B-Cell Activation (original) (raw)
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IL7Responsive Pro-B Cells Stromal Cell-Independent Maturation of
The proliferation, survival, and differentiation of B cell progenitors in primary hematopoietic tissues depends on extracellular signals produced by stromal cells within the microenvironment. IL-7 is a stromal-derived growth factor that plays a crucial role in B lineage development. We have shown that in the presence of IL-7, pro-B cells proliferate and differentiate to a stage in which they are responsive to stromal cells and LPS, leading to terminally differentiated IgM-secreting plasma cells. In this report, we examine in detail the role of stromal cells in the transition from the IL-7-responsive pro-B cell stage to the mature LPS-responsive B cell stage. We demonstrate that this transition fails to occur, even in the presence of stromal cells and LPS, if constant exposure to IL-7 is maintained. The transition from the large pro-B cell stage to the small c ؉ pre-B cell stage occurs independent of stromal cells. Moreover, the "stromal cell-dependent" maturation that occurs subsequent to the expression of surface IgM leading to responsiveness to B cell mitogens can also be accomplished in the absence of stromal cells if pre-B cells are cultured in proximity to each other or at high cell concentrations. Together these results suggest that stromal cells mediate B cell differentiation by providing the necessary growth requirements (i.e., IL-7) to sustain the development of pre-B cells. The progeny of these pre-B cells can then differentiate through as yet unidentified homotypic interactions, leading to the production of LPS-responsive B cells.
Stromal cell-independent maturation of IL-7-responsive pro-B cells
Journal of immunology (Baltimore, Md. : 1950), 1998
The proliferation, survival, and differentiation of B cell progenitors in primary hematopoietic tissues depends on extracellular signals produced by stromal cells within the microenvironment. IL-7 is a stromal-derived growth factor that plays a crucial role in B lineage development. We have shown that in the presence of IL-7, pro-B cells proliferate and differentiate to a stage in which they are responsive to stromal cells and LPS, leading to terminally differentiated IgM-secreting plasma cells. In this report, we examine in detail the role of stromal cells in the transition from the IL-7-responsive pro-B cell stage to the mature LPS-responsive B cell stage. We demonstrate that this transition fails to occur, even in the presence of stromal cells and LPS, if constant exposure to IL-7 is maintained. The transition from the large pro-B cell stage to the small cmu+ pre-B cell stage occurs independent of stromal cells. Moreover, the "stromal cell-dependent" maturation that occ...
Immunity Mediated by B Cells and Antibodies
The production of antibodies is the sole function of the B-cell arm of the immune system. Antibodies are useful in the defense against any pathogen that is present in the extracellular spaces of the body's tissues. Some human pathogens, such as many species of bacteria, live and reproduce entirely within the extracellular spaces, whereas others, such as viruses, replicate inside cells but are carried through the extracellular spaces as they spread from one cell to the next. Antibodies secreted by plasma cells in secondary lymphoid tissues and bone marrow find their way into the fluids filling the extracellular spaces. Figure 7.1 Cross-linking of antigen receptors is the first step in B-cell activation. The B-cell receptors (BCR) on B cells are physically cross-linked by the repetitive epitopes of antigens (Ag) on the surface of a bacterial cell. The B-cell receptor on a mature, naive B cell is composed of surface IgM, which binds antigen, and associated Iga and Igb chains, which provide the signaling capacity. B-cell receptors are activated by cross-linking with antigens Ag BCR IgM Igα, Igβ B cell signals bacterial cell 183 Antibody production by B lymphocytes
In-vitro analyses of mechanisms of B-cell development
Seminars in Immunology, 1995
B-cell lymphopoiesis in vivo is vq complex due to the influences of cooperating cells, qtokines and other receptor-ligand interactions which appear to occur develojnnentally at daffment cellular stages. Therefore in-vitro models will help to unravel this complex situation. Here, we review our and others' work on in-vitro models of B-cell development. The role of stromal cells, cytokines, surrogate light chain and wducts of rearranged Ig-loci in the o!evela,bmentally different cellular stages will be discussed.
Blood, 1992
Newly formed B lymphocytes are a population of rapidly renewed cells in the bone marrow of mammals and their steady state production presumably depends on a cascade of regulatory cells and cytokines. Although considerable information has been forthcoming about the role of interleukin-7 (IL-7) in potentiating pre-B-cell proliferation, few studies have addressed the possibility that multiple cytokines are involved in the progression of early events in cellular differentiation and proliferation in this hematopoietic lineage. Our laboratory previously described pre-B-cell differentiation mediated by the bone marrow stromal cell line S17. In this study, we further delineate the role of stromal cells in differentiation and proliferation of pre-B cells. These experiments show that the stromal cell line S17 potentiates the proliferative effect of IL-7 on B-lineage cells and that this S17-derived potentiator can be replaced with recombinant kit-ligand (KL). Our results further show that pre-...