Increased susceptibility to infection due to infusion of exogenous chemotaxin

Previous studies indicate that endogenous chemotaxins, such as the chemotactic factor C5a, may modulate the function of neutrophils (PMNs) and account for increased susceptibility to infection after injury. These effects were investigated by continuously infusing rats with saline or the chemotaxin formyl-methionyl-leucyl-phenylalanine (FMLP). Rats that sustained a full-thickness burn covering 30% of total body surface area and whose wounds were inoculated with Pseudomonas aeruginosa had a significantly shorter survival when FMLP was infused (6.5 +/- 0.91 days) than did saline-infused rats (9.9 +/- 0.83 days). Rats infused with FMLP had significantly more leukocytes in their burn wounds, significantly fewer PMNs in the circulating pool, and the same number of PMNs at the site of FMLP infusion compared with the saline-treated group. These findings support the hypothesis that chemotaxins generated by tissue injury or sepsis contribute to increased susceptibility to infection.