Stimulation of immunoglobulin secretion in human B lymphocytes as a direct effect of high concentrations of IL 2.
In certain human IgM and IgG cell lines, immunoglobulin (Ig) secretion is highly stimulated by a B cell inducing factor (BIF) that is free of interleukin 2 (IL 2). BIF also induces Ig secretion in purified peripheral blood B cell populations that have been mitogenically stimulated by Staphylococcus aureus bacteria. Low concentrations of IL 2 (less than 20 U/ml) are not active in these systems. We now show that IL 2 at concentrations above 100 U/ml can induce Ig secretion in these blood B cells and B cell lines. Both conventional IL 2, purified from the human JURKAT and gibbon MLA-144 cell lines, and recombinant IL 2 are active. Very high concentrations approaching 10(4) U/ml are optimal for Ig secretion. Antibody to the T cell IL 2 receptor, anti-Tac, did not inhibit stimulation of the IgM cell line SKW6.4 by IL 2, and no Tac antigen was detected on the cells. The 9B11 monoclonal anti-IL 2 antibody that neutralizes T cell growth activity also abrogates stimulation of Ig secretion by conventional and recombinant IL 2 in the SKW6.4 cell line. However, the 1H11 monoclonal anti-(conventional thr3-glycosylated IL 2), which does not neutralize T cell growth activity, does inhibit induction of Ig secretion by the corresponding IL 2 in the B cell line. These results suggest that IL 2 stimulates B cells via a low-affinity interaction with a receptor different from the Tac receptor identified on T cells, and that the active site on the IL 2 molecule for B cells differs from that for T cell targets. If IL 2 promotes Ig secretion by binding with a low affinity to the B cell BIF receptor, IL 2 and BIF could be homologous proteins.
D000818:Animals; D000911:Antibodies, Monoclonal / Q000502:physiology; D000921:Antibody-Producing Cells / Q000378:metabolism*; D001402:B-Lymphocytes / Q000378:metabolism*; D001667:Binding, Competitive; D002460:Cell Line; D006801:Humans; D006922:Hylobates; D007136:Immunoglobulins / Q000096:biosynthesis*; D007376:Interleukin-2 / Q000378:metabolism / Q000502:physiology*; D011971:Receptors, Immunologic / Q000276:immunology; D015375:Receptors, Interleukin-2; D013209:Staphylococcal Vaccines / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D007136:Immunoglobulins; D007376:Interleukin-2; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2; D013209:Staphylococcal Vaccines