Abstract
The humoral immune response against a thymus-dependent antigen, sheep red blood cells (SRBC), was suppressed in mice in-jected with levamisole i.v. at a few days before challenge with the antigen. The suppressive effect of levamisole was modified by an antigen dose, a drug dose and a timing of drug administration. The suppression of plaque-forming cell (PFC) response was observed at an optimal antigen dose of 2×108 SRBC while the augmentation was observed at a suboptimal antigen dose of 2×107 SRBC, at the same dose of the drug. However, no suppressive effect on serum antibody level was found throughout the experiments. Levamisole also shifted the peak of IgM-PFC earlier and the peak of IgG-PFC later respectively than in normal responses. Transfer of spleen cells from levamisole-treated donors to untreated recipients resulted in antigen specific suppression in the recipient immune response.
These results suggest that, for the most part, an induction of antigen-specific suppressor cells in the spleen accounts for the suppression of humoral immunity by levamisole.
