Suppressor cell activity after major injury: indirect and direct functional assays.

In vitro responses to streptokinase-streptodornase (SKSD), mumps, and mixed lymphocyte culture (MLC) in 19 burned and 13 multitrauma patients were studied sequentially by lymphocyte tritiated thymidine incorporation and compared to responses of 28 normals. Mean responses to SKSD remained significantly depressed from normal for up to 14 to 28 days following injury: MLC responses, significantly depressed at 48 hours, recovered promptly to normal levels. Because of evidence that the proliferative capacity of the T-cell population to soluble antigens is contained within the inducer subpopulation while both inducer and suppressor subpopulations respond in MLC, the observed increase in MLC responses, coupled with a sustained depression of SKSD and mumps responses, suggests activation of a population of suppressor cells. In a direct assay of suppressor cell function, lymphocytes from three or four multitrauma patients incubated in a two-way MLC with normal lymphocytes significantly suppressed PHA responsiveness, confirming the findings of the direct assay.