ALPHA‐NAPHTHYL ACETATE ESTERASE ACTIVITY IN HUMAN ADULT AND CORD BLOOD ROSETTE FORMING CELLS

: Alpha-naphthyl acetate esterase (ANAE) activity was studied in cells forming rosettes with sheep and mouse erythrocytes. In adult peripheral blood, on the average 74% of E-rosette-forming cells expressed simultaneous focal ANAE activity, whereas most cells forming rosettes with mouse erythrocytes were negative. No difference was observed in ANAE-staining proportions of active and total E-rosette forming cells in adult peripheral blood. The proportions of total and active E-rosette and M-rosette forming cells were similar in adult peripheral blood and cord blood lymphocytes. However, the mean percentage of cord blood total E-rosette-forming cells expressing ANAE activity (61%) was significantly lower (P less than 0.001) than in adult peripheral blood.