Accessory cell function in immune responses in vivo: enhancing effect of radioresistant spleen cells on antibody response to SRBC in rats.

Spleen cells taken 4 days after lethal irradiation of Lewis rat were used as a source of radioresistant accessory cells. The transfer of 2 x 10(6) cells into syngeneic recipients significantly enhanced the antibody response to an immunogenic dose of SRBC, if given immediately prior to antigen. The enhancing effect was not observed if radioresistant cells were transferred 24 h or later after immunization. Elimination of adherent or phagocytic cells abolished the enhancing capacity of the radioresistant spleen cells. One hour pre-incubation in medium containing 0.4 mg/ml kappa carrageenan potentiated rather than inhibited the enhancing effect of radioresistant spleen cells. IgG PFC response appear to be more sensitive to the effect of the transferred spleen cells as compared with the direct (IgM) PFC response. It is concluded that activated splenic macrophages may enhance antibody response when transferred, at the time of immunization, into an immunocompetent host. Possible mechanisms of action are discussed.