Immunological status of patients subjected to cardiac surgery: serum levels of interleukin 6 and tumor necrosis factor alpha and the ability of peripheral blood mononuclear cells to proliferate and produce these cytokines in vitro

Abstract

The aim of this study was to monitor plasma interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) levels in patients subjected to cardiac surgery under general anesthesia. In addition, proliferation of peripheral blood mononuclear cells (PBMC) to phytohemagglutinin (PHA) and the ability of these cells to secrete lipopolysaccharide-induced IL-6 and TNF-alpha during the observation period was investigated. IL-6 and TNF-alpha levels were measured using bioassays. We found that despite high variability in the postoperative response of the patients, characteristic kinetics in the appearance of the cytokines in plasma could be demonstrated. Most significant phenomenon was an increase of IL-6 level 1 day after operation associated with an inhibition of TNF-alpha concentration. Relatively high, preoperative concentrations of these cytokines were probably elicited by stress. Control, healthy donors, did not exhibit measurable levels of these cytokines. In terms of proliferative response of PBMC to PHA and of cytokine production in vitro, the patients could be classified into low and high responding. The proliferative response of PBMC from low responders was progressively increasing and the response of high responders did not exhibit meaningful changes throughout the observation period. PBMC from low producers of IL-6 showed also an increased ability to secrete this cytokine during the monitoring time while the cells from high producers yielded less IL-6 on the last day of the follow up. Regarding TNF-alpha production, PBMC from low responders reacted strongly by secretion of this cytokine on day 1 after surgery in contrast to high responders whose cells yielded less TNF-alpha after surgery. In majority of cases TNF-alpha production had a tendency to diminish on the last day of observation. We conclude that the changes in cytokine levels as well as an altered reactivity of PBMC in vitro reflect the immune response to the postoperative trauma and are desirable for a normal course of the immune response and wound healing.