Effect of ranitidine on postoperative suppression of natural killer cell activity and delayed hypersensitivity

In a randomized study of patients undergoing major elective abdominal surgery, 12 received i.v. ranitidine (50 mg every 6 hours for 72 hours from the skin incision) and 12 had no ranitidine. Cell-mediated immunity was assessed pre- and postoperatively by skin testing with seven common delayed type hypersensitivity (DTH) antigens, and blood drawn immediately before and 24 hours after skin incision was analyzed for spontaneous and in vitro stimulated (IL-2, IFN-alpha or indomethacin) natural killer (NK) cell activity and PHA and PPD-stimulated lymphocyte proliferation. Lymphocyte subsets (helper/inducer-T cells, suppressor/cytotoxic-T cells, Pan-T cells and NK-cells) were counted by flow-cytometry. Perioperative ranitidine diminished the expected postoperative reduction in DTH responses (p less than 0.0001), as well as in spontaneous NK-cell activity (p less than 0.03) and in vitro IL-2 stimulated NK-cell activity (p less than 0.02). Postoperative decrease in helper/inducer-T cell numbers was not significantly lessened (p = 0.07), and ranitidine did not influence the levels of suppressor-T cells. PHA and PPD responses in peripheral blood mononuclear cells were unaltered. The results may suggest potential benefit from ranitidine as regards postoperative infectious complications and recurrence of malignancy.