Effect of local and systemic burn microenvironment on neutrophil activation as assessed by complement receptor expression and morphology.

Previously, we documented that humoral factors, especially complement products, contained in burn wound blister fluid (BF) modulate normal neutrophil (PMN) function and metabolism. The goal of the current study was to examine the effects of the local (BF) and systemic (burn serum or plasma) burn microenvironment on PMN activation as assessed by complement receptor expression and morphology. Induction of CR1 (C3b) and CR3 (iC3b) receptor expression of normal PMNs after incubation in medium, BF, or plasma (serum) from healthy volunteers or burned patients was measured using monoclonal antibodies and flow cytometry. BF (10% v/v, 37 degrees C) induced 25% more CR1 receptor expression than control or burn plasma (p less than 0.05), while the levels of CR3 expression of PMNs incubated in BF (10% or 80% v/v at 37 degrees C) was more than 300% that found when the PMNs were incubated in medium, burn, or patient plasma (p less than 0.05). The electron microscopic appearance of PMNs incubated in these fluids documented that degranulation was greater when cells were incubated in BF than medium, control, or patient plasma. These results indicate that PMN activation (CR1 and CR3 expression) is greater in cells exposed to the local (BF) than the systemic (plasma) humoral microenvironment shortly after thermal injury.