Natural killer cell activity after open-heart surgery.

We studied the effects of elective open-heart surgery with cardiopulmonary bypass on peripheral blood natural killer (NK) cell activity in 12 patients with heart disease. Separated mononuclear cells from patients and control cells taken from healthy volunteers were incubated in microtiter plates for 24 h with 3H-thymidine-labelled K 562 cells as target cells. In this test system, higher counts per minute (cpm) values represent a greater number of surviving target cells and thus weaker NK activity. Results of cultures prepared from blood samples taken preoperatively were compared with those taken 2, 7 and 14 days postoperatively. NK cell activity was depressed (P less than 0.01) for 2 days after surgery. NK cell activity in the control samples did not change significantly. The results show an impairment of NK cell activity immediately after open-heart surgery.