Interleukin-2 is required for the induction of erythrocyte--specific antibody responses in human lymphocyte cultures.

The involvement of interleukin-2 (IL-2) in the generation of human antibody responses was studied using the pokeweed mitogen (PWM)-induced sheep erythrocyte-specific plaque-forming cell (SE-PFC) response of cultured tonsilar lymphocytes. IL-2-containing supernatants from phytohemagglutinin-stimulated human spleen or tonsil cells or the cloned human T cell line JURKAT were capable of replacing the requirement for PWM in the generation of SE-PFC and resulted in a more prolonged response than that observed with PWM. This effect of IL-2-containing medium was dependent on the presence of SE-derived antigens and was not due to the induction of polyclonal antibody synthesis. When purified by gel filtration the SE-PFC-inducing activity co-eluted with IL-2 with an apparent molecular weight of approximately 15,000 (range, 8,000-20,000). Selective removal of IL-2 from crude or partially purified IL-2 preparations by extensive adsorption with activated murine thymocytes or an IL-2-dependent T cell line completely eliminated SE-PFC-inducing activity, indicating that IL-2 itself was necessary for the effect. The question of whether or not this effect was mediated through T cells is discussed.