Immature T lymphocytes after injury characterized by morphology and phenotypic markers.

Changes in the peripheral blood mononuclear cell (PBMC) population in patients following both thermal and nonthermal injury were defined by both morphological characteristics and surface phenotype with the monoclonal antibodies T6, OKT9, OKT10, and OKIa1, using a fluorescence activated flow cytometer with gating to separate small cells of the lymphocyte series from larger forms. Lymphocytes with surface antigens that bind T6, OKT9, and OKT10 are rarely found in the peripheral blood of adult patients, except in those with malignancies of the lymphoid system. In both burn and trauma patients the percentage of lymphocytes in the PBMC population after Ficoll-Hypaque separation was significantly reduced as compared with normal controls due to increases in the number of granulocytes, large granular lymphocytes (LGL), and monocytes, often present in immature forms. T6 cells were found in significantly greater numbers in both burn and nonthermal injury patients than in a control group using both small and wide gate settings on the fluorescence-activated flow cytometer. Significant increases in the number of T9+ cells also were observed in both groups for a prolonged period following injury. Significantly increased numbers of the T10+ and Ia1+ cells were detected in burn patients. The response to injury, therefore, involves the appearance in the peripheral blood of immature cells that may express T6, T9, T10, and Ia1 surface antigens. These cells may be present in quantities otherwise seen only in malignant disease.