Characterization of Circulating Monocytes Expressing HLA-DR or CD71 and Related Soluble Factors for 2 Weeks after Severe, Non-Thermal Injury1,2

Background Severe injury is associated with changes in monocytes that may contribute to poor outcomes. Longitudinal characterization of monocyte response patterns after trauma may provide added insight into these immunological alterations. Methods Venous blood obtained seven times during post-injury days 1 through 13 from 61 patients with an injury severity score >20 was assessed by flow cytometry for monocytes (CD14+) expressing HLA-DR or CD71 (transferrin receptor) and for circulating levels of interleukin (IL) 1α, IL-1β, IL-6, soluble CD14 (sCD14), tumor necrosis factor-α (TNF-α), prostaglandin E 2 (PGE 2 ), thromboxane B 2 (TXB 2 ), and endotoxin. Urine neopterin was measured by high-pressure liquid chromatography, expressed as a neopterin-creatinine ratio. Results Trauma patients had leucocytosis days 1 through 13, monocytosis days 5 through 13, reduced proportions of CD14+HLA-DR+ cells days 2 through 5, and elevated proportions of CD14+CD71+ cells days 1 through 13. Neopterin was elevated all days, peaking on day 10. sCD14 was elevated days 2 through 13, and there were sporadic elevations of IL-1α, IL-1β, IL-6, TNF-α, PGE 2 , TXB 2 , and endotoxin. Sepsis syndrome patients ( n = 6) had larger and more prolonged reductions in CD14+HLA-DR+ cells and higher neopterin values, in comparison with uneventful patient outcomes. Conclusions Altered proportions of monocytes expressing HLA-DR and CD71 and elevated sCD14 and urine neopterin levels, for up to 2 weeks after severe injury, underscores an extended period of profound immunological effects. Additional studies to more fully assess temporal monocyte response patterns after severe injury, including activation, may be warranted.