Enhancement of anti-sheep erythrocyte plaque-forming cell levels by cimetidine in vivo

Abstract

Previous studies demonstrated an immunomodulatory role for cimetidine in contact sensitivity responses in vivo. The present experiments have examined the effects of cimetidine upon in vivo antibody production. When given intravenously, cimetidine treatment consistently resulted in enhanced numbers of IgM plaque-forming cells (PFC) following immunization with sheep erythrocytes. This enhancement was dependent upon both the dose and timing of cimetidine administration. In timing experiments, maximal enhancement of PFC levels was obtained when cimetidine was given at the time of or within three days following immunization. Treatment with cimetidine four days after immunization or one day before assay led to a slight decline in PFC level. In contrast, intraperitoneal treatment with cimetidine has little effect upon the anti-sheep erythrocyte PFC level regardless of dose or timing. Overall, these results indicate that cimetidine may be capable of modulating PFC development in vivo. This modulation, however, depends critically upon dose, timing, and route of cimetidine administration.