MLC-inhibiting serum in mice after transfusion with 3 M KCl-extracted soluble antigen

Balb/c (H-2d) mice were transfused weekly with 3 M KCl-extracted soluble antigen prepared from splenocytes of C3H/HeJ (C3H)(H-3k) mice. One week after each transfusion, spleen and serum samples were collected from transfused mice and pooled. The serum was absorbed with erythrocytes and spleen cells from C3H mice and heat inactivated. Spleen cells from transfused mice were tested for proliferative responses in mixed lymphocyte culture (MLC) against stimulator cells from the antigen donor C3H or from third party SJL (H-2s) mice. The proliferative responses of lymphocytes from soluble-antigen-transfused Balb/c mice to stimulator cells from C3H and SJL mice were not suppressed. Furthermore, suppressor cells could not be demonstrated in spleens of transfused mice in in vitro coculture experiments. The MLC inhibition test was utilized to investigate the presence of MLC-inhibiting serum from transfused mice. The results demonstrate that serum capable of inhibiting responses of Balb/c mice were induced after three weekly injections of soluble antigen and that this inhibition in MLC was specific for the stimulator cells from the antigen donor C3H mice. These findings differ from our studies using whole blood transfusions where (1) MLC inhibiting antibodies developed in Balb/c mice after only one transfusion of C3H whole blood, and (2) serum from blood transfused mice achieve greater inhibition than soluble-antigen-induced serum. These results suggest that although soluble antigen is capable of inducing MLC inhibiting serum, the kinetics of this induction may be different from transfusion with whole blood.