Histochemical identification of T and B areas in paraffin-embedded lymphoid tissues by demonstration of alpha-naphthyl acetate esterase (ANAE) activity.

A strong activity of acid alpha-naphthyl acetate esterase (ANAE) in T lymphocytes and macrophages within mouse lymphoid organs is demonstrable even after paraffin-embedding, if a rapid embedding procedure with acetone as dehydrating agent is used. The lymphoid tissue structure is better preserved in paraffin sections procured after this rapid embedding procedure than in frozen sections commonly used for histochemical demonstration of ANAE. In the paraffin sections the pattern of the ANAE reaction allows a clear delineation of the T and B areas in the lymphoid organs, and the intracellular location of the focal ANAE activity in T lymphocytes is readily discernible.