Expression of the acid alpha-naphthyl acetate esterase marker by activated and secondary T lymphocytes in man

Acid alpha-naphthyl acetate esterase (ANAE) activity is characteristic of resting human T lymphocytes. The expression of the ANAE marker by activated human T and B lymphocytes (blasts) and by corresponding 'secondary' lymphocytes has been investigated. Human blood lymphocytes were stimulated by selective T-cell (phytohemagglutinin (PHA) and concanavalin A (Con A)) or B-cell (Staphylococcus aureus strain Cowan 1) mitogens or in the mixed lymphocyte culture (MLC), and the percentage of blasts expressing the marker was quantiated. Whereas 95% of Con-A-activated blasts expressed the marker, approximately 25%-30% of MLC-activated blasts and only 10%-25% of PHA-activated blasts were ANAE-positive. After reversion to secondary lymphocytes, the PHA- and MLC-activated cells regained the ANAE activity, and more than 90% of the blast-derived secondary T lymphocytes were ANAE-positive. Only 2%-8% of blast cells activated by Staphylococcus aureus strain Cowan 1 were ANAE-positive. We therefore conclude that ANAE is not a reliable marker for T cells when activated cells (blasts) are considered.