Ultrastructural cytochemical demonstration of tartrate-resistant acid phosphatase isoenzyme activity in "hairy cells" of leukemic reticuloendotheliosis.

The pathognomonic "hairy cell" of leukemic reticuloendotheliosis was studied for ultrastructural localization of tartrate-resistant acid phosphatase activity. The enzyme activity could not be demonstrated by Gomori's method, but it was readily demonstrated in the cytoplasmic vesicles and Golgi saccules of the hairy cell by substitution of naphthol AS-BI phosphoric acid for Na-beta-glycerophosphate of Gomori's medium. This apparent substrate specificity may be used as a marker for electron microscopic identification of the hairy cell, and may facilitate the study of histogenesis of leukemic reticuloendotheliosis.