Hussein Ghamlouch | Université de Picardie Jules Verne (original) (raw)

Papers by Hussein Ghamlouch

Research paper thumbnail of TLR9 ligand (CpG oligodeoxynucleotide) induces CLL B-cells to differentiate into CD20+ antibody-secreting cells

† Jean-Pierre Marolleau and Brigitte Gubler have contributed equally to this work.

Research paper thumbnail of Phorbol myristate acetate, but not CD40L, induces the differentiation of CLL B cells into Ab-secreting cells

In this study, we investigated the capacity of chronic lymphocytic leukemia (CLL) B cells to unde... more In this study, we investigated the capacity of chronic lymphocytic leukemia (CLL) B cells to undergo terminal differentiation into Ig-secreting plasma cells in T cell-independent and T cell-dependent responses. We used a two-step model involving stimulation with phorbol myristate acetate (PMA) and CD40L, together with cytokines (PMA/c and CD40L/c), for 7 days. We describe immunophenotypic modifications, changes in the levels of mRNA and protein for transcription factors and morphological and functional events occurring during the differentiation of CLL B cells into antibody-secreting cells (ASCs). The induction of differentiation differed significantly between the CD40L/c and PMA/c culture systems. The PMA/c culture system allowed CLL B cells to differentiate into IgM-secreting cells with an immunophenotype and molecular profile resembling those of preplasmablasts. By contrast, CD40L/c-stimulated cells had a phenotype and morphology similar to those of activated B cells and resembling those of the CLL B cells residing in the lymph node and bone marrow. These data suggest that the CLL B cells are not frozen permanently at a stage of differentiation and are able to differentiate into ASCs as appropriate stimulation are provided. The data presented here raise questions about the molecular processes and stimulation required for CLL B-cell differentiation and about the inability of CD40 ligand to induce differentiation of the CLL B cells.

Research paper thumbnail of Characterization of a new V gene replacement in the absence of activation-induced cytidine deaminase and its contribution to human B-cell receptor diversity.

In B cells, B-cell receptor (BCR) immunoglobulin revision is a common route for modifying unwante... more In B cells, B-cell receptor (BCR) immunoglobulin revision is a common route for modifying unwanted antibody specificities via a mechanism called VH replacement. This in vivo process, mostly affecting heavy-chain rearrangement, involves the replacement of all or part of a previously rearranged IGHV gene with another germline IGHV gene located upstream. Two different mechanisms of IGHV replacement have been reported: type 1, involving the recombination activating genes complex and requiring a framework region 3 internal recombination signal; and type 2, involving an unidentified mechanism different from that of type 1. In the case of light-chain loci, BCR immunoglobulin editing ensures that a second V-J rearrangement occurs. This helps to maintain tolerance, by generating a novel BCR with a new antigenic specificity. We report that human B cells can, surprisingly, undergo type 2 replacement associated with j light-chain rearrangements. The de novo IGKV-IGKJ products result from the partial replacement of a previously rearranged IGKV gene by a new germline IGKV gene, in-frame and without deletion or addition of nucleotides. There are wrcy/rgyw motifs at the 'IGKV donor-IGKV recipient chimera junction' as described for type 2 IGHV replacement, but activation-induced cytidine deaminase (AID) expression was not detected. This unusual mechanism of homologous recombination seems to be a variant of gene conversion-like recombination, which does not require AID. The recombination phenomenon described here provides new insight into immunoglobulin locus recombination and BCR immunoglobulin repertoire diversity.

Research paper thumbnail of A Combination of Cytokines Rescues Highly Purified Leukemic CLL B-Cells from Spontaneous Apoptosis In Vitro

B-chronic lymphocytic leukemia (B-CLL), the most common human leukemia, is characterized by predo... more B-chronic lymphocytic leukemia (B-CLL), the most common human leukemia, is characterized by predominantly nondividing malignant mature CD5+ B lymphocytes with an apoptosis defect. Various microenvironmental stimuli confer a growth advantage on these leukemic cells and extend their survival in vivo. Nevertheless, when cultured in vitro, CLL B-cells rapidly die from apoptosis. Certain cytokines may extend the survival capacity of CLL B-cells in vitro and individual antiapoptotic effects of several cytokines have been reported. The potential cumulative effect of such cytokines has not been studied. We therefore investigated the effects on CLL B-cells survival in vitro of humoral factors, polyclonal lymphocyte activators and a combination of cytokines known for their anti-apoptotic effects. Purified CLL B-cells were cultured in the presence or absence of various soluble molecules and the leukemic cell response was assessed in terms of viability. Apoptotic cell death was detected by flow cytometry using annexinV and 7-amino-actinomycin. The survival of CLL B-cells in vitro was highly variable. When tested separately, cytokines (IL-2, -6, -10, -12, -15, -21, BAFF and APRIL) improved CLL B cell survival moderately; in combination, they significantly enhanced survival of these cells, even up to 7 days of culture. We also report that humoral factors from autologous serum are important for survival of these malignant cells. Our findings support the concept that the CLL microenvironment is critical and suggest that soluble factors may contribute directly to the prolonged survival of CLL B-cells. Therefore, the combination of cytokines we describe as providing strong resistance to apoptosis in vitro might be used to improve the treatment of CLL.

Research paper thumbnail of TLR9 ligand (CpG oligodeoxynucleotide) induces CLL B-cells to differentiate into CD20+ antibody-secreting cells

† Jean-Pierre Marolleau and Brigitte Gubler have contributed equally to this work.

Research paper thumbnail of Phorbol myristate acetate, but not CD40L, induces the differentiation of CLL B cells into Ab-secreting cells

In this study, we investigated the capacity of chronic lymphocytic leukemia (CLL) B cells to unde... more In this study, we investigated the capacity of chronic lymphocytic leukemia (CLL) B cells to undergo terminal differentiation into Ig-secreting plasma cells in T cell-independent and T cell-dependent responses. We used a two-step model involving stimulation with phorbol myristate acetate (PMA) and CD40L, together with cytokines (PMA/c and CD40L/c), for 7 days. We describe immunophenotypic modifications, changes in the levels of mRNA and protein for transcription factors and morphological and functional events occurring during the differentiation of CLL B cells into antibody-secreting cells (ASCs). The induction of differentiation differed significantly between the CD40L/c and PMA/c culture systems. The PMA/c culture system allowed CLL B cells to differentiate into IgM-secreting cells with an immunophenotype and molecular profile resembling those of preplasmablasts. By contrast, CD40L/c-stimulated cells had a phenotype and morphology similar to those of activated B cells and resembling those of the CLL B cells residing in the lymph node and bone marrow. These data suggest that the CLL B cells are not frozen permanently at a stage of differentiation and are able to differentiate into ASCs as appropriate stimulation are provided. The data presented here raise questions about the molecular processes and stimulation required for CLL B-cell differentiation and about the inability of CD40 ligand to induce differentiation of the CLL B cells.

Research paper thumbnail of Characterization of a new V gene replacement in the absence of activation-induced cytidine deaminase and its contribution to human B-cell receptor diversity.

In B cells, B-cell receptor (BCR) immunoglobulin revision is a common route for modifying unwante... more In B cells, B-cell receptor (BCR) immunoglobulin revision is a common route for modifying unwanted antibody specificities via a mechanism called VH replacement. This in vivo process, mostly affecting heavy-chain rearrangement, involves the replacement of all or part of a previously rearranged IGHV gene with another germline IGHV gene located upstream. Two different mechanisms of IGHV replacement have been reported: type 1, involving the recombination activating genes complex and requiring a framework region 3 internal recombination signal; and type 2, involving an unidentified mechanism different from that of type 1. In the case of light-chain loci, BCR immunoglobulin editing ensures that a second V-J rearrangement occurs. This helps to maintain tolerance, by generating a novel BCR with a new antigenic specificity. We report that human B cells can, surprisingly, undergo type 2 replacement associated with j light-chain rearrangements. The de novo IGKV-IGKJ products result from the partial replacement of a previously rearranged IGKV gene by a new germline IGKV gene, in-frame and without deletion or addition of nucleotides. There are wrcy/rgyw motifs at the 'IGKV donor-IGKV recipient chimera junction' as described for type 2 IGHV replacement, but activation-induced cytidine deaminase (AID) expression was not detected. This unusual mechanism of homologous recombination seems to be a variant of gene conversion-like recombination, which does not require AID. The recombination phenomenon described here provides new insight into immunoglobulin locus recombination and BCR immunoglobulin repertoire diversity.

Research paper thumbnail of A Combination of Cytokines Rescues Highly Purified Leukemic CLL B-Cells from Spontaneous Apoptosis In Vitro

B-chronic lymphocytic leukemia (B-CLL), the most common human leukemia, is characterized by predo... more B-chronic lymphocytic leukemia (B-CLL), the most common human leukemia, is characterized by predominantly nondividing malignant mature CD5+ B lymphocytes with an apoptosis defect. Various microenvironmental stimuli confer a growth advantage on these leukemic cells and extend their survival in vivo. Nevertheless, when cultured in vitro, CLL B-cells rapidly die from apoptosis. Certain cytokines may extend the survival capacity of CLL B-cells in vitro and individual antiapoptotic effects of several cytokines have been reported. The potential cumulative effect of such cytokines has not been studied. We therefore investigated the effects on CLL B-cells survival in vitro of humoral factors, polyclonal lymphocyte activators and a combination of cytokines known for their anti-apoptotic effects. Purified CLL B-cells were cultured in the presence or absence of various soluble molecules and the leukemic cell response was assessed in terms of viability. Apoptotic cell death was detected by flow cytometry using annexinV and 7-amino-actinomycin. The survival of CLL B-cells in vitro was highly variable. When tested separately, cytokines (IL-2, -6, -10, -12, -15, -21, BAFF and APRIL) improved CLL B cell survival moderately; in combination, they significantly enhanced survival of these cells, even up to 7 days of culture. We also report that humoral factors from autologous serum are important for survival of these malignant cells. Our findings support the concept that the CLL microenvironment is critical and suggest that soluble factors may contribute directly to the prolonged survival of CLL B-cells. Therefore, the combination of cytokines we describe as providing strong resistance to apoptosis in vitro might be used to improve the treatment of CLL.