Lymphokine-induced suppressor B cells.

Accessory activity required for in vitro antibody production by murine B cells is mediated by macrophage- and helper T-cell-derived lymphokines (IL-1 and TRF, respectively). The synergistic helper activity that occurs when TRF is added early rather than late in the response cannot be attributed to the initiation. We found that the suboptimal helper activity which occurs when TRF is added early rather than late in the response cannot be attributed to the inactivation of the mediator, but results instead from the generation of helper factor-induced suppressor cells. Serological examination revealed that these suppressor cells exhibit the cell surface phenotype (Thy 1-, Ia+, IgG+, IgD+) of a B cell. In an attempt to attribute the generation of suppressor B cells to a distinct T-cell product we examined two T-cell mediators believed to be present in TRF, namely IL-2 and a second factor recently introduced as (DL) TRF. Our results point to a dichotomy of the induction pathways involved in the generation of antibody-forming cells and the activation of suppressor B cells, the former involving IL-1 and IL-2, and the latter involving IL-1 and (DL) TRF.