Increased toll-like receptor 4 expression on T cells may be a mechanism for enhanced T cell response late after burn injury

Background. Burn injury is associated with a dynamic T cell response. We have previously reported an enhanced functional T cell response 14 days after burn injury. Toll-like receptors (TLR), primarily expressed on innate immune cells, have recently been identified on certain T cell subsets, including activated and memory T cells. Our hypothesis is that increased TLR4 expression on memory T cells may be a mechanism for enhanced T cell response 14 days after burn injury. Methods. Splenocytes from wild-type C57BI/6 mice were harvested 14 days after a 20% total body surface area (TBSA) scald burn or sham injury. Splenocytes ex vivo were surface stained either with monoclonal anti-CD3, anti-CD4, anti-CD8, or anti-CD44 antibodies or a two-step biotin-TLR4 monoclonal antibody-streptavidin-FITC surface stain and results analyzed by flow cytometry. Results. TLR4 expression is successfully detected on CD4(+) and CD8(+) T cells. TLR4 expression is significantly (p < 0.05) increased on CD4(+) T cells and CD8(+) T cells 14 days after burn injury. There is a significant (p < 0.05) increase in CD44(hi) (memory) CD4(+) and CD44(hi) (memory) CD8+ T cells 14 days after burn injury and this is associated with a significant (p < 0.05) increase of TLR4 expression in both T cell populations. Conclusions: This study demonstrates for the first time the potential role of TLR4 expression on memory T cells generated late after burn injury. Although further analysis is required, these data reiterate the importance of adaptive immunity and the complexity of the immune response to burn injury.