Interleukin-10. A role in the development of postoperative immunosuppression.

Background: The cause of diminished monocyte major histocompatibility complex class II antigen expression after surgery or trauma is unclear. Interleukin-10 (IL-10) regulates inflammatory cytokine production and major histocompatibility complex class II (HLA-DR) expression in vitro.

Objectives: To quantify in vivo IL-10 messenger RNA (mRNA) and protein and monocyte HLA-DR expression after major surgery and to investigate the effects of IL-10 neutralizing blockade on monocyte HLA-DR expression in vitro.

Design: Inception cohort study of 48 surgical patients from preoperative status to postoperative day 7 and 9 healthy volunteers (controls).

Setting: Large teaching hospital, Northern England.

Patients: Monocyte HLA-DR and cytokine mRNA expression was determined in 32 of 48 consecutive patients undergoing elective major resectional surgery. Mononuclear cells for in vitro studies and serum samples for IL-10 measurement were obtained from the remaining 16 patients.

Main Outcome Measures: Monocyte HLA-DR expression determined by flow cytometry, IL-10, and tumor necrosis factor mRNA in peripheral blood mononuclear cells assayed by multiplex reverse transcriptase polymerase chain reaction, and serum IL-10 determined by enzyme-linked immunosorbent assay.

Results: Monocyte HLA-DR expression (in mean channel fluorescence units [MCF]) was significantly reduced 24 hours after surgery (MCF [+/- SEM], 32.6 +/- 2.3 vs 16.3 +/- 1.2; P < .001) and remained low during the first postoperative week. A relative increase in IL-10 to G3PDH mRNA ratio (mean [+/- SEM], 0.95 +/- 0.08 vs 0.59 +/- 0.06; P < .01) and serum IL-10 (mean [+/- SEM], 18.1 +/- 4.1 vs 5.4 +/- 0.8 pg/mL; P < .01) was noted on the first postoperative day. A significant correlation existed between HLA-DR antigen expression and the presence of IL-10 mRNA transcript on the first postoperative day (P < .01). Lipopolysaccharide-induced up-regulation of monocyte HLA-DR expression was significantly impaired on the first postoperative day (mean [+/- SEM], 151% +/- 24.4% vs 60% +/- 10.1%; P < .01), but this was partially reversed by IL-10 neutralizing antibody (mean [+/- SEM], 60% +/- 10.1% vs 115% +/- 11.6%; P < .01).

Conclusions: Interleukin-10 gene expression correlates with the fall in monocyte HLA-DR antigen expression in patients undergoing major abdominal surgery and may account for the immunosuppression associated with surgical injury.