The in vitro interleukin-1 (IL-1) and interleukin-2 (IL-2) production and IL-2 receptor (IL-2-R) expression by peripheral blood mononuclear (PBM) cells were examined in patients undergoing elective cholecystectomy. The IL-1 production by monocytes stimulated with a lipopolysaccharide (LPS) did not change on day +1 but increased by 57.5 % on day + 3 (p < 0.05) after surgery, and was normalized on days +5 and +7. The IL-1 production by PBMcells stimulated by LPS increased by 97.6% on day +1 (p < 0.05) and 109.5% on day + 3 (p < 0.05) after surgery, and became normalized on days +5 and +7. The IL-2 level in PBM cell supernatants stimulated with phytohemagglutinin (PHA) decreased by 45.2% on day +1 (p < 0.05), 33.3% on day + 3 (p < 0.05), 32.3% on day + 5 (p < 0.05) and returned to the preoperative values on day + 7. The IL-2-R expression on PHA-stimulated lymphocytes increased from 60.4 ± 4.8% preoperatively to 67.2 ± 1.9% on day +1 (p < 0.05) but was again within the preoperative values on days + 3, + 5 and + 7. In order to detect the described changes, stimulation with PHA had to be used. This indicates that simple surgical trauma produces subthreshold activation of blood immune cells. The cells enter the ‘response alert’ stage which can be measured after stimulation with lectins. A drop in the number of OKT+ cells but also insufficient production of IL-2 by OKT4+ cells for covering the requirements of activated cells may be responsible for the low levels of IL-2 detected after surgical t