Up-regulation of cell surface Toll-like receptors on circulating γδ T-cells following burn injury

Burn injury is associated with profound inflammation and activation of the innate immune system involving gamma delta T-cells. Similarly, Toll-like receptors (TLR) are associated with activation of the innate immune response; however, it is unclear whether TLR expression is altered in gamma delta T-cells after major burn injury. To study this, male C57BL/6 mice were subjected to burn injury (25% TBSA) and 1 or 7 days thereafter, blood and spleen cells were isolated and subjected to FACs analysis for TLRs and other phenotypic markers (gamma delta TCP, alpha beta TCF CD69, CD120b). A marked increase in the number of circulating gamma delta T-cells was observed at 24 h post-burn (14% vs. 4%) and a higher percentage of these cells expressed TLR-2. TLR-4 expression was also increased post-bum, but to a lesser degree. These changes in TLR expression were not associated with altered CD69 or CD120b expression in gamma delta T-cells. The mobilization of, and increased TLR expression in, gamma delta T-cells was transient, as phenotypic changes were not evident at 7 days post-burn or in gamma delta T-cells from the circulation or spleen. The increases in TLR expression were not observed in alpha beta T-cells after burn injury. In conclusion, 24 h after burn injury mobilization of gamma delta T-cells with increased TLR expression was observed. This finding suggests that this unique T-cell population is critical in the innate immune response to injury, possibly through the recognition of danger signals by TLRs. (C) 2008 Elsevier Ltd. All rights reserved.