Abstract: Conditioned immunosupression of rabbit anti rat lymphocyte serum (ALS), a biological immunosuppressant, was assessed in the experiment using a two bottle preference drinking procedure. The data showed that ovalbumine (OVA) immunized rats conditioned by pairing a novel saccharin solution (CS) with an ip injection of ALS (UCS) showed conditioned immunosuppression in vitro PWM induced spleen proliferation and in total anti OVA Ig antibody production as well as in anti OVA containing cells in spleen, but did not show conditioned taste aversion. These results suggested that there was no association between the conditioned taste aversion and the conditioned immunosuppressive responses and that the conditioned immunosuppression was not the concomitant of behavioral suppression, but the result of the CS UCS associative learning mediated by the central nervous system.

Key words: anti rat lymphocyte serum, conditioned taste aversion, rat, conditioned immunosuppression