Early time course of altered leukocyte response to lipopolysaccharide and peptidoglycan in porcine gunshot injury

Background: Penetrating injuries are frequently combined with polybacterial soiling. Clearance of the microorganisms depends on the ability to activate immune responses, but post‐traumatic hyporeactivity of immune cells is almost universal. The aim of this study was to map the early time course of this altered leukocyte reactivity, and to compare the reactions to subsequent Gram‐positive or Gram‐negative challenges. Methods: Twelve juvenile pigs sustained two standardized rounds, one through the right femur and one through the left upper abdomen. First aid treatment and acute surgery were started immediately. Blood samples were drawn before trauma and after 10, 30, 60, and 90 min, and thereafter stimulated in ex vivo whole blood for 3 h with lipopolysaccharide (LPS, 10 ng/ml), peptidoglycan (PepG, 1 μg/ml), or an equivalent amount of normal saline. The leukocyte response was evaluated by measurement of tumor necrosis factor (TNF)‐α, interleukin (IL)‐1 β, IL‐6, IL‐8, and IL‐10 in the supernatant. Results: In the post‐traumatic in vivo serum, the concentration of TNF‐α increased steadily (significant after 60 min). A reduced ex vivo reaction to LPS was evident after 10 min, and was statistically significant after 30 min. The lowest levels were reached after 90 min. The ex vivo synthesis of TNF‐α after stimulation with PepG remained unaltered. A similar development was seen for IL‐6. IL‐1 β levels did not change, while IL‐8 increased significantly only after 60 and 90 min. Conclusions: Trauma almost instantaneously reprogrammed circulating leukocytes. As measured with TNF‐α, a profound hyporeactivity to LPS, but not to PepG, was induced. In addition, no global down‐regulation of leukocyte function was found after stimulation with LPS.