Monocyte activation after open and laparoscopic surgery

The level of expression of major histocompatibility complex class II antigens, human leucocyte antigen (HLA)-DR, on monocytes correlates with the development of sepsis after surgery or trauma. Normally interferon (IFN) gamma can increase monocyte HLA-DR expression and thus may be a potential biological prophylactic antisepsis agent in patients suffering from accidental or surgical trauma. The purpose of this study was to determine the capacity of monocytes to respond to IFN-gamma after conventional open surgery and laparoscopic surgery of similar magnitude.

A whole blood flow cytometric assay was used to measure monocyte HLA-DR antigen expression before and after monocyte activation with either IFN-gamma or bacterial lipopolysaccharide (LPS). Blood was obtained before operation and on postoperative day 1 from 43 patients undergoing conventional open surgery and from 15 undergoing laparoscopic surgery of similar magnitude.

Whole blood monocyte HLA-DR expression fell significantly after both conventional open and laparoscopic surgery. IFN-gamma caused monocyte HLA-DR expression to rise by a median (interquartile range) of 43 (26-60) per cent and 63 (10-124) per cent before operation in the open and laparoscopic groups respectively. However, after operation the corresponding values were 20 (6-41) per cent and 26 (9-74) per cent (P < 0.003 in all cases). Identical findings but of greater magnitude were observed with LPS stimulation before and after operation in the two surgical groups.

Monocyte HLA-DR expression is diminished by surgical operations and is relatively refractory to further stimulation by IFN-gamma or LPS after surgery. Laparoscopic surgery is as suppressive as conventional surgery in this regard. The resistance of postoperative monocytes to further activation by IFN-gamma suggests that this agent may be ineffective as a biological response modifier after major surgery or trauma.