Changes in lymphocyte activity after thermal injury. The role of suppressor cells.

The high incidence of fatal septicemia associated with severe thermal injury is believed to result from a loss of immunocompetence. To detect burn-mediated immune defects, lymphocyte function in peripheral blood leukocytes from 18 individuals sustaining 20-80% full thickness thermal burns was investigated. We examined the kinetics of the mitogen responses, the development of suppressive activity, and the correlation of mononuclear cell functional abnormalities with the incidence of sepsis. Patients were divided into three groups corresponding to their clinical course. The phytohemagglutinin responses of Ficoll-Hypaque purified leukocytes from eight of these patients (group III) were normal at day 1-2 after injury, but were significantly depressed (mean 16% of normal) at days 5-10 after injury. All of these group III patients experienced multiple, severe, septic episodes, and septic mortality was 75%. The other 10 burned individuals showed either augmented (group II) or unaltered (group I) mitogen responsiveness. Concomitant with evaluation of their mitogen responses, the cells of burn patients were assessed for development of suppressive activity by addition to on-going normal mixed leukocyte reactions (MLR). Only the addition of mononuclear cells with depressed phytohemagglutinin responsiveness (group III) significantly decreased MLR proliferation (mean 80% reduction) by the previously highly responsive, normal MLR combinations. Addition of cells from group III burn patients collected immediately after injury had no suppressive effect. Addition of cells from patients in group I or II or of normal individual's cells had no suppressive effect. These experimental results strongly suggest that a suppressive mononuclear cell is at least partially responsible for the decreased immunocompetence of burn patients.