Effect of interleukin-2 on peripheral blood mononuclear cells in severely injured patients

The effect of human recombinant interleukin-2 (IL-2) on the proliferative and cytotoxic response of peripheral blood mononuclear cells was analyzed in 12 severely injured patients. The in vitro proliferative response (measured from tritiated thymidine uptake) was normal during the first post-injury week, but rapidly decreased from the second week. The cytotoxic response to natural killer cell-resistant target T24 was likewise diminished from the second week. To clarify if the defect in cytotoxic response was due to numerical reduction of precursors or to reduced responsiveness, limiting dilution assay was introduced. No post-trauma reduction in precursor numbers was observed. These data collectively suggest that, in addition to impaired IL-2 production, there is an endogenous defect in IL-2 responsiveness. In the context of high incidence of septic complications, the observations may be clinically important.