Association between Reduced Human Leukocyte Antigen (HLA)-DR Expression on Blood Monocytes and Increased Plasma Level of Interleukin-10 in Patients with Severe Burns

Severe thermal injury causes an immune dysfunction which includes a decrease of monocyte human leukocyte antigen DR (HLA-DR) expression. Interleukin-10 exerts a negative influence on this parameter in vitro. In this study we determined the prognostic value of reduced monocyte HLA-DR expression with regard to infectious complications, and the in vivo association between monocyte HLA-DR and plasma interleukin-10 concentration. Both quantities were measured serially in 19 patients with severe burns. HLA-DR expression was determined by direct immunofluorescence on a flow cytometer, and interleukin-10 was measured by ELISA. After burn trauma the percentage of HLA-DR expressing monocytes fell markedly (median: 53% at day 2, 36% at day 4, 31% at day 7, 28% at day 9, 35% at day 12, and 42% at day 14; compared to 93% for healthy volunteers). Moreover, patients who became septic showed lower monocyte HLA-DR expression than non-septic patients; the differences were significant at day 2 (p < 0.01) and day 7 (p < 0.05). Plasma concentrations of interleukin-10 increased after thermal injury (median: 40 ng/l at day 2, 43 ng/l at day 4, 77 ng/l at day 7, 120 ng/l at day 9, 63 ng/l at day 12, and 82 ng/l at day 14). Individual HLA-DR expression and interleukin-10 concentration were negatively correlated, the association reaching statistical significance at day 4 (p=0.006) and day 7 (p=0.031). Thus, after severe burn injury monocyte HLA-DR expression has prognostic value and is negatively associated with interleukin-10 plasma concentration.