Conditions for induction of specific and polyclonal antibody production by Cowan 1 bacteria and by pokeweed mitogen.

Cowan 1 bacteria and pokeweed mitogen (PWM) were used to induce the formation of direct plaque-forming cells (PFC) against sheep erythrocytes (SRBC) by human peripheral blood lymphocytes in vitro. It was necessary to absorb the serum supplement with SRBC before culture to obtain anti-SRBC PFC. Alternatively, sheep serum could be added to the cultures. The PFC response was specific, and the response was equally high in cultures with a mixture of absorbed and non-absorbed serum as in cultures with absorbed serum only. Cowan 1 and PWM could also induce synthesis and secretion of both IgM and IgG polyclonal antibodies. Absorption with SRBC or addition of sheep serum had no effect on this synthesis. Thus it seems likely that the induction of anti-SRBC PFC by Cowan 1 or PWM needs the presence of SRBC antigen and is the result of a synergism between mitogen and antigen. Consequently, the anti-SRBC PFC response obtained after stimulation with Cowan 1 or PWM in SRBC-absorbed serum does not reflect a true polyclonal antibody response.