Interleukin-13 effectively down-regulates the monocyte inflammatory potential during traumatic stress.

OBJECTIVES: To determine the potential of interleukin-13 (IL-13) to modify in vitro lipopolysaccharide-induced monocyte-macrophage (MO) activity in human cells from individuals who had sustained either major mechanical or burn injury and to investigate whether the effect of IL-13 is different on MOs that have been preactivated under traumatic stress than on monocytic cells from healthy volunteers. DESIGN: Peripheral MOs from 20 controls and 16 patients after major burn or mechanical trauma were separated on days 1, 3, 5, and 7 after injury and incubated with lipopolysaccharide (1 microgram/mL) in the presence or absence of IL-13 (10 ng/mL) for 4 hours and for 20 hours. Thereafter, the following measures were determined from the culture supernatants: neopterin, nitric oxide, tumor necrosis factor alpha, IL-1 beta, IL-6, and IL-8. RESULTS: Ex vivo lipopolysaccharide-activated MOs, compared with control cells, displayed considerably enhanced inflammatory activity during the immediate posttraumatic course, with a substantial and consistent elevation of levels of tumor necrosis factor alpha and IL-6. The addition of human recombinant IL-13 to the MO cultures resulted in an effective down-regulation of the synthesis of tumor necrosis factor alpha, IL-1 beta, and IL-6 as well as IL-8, showing an average reduction of mediator production to two thirds of the value found in corresponding sole lipopolysaccharide-stimulated cultures. The impact of human recombinant IL-13 on control MOs was almost identical for IL-6 and IL-1 beta, slightly lower for IL-8, and nonexistent for tumor necrosis factor alpha. CONCLUSION: From this study and preexisting findings, we conclude that, based on its biologic properties, IL-13 should be tested as a biologic response modifier for acute states of trauma-induced host defense deficiency.