IgA-binding factors (IgA-BFs) prepared from human peripheral blood mononuclear cells selectively decrease the generation of cytoplasmic IgA-positive cells in peripheral blood mononuclear cell cultures stimulated by pokeweed mitogen or by Nocardia opaca delipidated cell mitogen. In N. opaca delipidated cell mitogen stimulated cultures, the suppressive effect of IgA-BFs was no longer demonstrable after removal of sheep erythrocyte rosetting T cells or after depletion of CD8+ cells, but it was not altered by depletion of CD4+ cells. In pokeweed mitogen stimulated cultures of T-depleted peripheral blood mononuclear cell suspensions, IgA-BFs were ineffective when irradiated (12 Gy) instead of control T cells were used for reconstitution. The data indicate that radiosensitive and CD8+ T cell subsets may be required for IgA-BFs to suppress the generation of IgA-containing B cells after polyclonal activation of human peripheral blood mononuclear cells.
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