[Analysis of the specific feedback suppression mechanism in the primary anti-SRBC antibody responses].

The mechanism of the specific feed back suppression of the primary antibody responses induced by the preinjection of anti-SRBC antibodies was analysed. Preinjection of the rabbit anti-SRBC antibody suppressed the production of 7s antibodies in the primary anti-SRBC antibody responses in the WKA strain of rats. The 7s fraction but not Fab fragments of the rabbit antibody was effective in the induction of suppression. Therefore, the suppressive activity on the primary anti-SRBC antibody response is dependent on the Fc portion of the preinjected antibodies (7s). The suppressive effect induced by the preinjection of rabbit anti-SRBC antibodies was transferable passively to normal syngeneic rats with 19s antibodies of the serum, but not with spleen cells, of donor rats which had been preinjected with rabbit anti-SRBC antibodies. Moreover, production of anti-idiotypic antibodies (19s) was recognized in rats which had been preinjected with rabbit anti-SRBC antibodies. Consequently, it is strongly suggested in this experimental system that anti-idiotypic antibodies (19s) mediate the suppression of the 7s antibody production in the primary anti-SRBC antibody responses.