A study of the nature of "hairy" cells, with emphasis on enzymatic markers.

Studies of peripheral blood, bone marrow, and spleen cells from three patients with hairy-cell leukemia were performed. Two of the three patients had well-organized cytoplasmic, ribosome-lamellar inclusions in their leukemic cells. Blast transformation and 3H-thymidine incorporation of lymphocytes seemed to fall within normal ranges when the findings were related to the absolute numbers of lymphocytes. The enzymatic markers demonstrated in hairy cells-strong acid phosphatase activity in endoplasmic reticulum and lysosomes, marked alpha-naphthyl acetate esterase reaction, and weak beta-glucuronidase activity-as well as their phagocytosis of latex particles, indicate a common origin with monocytes or histiocytes. No decisive results were obtained by immunofluorescence. Evaluation of the significance of the formation by hairy cells of mouse erythrocyte rosettes, as well as the presence of the typical hair-like projections, may require additional knowledge concerning the membrane of these cells.