Early decrease in surface expression of HLA-DQ predicts the development ofinfection in trauma patients

The behaviour of human leucocyte antigen-DR (HLA-DR) following injury has b een extensively studied. However, the behaviour of other class II antigens following trauma has not been characterized as well, despite evidence that HLA-DQ genotype influences the response to several bacterial antigens. Our study attempts to characterize and analyse the behaviour of HLA-DQ after tr auma in patients with and without infection. Twenty-five patients were stud ied following major injury. Fifteen of the 25 patients developed infection (men = 11, women = 4); 10 patients developed no infection (men = 9, women = 1). The mean age was 34 +/- 12 years for patients with no infection and 52 +/- 20 years for those with infection. Monocyte HLA-DQ surface expression was determined using FITC-labelled antibodies and flow cytometry. Expressio n was compared with a control population of 11 healthy volunteers. The perc entage of monocytes expressing HLA-DQ following trauma was reduced in patie nts with infection and in those without infection, but returned to normal ( days 8-14) only in those patients who did not develop infection. Monocyte H LA-DQ mean channel fluorescence was reduced on day 1, but quickly returned to normal in those patients who subsequently developed infection. Stimulate d with lipopolysaccharide, the initial samples of 13 patients who developed infection showed that surface expression on these monocytes could be eleva ted into the normal range. We conclude that HLA-DQ is an additional early m arker of outcome that may not function merely as an immune suppressor. The maintained ability of HLA-DQ to present self-antigens may be important in t he initial stages of the host response to injury.