Histochemical identification of human T lymphocytes from paraffin sections

The alpha-naphthyl acetate esterase (ANEA) is a histochemical marker for human T lymphocytes in cell smears and frozen tissue sections. We have now applied the ANAE method to paraffin-embedded tissue sections. We first demonstrated with cytocentrifuged cell smears of blood leukocytes that the ANAE activity is preserved upon prolonged storage in formol calcium, Holt's buffer, acetone, xylene, and heat. When the tissue sections were similarly processed and embedded in paraffin, the ANAE positive (T) lymphocytes were identified by their distinct display of one or more reddish-brown reaction dots in the cell cytoplasm. ANAE positive mononuclear phagocytes were easioy distinguished from the T lymphocytes by their diffuse, sodium fluoride-sensitive pancytoplasmic reaction. The extension of the ANAE method to paraffin-embedded tissue sections with superior morphological integrity, makes it possible to apply it in practical biopsy pathology.