Effects of hydrocortisone and adrenaline on natural killer cell activity.

We have studied the effects of hydrocortisone and adrenaline on natural killer (NK) cell activity and on the distribution of circulating lymphocyte subpopulations in 30 patients undergoing elective partial laminectomy under general anaesthesia. The patients were allocated to receive adrenaline (group 1, n = 11), hydrocortisone and adrenaline (group 2, n = 11) or neither hydrocortisone nor adrenaline (group 3, n = 8). Group 1 and group 2 patients received local adrenaline infiltration during operation to reduce bleeding. The mean dose of adrenaline administered was 2.1 (SD 0.2) microgram kg-1. Group 2 received hydrocortisone 10 mg kg-1 i.v. after premedication. In groups 1 and 2, adrenaline produced an instantaneous increase in NK cell activity accompanied by a selective increase in circulating NK cells. The measurements returned to pre-infiltration levels within 120 min of administration of adrenaline. The effect of adrenaline in causing increased NK cell activity was not blocked by pre-administration of hydrocortisone. There was a significant decrease in the ratio of T-helper/inducer cells (CD4) to T-suppressor/cytotoxic cells (CD8) in all patients after induction of anaesthesia. In groups 1 and 3, the CD4/CD8 of anaesthesia. In groups 1 and 3, the CD4/CD8 cell ratio did not change significantly during operation. However, compared with groups 1 and 3, group 2 showed a significantly reduced CD4/CD8 cell ratio during operation. Therefore, these results suggest that even in cases of such severe stress that the immune response was depressed by increased serum cortisol concentrations, adrenaline-induced NK cell activity enhancement was preserved.