INVITRO GENERATION OF ANTIGEN-SPECIFIC SUPPRESSOR T-CELL ACTIVITY - CULTURE CONDITIONS FOR ABROGATING THE INDUCTION OF NONSPECIFIC SUPPRESSOR T-CELLS

When murine lymphocytes were cultured in RPMI-1640 medium containing fetal calf serum (FCS) for more than 3 d without added antigens, suppressor T cells (Ts) that suppressed in vitro antibody responses to sheep erythrocytes, dinitrophenyl-Ficoll and trinitrophenyl (TNP)-lipopolysaccharide nonspecifically were induced spontaneously. Thus, we failed to detect the activities of antigen-specific Ts that are generated by priming the lymphocytes in vitro with a specific antigen under these experimental conditions. To avoid the induction of nonspecific Ts, we examined various culture conditions and found that nonspecific Ts were not induced only when a specific lot of FCS (NSF 107) was used. When the lymphocytes were cultured with Keyhold limpet hemocyanin (KLH) in NSF 107-containing culture medium, we could detect KLH-specific Ts activity that specifically suppressed the secondary response to TNP-KLH without the interference of nonspecific Ts. Similar experiments were successful if we used FCS that was previously treated at 70.degree. C for 10 min instead of native ones. Immunoelectrophoretic analysis revealed that the level of a component belonging to .alpha.-globulin fraction was markedly low in NSF 107 as compared with all other lots of FCS that could induce nonspecific Ts. Removal of this component from FCS by an immunoadsorbent resulted in the loss of the capacity to induce nonspecific Ts. On the other hand, when the lymphocytes were cultured in the presence of varying amounts of this component, nonspecific Ts were generated in a dose-dependent manner.