The effects of thiol moiety of levamisole on both cellular and humoral immunity during the early response to a hapten-carrier complex.

Cell-mediated reactions to the carrier and antibody-mediated reactions to the hapten were studied in guinea-pigs treated with a single i.v. injection of the thiol moiety of levamisole (DTC), before or after immunization with a hapten-carrier complex. The results show that a heavy dose of DTC induced delayed hypersensitivity reactions to the carrier and decreased antibody synthesis to the hapten. On the other hand, with a small dose of DTC no delayed hypersensitivity could be induced, but antibody synthesis to the hapten was depressed or enhanced, depending upon whether the injection was done before or after immunization. The mechanisms whereby DTC modulated the immune response are discussed.