Different immunosuppressive effects of anti-red blood cell sera and their fractions obtained from various animal species.

Mouse spleen cells were cultured in the presence of anti-SRBC or anti-CRBC sera and SRBC or CRBC. There was no cross-reaction in the capacities of anti-SRBC and anti-CRBC sera to suppress IgM and IgG anti-haemolytic plaque formation in vitro. When CBA/H or DBA/2 mouse spleen cells were cultured in the presence of SRBC and CBA, DBA and C57 anti-SRBC sera (containing only IgG type haemolysins), respectively, there was a significant difference in immunosuppressive effects of these three kinds of sera, and the order of effectiveness was DBA > CBA > C57 molecules. When susceptibility of mouse spleen cells to immunosuppressive effects of each antiserum was tested, DBA cells were more sensitive to DBA anti-SRBC serum, and less to C57 antiserum than CBA cells were. CBA antiserum almost equally suppressed the plaque formation of CBA and DBA spleen cells. When CBA mouse spleen cells were cultured in the presence of SRBC and anti-SRBC IgG haemolysins raised in dogs and rabbits, rabbit IgG haemolysins were about eight times more effective than dog counterparts in their immuno-suppressive effects. Mouse IgM haemolysin molecules were not only ineffective but rather enhanced haemolytic plaque formation in the culture of mouse spleen cells. Haemagglutinin molecules obtained from mice and chickens were totally ineffective in the suppression of haemolytic plaque formation.