Suppression of polyclonal B cell activation by IgG-binding factors. Requirement for T cells

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Abstract
IgG‐binding factors (IgG‐BF) prepared from cell‐free supernatant of human peripheral blood mononuclear cells interfere with the polyclonal activation of peripheral B cells by decreasing the numbers of IgG‐containing cells and Ig plaque‐ forming cells. Using Nocardia opaca delipidated cell mitogen (NDCM), a T helper cell‐independent polyclonal B cell activator, it was found that the suppressive effect of IgG‐BF was no longer demonstrable after removal of T cells. In pokeweed mitogen‐stimulated cultures, the suppression by IgG‐BF required the presence of radiosensitive T cells. Selective depletion of OKT4+ or OKT8+ subsets in NDCM‐stimulated cultures showed that IgG‐BF required the presence of OKT4+ lymphocytes to induce suppression. It is concluded that the effect of human IgG‐BF was mediated by one or several subsets of T cells.