Human B cell precursors proliferate and express CD23 after CD40 ligation.

Abstract

SllmmaryThe CD40 surface membrane molecule plays an important role in the activation of mature human B cells, but its role in earlier stages orB lineage development is unknown. Here, we have investigated the effects of triggering the CD40 antigen on B cell precursors (BCP) by crosslinking with anti-CD40 antibody presented by Fc'/-receptor type II-transfected murine Ltk-cells (CD40 system). CD10 + surface immunoglobulin negative (slg-) BCP, freshly isolated from fetal bone marrow or precultured on stromal cells, proliferated in the CD40 system. This effect required the presence of IL-3, which acted as a specific cosignal among a panel of cytokines examined. The association of IL-10 and IL-7 potentiated the observed IL-3 and CD40-dependent BCP proliferation, demonstrating that IL-10 can act on early B lineage cells. CD40-dependent activation of fetal BCP did not favor maturation to slg + B cells, but resulted in the induction of high levels of surface membrane CD23. The emerging CD23 + BCP lacked slg and CD10, and represented an important proportion of the cycling cells in the CD40-dependent cultures. Taken together, our data demonstrate that stimulation of the CD40 antigen induces expression of the CD23 gene, and regulates cell proliferation during normal human B cell ontogeny.T he life history orB lymphocytes can be divided into two major steps. First, an antigen-independent process (B lymphopoiesis) permits constant generation of new immunocompetent surface (s)llgM + slgD + mature B cells in the bone marrow (for reviews see references 1 and 2). Then, mature B cells can be driven by antigens to proliferate and differentiate in secondary lymphoid organs (immunopoiesis) (for a review see reference 3). Both soluble cytokines and cell membrane-associated molecules regulate the various steps of B lymphocyte development. In this context, the CD40 B cell surface membrane molecule has recently been identified as playing a fundamental role in the process of immunopoiesis. Human CD40 is a 50-kD glycosylated phosphoprotein (4), that belongs to a new superfamily of receptors that includes the receptors for nerve growth factor and TNF (5, 6).Anti-CD40 antibody presented by Fc',/receptor type II (Fc'yRII) (CDw32)-transfected murine fibroblastic Ltkcells (CD40 system) induces strong and long-lasting B cell expansion in the presence of IL-4 (7, 8). The proliferation of anti-CD40-activated mature B cells is also enhanced by IL-10 (9). More strikingly, IL-10 allows CD40-activated B cells to produce large quantities of IgM, IgG, and IgA after their differentiation into plasma cells. Culturing CD40-activated naive slgD + slgM + B cells in the presence of IL-4 or IL-10 and TGF-~ induces the production of IgE or IgA, respectively, as a consequence of isotype switching (10-14).Recent studies have indicated that CD40 crosslinking represents the first step of the interaction between T and B cells. A ligand to CD40 has recently been identified and expressed from activated T cells, and CD40-Ig fusion proteins inhibit T cell-dependent B ce...

Does CD40 Ligation Induce B Cell Negative Selection?

“…Studies on the role of CD40 during early B cell ontogeny are scarce and in some cases conflicting. In one study (49), CD40 ligation on human fetal BM pro-B cells (CD34 ϩ /CD10 ϩ ) inhibited IL-7-induced proliferation in vitro, whereas in another, it induced surface Ig negative human B cell precursors to proliferate, acquire expression of CD23, and to become CD10 Ϫ /surface Ig Ϫ , in response to IL-3 and other cytokines (50). Although it was reported that CD40 expression both at the cell surface and mRNA in mice begins in pre-B cells, which are refractory to in vitro CD40-stimulation (51), in the current studies, CD40 expression was evident from the pro-B cell stage both in normal and in EP-CD154 tgM and was functional in vivo, as demonstrated by the CD154-CD40-dependent B cell depletion in EP-CD154.…”

The functional CD40 antigen of fibroblasts may contribute to the proliferation of rheumatoid synovium

“…A non-related antibody IgG1 was used for control at the same concentration. GM-CSF, granulocyte-macrophage colony-stimulating factor; TNF-, tumour necrosis factor-alpha; IFN-, interferon-gamma; bFGF, fibroblast growth factor b. and progenitor B cells [2,13]. Thus to reconstitute in vitro the CD40-CD40 L interaction occurring in vivo, synovial fibroblasts were cultured over a layer of irradiated CD40 L transfected L cells (L-CD40 L), and 3 H-TdT uptake was measured.…”

CD40 ligand upregulates expression of the IL-3 receptor and stimulates proliferation of B-lineage acute lymphoblastic leukemia cells in the presence of IL-3

“…[13][14][15] In these studies, IL-3 acted as a specific co-signal with anti-CD40 antibody for stimulating proliferation of normal BCP-cells, and proliferation was further enhanced by addition of IL-7 and IL-10. In the present study, addition of IL-7 to cultures with CD40L + IL-3 increased the proliferation and growth rate of BCP-ALL cells from some cases.…”

“…Furthermore, the stimulatory effect of both IL-3 and IL-7 on normal BCP-cells was remarkably increased following activation of CD40 by anti-CD40 antibody. Moreover, utilizing a co-culture system (CD40 system) in which BCP cells were stimulated by anti-CD40 monoclonal antibody immobilized on Fc␥-receptor-transfected murine Ltk− cells, Larson et al 14 and Saeland et al 15 found that normal human BCP cells were uniquely responsive to IL-3 in the presence of anti-CD40, although provision of either IL-3 or anti-CD40 alone had no effect on BCP cell proliferation. The CD40 antigen, a 50-kDa cell surface protein, is expressed on normal and neoplastic B cells, including BCP-ALL cells.…”