The demonstration of acid alpha-naphthyl acetate esterase activity in human lymphocytes: usefulness as a T-cell marker.

The histochemical demonstration of nonspecific acid α-naphthyl acetate esterase (ANAE) activity was evaluated as a T lymphocyte marker primarily with the sheep erythrocyte (E) assay. A distinctive staining pattern characterized T lymphocytes which could be readily distinguished from monocyte staining. The percentage of E⁺ and ANAE⁺ lymphocytes was nearly always comparable in the peripheral blood and lymphoid tissue from normal and selected patients, including those with acute and chronic lymphocytic leukemia. Divergences were noted in certain other tissues including spleen and thymus. Certain mitogen-stimulated cells lost their ANAE activity while retaining their ability to form e_n rosettes. Atypical and variable staining patterns were observed in established lymphoid cell lines. The histochemical demonstration of ANAE is simple and reproducible; preparations may be counterstained for cytomorphologic detail and mounted as a permanent record. Certain disadvantages are discussed. The method represents a practical alternative to E rosette assays. It is particularly well suited for certain routine laboratories.