Postburn impaired cell-mediated immunity may not be due to lazy lymphocytes but to overwork.

After major trauma, including burns, patients develop a multitude of immunologic alterations, including impaired cellular immunity (CMI). Because of conflicting reports on the relationship of in vitro lymphocyte activity to the clinical course of burn patients, we studied CMI in 29 patients with a mean burn size of 41% and a mean age of 32 years. The patients' cellular response to the mitogen phytohemagglutinin and the ability of the patients' serum to suppress a normal lymphocyte mitogenic response were measured. The endogenous level of lymphocyte activity spontaneous blastogenic transformation (SBT) was measured immediately after the cells were harvested from the blood. During the first 72 hours postburn, the ability of the patients' cells to respond to mitogens in vitro decreased, while the endogenous activity (SBT) increased. Subsequent changes in the SBT, but not the mitogen-stimulated response, predicted sepsis. Although the patients' serum was mildly suppressive, these changes were not of statistical or clinical significance. It is postulated that the in vivo and in vitro CMI defects are not primarily due to a defect in the ability of the cell to be activated, but instead are due to exhaustion, desensitization, or down-regulation of these in vivo-activated cells.