In vitro cytokine production and T-cell proliferation in patients undergoing cardiopulmonary by-pass.

Cardiac surgery, employing cardiopulmonary by-pass (CPB), has long been associated with a generalized immunosuppression. To further understand the complex physiological and immunological changes related to CPB, we decided to investigate whether CPB affects the immune response, with regard to T-cell activation and cytokine production. Using phytohaemagglutinin (PHA) as mitogen and peripheral blood mononuclear cells (PBMC) isolated from patients undergoing CPB, we investigated whether this procedure has any effect on interferon-gamma(IFN-gamma) and other cytokine production and/or PBMC proliferation. Comparisons were made between the responsiveness of PBMC obtained before, during and at the end of CPB. In all patients, CPB significantly reduces IFN-gamma and interleukin 2 (IL-2) production in response to PHA. On the other hand, tumour necrosis factor-alpha (TNF-alpha) production was also significantly diminished, while interleukin 6 (IL-6), interleukin 1 beta (IL-1 beta) and interleukin 8 (IL-8) release in response to PHA was not significantly affected. Reduced IFN-gamma, IL-2 and TNF-alpha production was associated with a significant decrease in PBMC proliferation. These results might be related to the mechanical damage on blood cells described during extracorporeal circulation procedures as well as the release of immunosuppressive factors during surgery. The immunosuppression observed during CPB may play an important role in the development of infectious complications after CPB.