Burn enhances toll-like receptor induced responses by circulating leukocytes

Burn and toll-like receptors (TLR) are associated with innate immune system activation, but the impact of burn on TLR-induced inflammation responses by circulating leukocytes is unknown. To study this, C57BL/6 mice were subjected to burn (3(rd) degree, 25% TBSA) or sham procedure and 1-7 days later blood was collected. Whole blood cell suspensions were incubated for 24 hr in the presence of zymosan (TLR-2 agonist) or LPS (TLR-4 agonist). The blood cultures were responsive to TLR2 and TLR4-mediated activation, resulting in the production of IL-6, IL-10, IL-17, TNF-α, MIP-1α, MIP-1β, KC and RANTES. TLR2-induced KC and MIP-1β production was greater in the burn group at 3-7 days post-injury, whereas IL-6, IL-10, KC and MIP-1β were greater for TLR4-induced activation after burn. In conclusion, circulating leukocytes were responsive to TLR-induced activation and TLR-mediated inflammatory responses were enhanced 3-7 days post-injury, as evidenced by increased production of these inflammatory mediators.