Increased secretion of hyperimmune antibodies following lipopolysaccharide stimulation of CD40-activated human B cells in vitro.
Human B cells can be cultured ex vivo for a few weeks, following stimulation of the CD40 cell surface molecule in the presence of recombinant cytokines such as interleukin-4 (IL-4). However, attempts to produce polyclonal antigen-specific human antibodies by in vitro culture of human B cells obtained from immunized donors have not been successful. It has been shown in mice that lipopolysaccharide (LPS) is a potent mitogen for B cells and plays an important role in the generation of antigen-specific antibody responses. Although it has long been believed that LPS has no direct effect on human B cells, recent data indicating that IL-4-activated human B cells are induced to express Toll-like receptor-4, the main LPS receptor, prompted us to study the effects of LPS on the proliferation and antibody secretion of human B cells. Our results showed that LPS caused a reduction in the expansion of CD40-activated human B cells, accompanied by an increase in antigen-specific antibody secretion. This result suggested that some, but not all, B cells were able to differentiate into antibody-secreting cells in response to LPS. This increased differentiation could be explained by the observation that LPS-stimulated human B cells were induced to secrete higher amounts of IL-6, a pleiotropic cytokine well-known for its B-cell differentiation activity. In vivo, the effect of LPS on cytokine secretion by B cells may not only enhance B-cell differentiation but also help to sustain a local ongoing immune response to invading Gram-negative bacteria, until all pathogens have been cleared from the organism.
Dumont
Nellie
N
Department of Research and Development, Héma-Québec, QC, Canada.
Aubin
Eric
E
Proulx
Dominic P
DP
Lemieux
Réal
R
Bazin
Renée
R
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D019013:CD40 Antigens / Q000276:immunology*; D002460:Cell Line; D049109:Cell Proliferation; D002478:Cells, Cultured; D018985:Epitopes, B-Lymphocyte / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000096:biosynthesis; D007075:Immunoglobulin M / Q000096:biosynthesis; D016753:Interleukin-10 / Q000096:biosynthesis; D015847:Interleukin-4 / Q000276:immunology; D015850:Interleukin-6 / Q000096:biosynthesis; D008070:Lipopolysaccharides / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology*; D051379:Mice; D053668:Syndecan-1 / Q000032:analysis
D019013:CD40 Antigens; D018985:Epitopes, B-Lymphocyte; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D015850:Interleukin-6; D008070:Lipopolysaccharides; C508241:SDC1 protein, human; D053668:Syndecan-1; D016753:Interleukin-10; D015847:Interleukin-4
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