Impaired Expression of Interleukin-2 Receptor (IL2R) in the Immunosuppressed Burned Patient: Reversal by Exogenous IL2

Abstract

The capability of exogenous recombinant Interleukin 2 (rIL2) to increase expression of the IL2 receptor (IL2R), and to augment the in vitro proliferative response of lymphocytes from immunosuppressed burned patients (5-80% full-thickness burns) was examined. Throughout the postburn period the percentage of IL2R-bearing cells in Concanavalin A-activated cultures of patients' peripheral blood mononuclear cells (PBMC) was measured by direct immunofluorescence with monoclonal anti-IL2R antibodies. Mitogen-induced IL2R expression was decreased by 40-90% in cultures of patients' PBMC, parallel to their reduced alloreactivity. During this period of immunosuppression supplementation of the mitogen-activated cultures with recombinant IL2 (20 U/ml) significantly increased the number of IL2R-expressing cells in all patients studied. However, IL2-induced enhancement of blastogenesis in the MLR was observed only with the patients who, in mitogen-activated cultures, sustained numbers of IL2R-endowed cells at least 50% of their baseline (the level within the first 24 hours postburn). Also, unstimulated PBMC of the same responding patients demonstrated a restoration of proliferation in the presence of rIL2. These patients were survivors. Thus the proliferative response correlated well with the number of Con A- but not rIL2-induced IL2R-expressing cells. These results suggest that in burned patients, IL2 up-regulates its receptors, but they may represent low-affinity nonfunctional receptors. Thus thermal injury appears to affect expression of functional (high-affinity) receptors.