Expression and secretion of IL-2 receptor in trauma patients.

The high-affinity cell-surface receptor for interleukin-2 (IL-2R) consists of the 75-kilodalton (kd) chain and a 55-kd glycoprotein known as Tac. This report examines the cellular expression of IL-2R and secretion of the soluble form of Tac in immunosuppressed blunt trauma (n = 20, injury severity score -20) and thermally injured (n = 20, Total body surface area greater than 35%) patients. The percentage of IL-2R-expressing peripheral blood mononuclear cells (PBMC) in mitogen-stimulated cultures from patients and age-matched normal donors was determined by direct immunofluorescence with a monoclonal anti-Tac followed by flow cytometry analysis. Levels of soluble Tac in patient sera were measured by a monoclonal antibody-based enzyme-linked immunosorbent assay. Expression of Tac antigen by mitogen-activated PBMC cultures from blunt trauma patients was transiently reduced (by as much as 40%) in 4 of 14 patients examined. Levels of serum Tac were significantly elevated (p less than 0.05) in 15 of 20 blunt trauma patients ranging from 750 to 3000 U/mL compared with 180 to 420 U/mL in control subjects. All burn patients studied 10 to 50 days after the injury demonstrated a significant reduction (by 50% to more than 90%) in the percentage of IL-2 receptor-bearing cells. Similarly serum levels of IL-2R increased significantly (p less than 0.001 to 0.05) in all burn patients studied, reaching concentrations as high as 5500 U/mL. These results suggest that major trauma, whether mechanical or thermal, induces alterations in the T-lymphocyte activation process. However the degree and duration of such changes may vary based on the nature of the injury.