T cell-derived B cell growth and differentiation factors.
In the last few years it has been demonstrated that clonal expansion of B lymphocytes and their differentiation into antibody-producing cells are regulated by a complex series of soluble products released by T cells. The application of cloning and recombinant DNA techniques has made it possible to obtain most of these molecules in a purified form and, therefore, to study in more detail their functional properties. To date, three distinct T cell-derived B cell growth factors (BCGFs) and/or B cell differentiation factors (BCDFs), i.e., IL-2, IL-4 and IL-5, have been reported for mouse B cells. Likewise, at least five distinct molecules showing BCGF and/or BCDF activity (IL-2, IFN-gamma, IL-4, the 12 kD-BCGF and BSF-2) for human B cells have been identified. Human T cell-derived lymphokines active on B cells are functionally similar but not identical to murine lymphokines. Most T cell-derived lymphokines can exert their activity on the same B cells in different stages of activation and evoke different responses. In addition, some of them are not specific for B cells, but act as competence factors or competence cofactors for different hemopoietic cell lines. Finally, convincing evidence is accumulating to suggest that both activated and resting B cells may have receptors for BCGFs and BCDFs. This makes it clear why although the goal of a directed immune response is to generate antigen-specific antibodies, a large part of this response can actually be polyclonal and nonspecific.
Romagnani
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Cattedra di Patologia Speciale Medica e Metodologia Clinica, Università degli Studi di Firenze.
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D006801:Humans; D007376:Interleukin-2 / Q000276:immunology; D015847:Interleukin-4; D007378:Interleukins / Q000276:immunology*; D008213:Lymphocyte Activation; D013601:T-Lymphocytes / Q000276:immunology*
D007376:Interleukin-2; D007378:Interleukins; D015847:Interleukin-4