The effect of cimetidine on antibody synthesis in vitro and in vivo

The effects of the H₂-receptor antagonist cimetidine on the antibody response of murine spleen cells to sheep red blood cells (SRBC) has been examined in vitro and in vivo. Studies failed to demonstrate any detectable effect of the drug in vitro over a wide range of concentrations (10^-12 to 10^-4M). In vivo, cimetidine stimulated IgM but not IgG responses. This effect was more marked on the secondary rather than the primary response. Low doses of cimetidine (0.5–10 mg/kg) enhanced the secondary IgM response better than higher concentrations (50–100 mg/kg).