[The effect of cimetidine mainly increases CD4+ cells of peripheral blood T lymphocytes].

Cimetidine, one of the most popular histamine-2 receptor antagonists, has been reported to improve survival in gastrointestinal cancer patients and to activate cell-mediated immune response in surgical patients. NKT cells are a population of T cells that share characteristics with natural killer cells, and their main functions are production of immunoregulatory cytokines and cytolytic activities. In this study, we aimed to investigate the effect of cimetidine on the cell-mediated immunoresponse. Six healthy adult volunteers were given 800 mg of cimetidine per day orally, and their blood samples were taken prior to and at days 1, 3, 5, and 7 days post-administration of cimetidine. Leukocyte counts and differentials were obtained by the conventional hemogram, and the leukocyte subsets were analyzed by flow cytometry. Cimetidine administration caused leukocytosis, dependent on the increase of neutrophils, as well as of the CD3-positive T lymphocytes, and the subset of CD4-positive cells among them. On the other hand, the NK cell subpopulation was decreased, and the NKT cell subpopulation was not affected. The present results suggest that cimetidine is a modulator of the cellular immunity, and may be used as the activator of the tumor specific immunoresponse.