Interleukin-16 expression in the peripheral blood and CD8 T lymphocytes after traumatic injury.

Background: Expressed in several pathologic conditions, interleukin (IL-16) can induce chemotaxis and regulate the activation of CD4-positive leukocytes. This study investigated the expression of IL-16 in trauma patient plasma and peripheral blood leukocytes to determine its involvement in the physiologic response to injury.

Methods: In this study, 25 consecutive patients requiring trauma team activation and 15 noninjured subjects were evaluated for plasma IL-16 by enzyme-linked immunosorbent assay and peripheral blood leukocyte expression of intracellular cytokine by flow cytometry.

Results: Trauma patient plasma IL-16 was transiently increased after injury in comparison with levels in noninjured control subjects. In patients with worse outcome, both peripheral blood T lymphocyte intracellular IL-16 levels and CD4/CD8 lymphocyte ratios were lower than those for less severely injured patients and control subjects.

Conclusion: Posttraumatic changes in IL-16 expression were found to be associated with worse patient outcome, suggesting an innate immune mechanism with a role in regulation of the T lymphocyte response to injury.