Functional analysis of two human T-cell subpopulations: help and suppression of B-cell responses by T cells bearing receptors for IgM or IgG.

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Abstract
Subpopulations of thymus-derived (T) lymphocytes bearing receptors for Ig[immunoglobulin]M or IgG molecules were isolated from human peripheral blood. Those with receptors for IgM (T.M) provided help in a cell dose-dependent fashion for the pokeweed mitogen-induced differentiation of B [bone marrow-derived] lymphocytes in vitro, whereas cells with receptors for IgG (T.G) did not. T.G cells efficiently suppressed the differentiation and proliferation of B cells in the pokeweed system in the presence of helper T.M cells. This suppressive activity of T.G cells required prior interaction of the T.G cells with immune complexes. The helper activity of T.M cells was relatively radioresistant while the suppressor activity of T.G cells was radiosensitive. Helper and suppressor functions of human T lymphocytes in this model system are apparently mediated by different subpopulations of T cells which can be distinguished by their ability to bind IgM or IgG immune complexes, respectively.