistic regression and reclassification indices to evaluate the ability of a CMS chart-based readmission risk model, prior admissions, and their combination to predict 30-day readmission in survivors of the index HF hospitalization. Of 1807 patients, 43 (2.4%) died during the index admission; 476 of 1764 survivors (27%) were readmitted 30 or fewer days after discharge. Adjusted for the CMS readmission model, prior admissions significantly increased the odds of 30-day readmission (1 vs 0: odds ratio, 4.67; 95% CI, 3.37-6.46; ≥2 vs 0: odds ratio, 6.49; 95% CI, 4.93-8.55; both P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;.001), improved model discrimination (c statistic, 0.61-0.74, P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;.001), and reclassified many patients (net reclassification index, 0.40; integrated discrimination index, 0.12). In Medicare inpatients with HF, prior all-cause admissions strongly increase all-cause readmission risk and markedly improve risk stratification for 30-day readmission.