Monocyte function before and after surgical trauma.

The monocyte/macrophage plays a key role in the network of immune reactions. Dependent on activation, it is able to produce various cytokines which act on other cells of the immune system in the sense of upregulation or downregulation. In addition, it presents antigens by the HLA-DR molecule as an initial trigger of an antigen-specific T-cell response. Monocyte function is affected by surgical disease and further affected by surgical trauma. We found the monocyte to be activated in a subgroup of patients before the operation, related to an increased rate of postoperative septic complications. After the operation, plasma concentrations of IL-6 and IL-10 were increased indicating the activation of an immune response. After surgery HLA-DR expression decreased as well as LPS-stimulated TNFalpha and IL-6 production, the latter indicating a hyporesponsiveness of peripheral blood cells (presumably monocytes) to further stimulation. On the other hand, continuously high plasma concentrations of activation markers like neopterin and IL-6 in the postoperative course were associated with complications and poor outcome. In postoperative septic shock monocytes may be almost areactive towards natural stimuli like bacteria and endotoxin, since IL-6 and TNFalpha production decreased to very low amounts. Adequate pre- and postoperative monocyte function is related to an uneventful postoperative course after major surgical operations. Surgical trauma affects monocyte function rendering it less reactive, which is a potential risk factor for postoperative septic complications.