In spite of proven immunoregulatory effects in vitro of recombinant human interferon-gamma (rhIFN-gamma) in trauma, clinical trials remain inconclusive in such patients. To investigate the in vivo effect of rhIFN-gamma perioperatively in surgical patients we did a pilot study in 46 patients termed anergic by negative delayed-type hypersensitivity (DTH) skin test, who were undergoing major surgery (22 women and 24 men). They received 100 micrograms of rhIFN-gamma subcutaneously (treated [T]; n = 24) in a double-blind, placebo- (control [C]; n = 22) controlled manner on preoperative days -7, -5, and -3. Whole-blood cultures were stimulated on days -7, -1, 4, 7, and 10 for 12 h with or without LPS (1 microgram/mL). Mild side effects such as fever, headache, or chills were observed in 7/24 patients. No major complications occurred and no significant effect of rhIFN-gamma on HLA-DR, IL-1, and IL-8 was demonstrated. PGE2, TNF-alpha and IL-6 levels were elevated perioperatively in T. versus C. Neopterin, a metabolite of activated monocytes and macrophages, was significantly activated on days -1 (C: 7.6 +/- 1.2 versus T: 20.5 +/- 2.4 nmol/mL; P < 0.001), day 1 (C: 8.3 +/- 1.4 nmol/mL versus T: 24.9 +/- 2.8 nmol/mL; P < 0.001), and day 4 (C: 9.5 +/- 1.1 nmol/mL versus T: 16.0 +/- 1.8 nmol/mL; P < 0.05). Due to the overall lack of infectious complications during the investigation, no clinical effect was shown for rhIFN-gamma treatment. DTH skin testing failed to detect high-risk individuals in the patient population studied. In conclusion, we demonstrated in our pilot study that pre-operative immunomodulation with rhIFN-gamma in surgical anergic patients did not show severe side effects and modulated in vitro immunoresponse. A larger clinical trial in better-defined high-risk patients may show whether a reduction of infectious complications can be achieved.