Functionally distinct human T-lymphocyte clones sharing potent suppressive activity on immunoglobulin secretion.

T-lymphocyte clones derived from populations sensitized to alloantigens in vitro were tested for their regulatory effects on pokeweed mitogen-stimulated immunoglobulin (Ig) secretion. Clones with natural killer (NK)-like cytotoxicity and/or suppressive activity for lymphoproliferative (LP) responses potently inhibited Ig secretion. Moreover, certain alloproliferative T4+ interleukin-2 (IL-2)-secreting 'helper' clones shared this strong suppressive activity on Ig secretion. The remaining clones enhanced, rather than suppressed, Ig production. Inhibition by all types of suppressive clones appeared not to be restricted by MHC products, since allogeneic HLA-mismatched donors were suppressed as efficiently as the autologous donor. Suppression was radioresistant, and was apparently not caused by absorption of IL-2, or cytotoxicity of the clones. Suppression was still detectable at plateau levels when cloned cells were added as late as 96 hr after the initiation of the cultures, suggesting an inhibitory mechanism divorced from early B-cell activation events. Thus, T-lymphocyte clones with distinct different functional activities share similar profound suppressive effects on Ig secretion in vitro.