The morphology and cytochemistry of human T-cell subpopulations defined by monoclonal antibodies and Fc receptors.

Leu 2a+ (suppressor/cytotoxic) and Leu 3a+ (helper/inducer) T-cell subsets of normal peripheral blood lymphocytes, purified by fluorescence-activated cell sorting, respectively showed 50 +/- 22% (range 31-92%) and 82 +/- 9% (range 69-93%) dot non-specific esterase (NSE) and 48 +/- 20% (range 31-91%) and 79 +/- 10% (range 64-92%) dot acid-phosphatase (APase) staining. Mature T cells defined by monoclonal antibody (UCHT1) displayed 81% and 79% dot NSE and APase positivity, while E-rosetting cells not staining with UCHT1 showed only 15% and 10% dot-positivity and were generally larger cells with more abundant cytoplasm. Examination of Fc-rosetting cells within the different T-cell subsets showed that dot positivity was not directly related to microFc receptor (microFcR) expression; particularly among Leu 2a+ lymphocytes, many microFcR+ cells lacked dot staining. It is concluded that dot staining for hydrolytic enzymes is a marker of true T-cells (as defined by monoclonal antibodies), although a minority of such cells (approximately 20%) lack this staining pattern. Although Leu 3a+ cells display a higher percentage of dot positivity than do Leu 2a+ cells, the difference is not clinically useful, and the two cell populations are not readily distinguishable on morphological grounds. The previously reported association between dot staining and microFc receptor expression is shown to be an indirect one, attributable to the fact that most T-cells, defined by monoclonal antisera, possess microFcR whereas most E+ UCHT1- cells lack microFcR.