The effect of indomethacin on burn-induced immunosuppression

Recent interest in the role of prostaglandin inhibitors as immunomodulators following major injury prompted us to study the effect of indomethacin on burn-induced immunosuppression in rats as measured by the delayed-type hypersensitivity (DTH) skin test response, ability to contain an intradermal bacterial challenge (10(8) Staphylococcus aureus 502A injected intradermally), and overall survival from spontaneous burn wound sepsis. Fifty male Sprague-Dawley rats sensitized to keyhole limpet hemocyanin (KLH) were subjected to a 30% full-thickness scald burn. Group 1 (n = 24) received indomethacin at 0.5 mg/kg intraperitoneally once daily with the first dose given immediately following the burn. Group 2 (n = 24) received vehicle only. Prostaglandin E2 measured by radioimmunoassay on day 17 was 2553 +/- 832 pcg/ml serum (+/- SEM) in the vehicle group and 1042 +/- 231 pcg/ml in the indomethacin group (P = 0.058, unpaired t test). Burn injury induced a decrease in the DTH response to KLH and an increase in the Staph lesion size (P less than 0.05) which was not corrected by indomethacin treatment. All animals developed spontaneous burn wound sepsis by day 14. Survival after 17 days in the indomethacin group was 100% compared to that of the vehicle group, 79%, P less than 0.05 (Fisher exact test). We conclude that despite unmeasurable corrections of the burn-induced suppression of the DTH response and local nonspecific bacterial defenses, low-dose indomethacin improves survival following burn sepsis.