Cells involved in the mitogen-induced helper function which facilitates the blastogenic response to Actinomyces viscosus.

Coculture of human peripheral blood lymphocyte suspensions, previously pulsed with either pokeweed mitogen (PWM) or an Actinomyces viscosus ultrasonicate supernatant fraction (AV), resulted in a blastogenic response that was greater than the sum of the responses of the two independently cultured lymphocyte suspensions. Selective cobalt-51 irradiation of the precultured lymphocytes prior to coculture revealed that PWM was inducing a helper activity which facilitated the blastogenic response to the poorly mitogenic AV. Subsequent experiments revealed that both Band T-enriched lymphocyte populations were capable of providing such help, however, the B-cell help appeared to require T-cell interaction. As few as one PWM-activated helper cell per 150 AV-pulsed cells was sufficient to provide measureable help. In the presence of PWM helper cells, both B and T cells gave strong blastogenic responses to AV fractions. Results of this study suggest that lymphocytes can respond to poorly mitogenic substances from bacteria if helper cell activity is provided by a second, unrelated lymphocyte stimulant.