Human B-cell activation in vitro. T cell-dependent pokeweed mitogen-induced differentiation of blood B lymphocytes.

Human blood lymphocytes were separated into T and non-T cells and cultured with pokeweed mitogen (PWM). It was found that in the absence of T cells no differentiation of B cells into immunoglobulin-containing blasts and plasma cells took place. Moreover, the cell yields and the rate of DNA synthesis and blast transformation were very low. The influence of T cells on PWM-induced B-lymphocyte differentiation was studied in mixtures of T/non-T cells at various ratios. Addition of even a few T lymphocytes caused a considerable stimulation of B cells by all parameters used. The responses of T/non-T mixtures of the original cellular composition were of the same order as those of cultures of unseparated cells. It is concluded that the differentiation of human blood B lymphocytes into cells actively synthesizing immunoglobulins, as induced by PWM, is strongly dependent upon the presence of T cells.