Human T Lymphocyte Subpopulations: Studies of the Mechanism by Which T Cells Bearing Fc Receptors for IgG Suppress T-Dependent B Cell Differentiation Induced by Pokeweed Mitogen

Abstract

Abstract The mechanism by which human T lymphocytes bearing receptors for IgG (TG cells) suppress B cell differentiation promoted by pokeweed mitogen (PWM) and helper TM cells was studied. In this model system, autologous TG cells were shown to suppress via soluble factors released without detectable cell proliferation. In order to release these factors, TG cells needed to interact with PWM in addition to their reaction with IgG immune complexes during the isolation procedure. Suppression occurred only when TG cells were added early to mixtures of helper T and B cells cultured in the presence of PWM. B lymphocytes appeared to be resistant to suppression under a variety of experimental conditions. B cells “preactivated” by helper cells and PWM differentiated into plasma cells without any further help and were resistant to suppression by TG cells. B lymphocytes re-isolated from 2-day cultures containing TM cells, TG cells, and PWM retained their capacity to differentiate into plasma cells when cultured with helper T cells and PWM. B cell differentiation induced by helper supernatants was resistant to activated TG cells or their soluble factors. When TM cells were preincubated with suppressor supernatants, their ability to induce B cell differentiation was reduced; in contrast, similar pretreatment of B cells had no effect on their differentiation. These results suggest that TG cells can suppress the induction of polyclonal B cell differentiation by acting indirectly on helper TM cells.