[Hairy cell leukemia. Characterization of the leukemic cell: surface immunoglobulins, Fc-receptors and stimulation by mitogens (author's transl)].

In four patients with hairy cell leukemia the expression of surface immunoglobulins and Fc-receptors on the leukemic cells as well as the stimulation of the leukemic cells by various T- and B-cell mitogens was studied. Using a combined cytochemical radioautographic method the tartrate resistant isoenzyme of the acid phosphatase and immunological markers could be demonstrated simultaneously on single cells. Surface immunoglobulins were detected by 125I-labelled (Fab')2-fragments of monospecific anti-heavy-chain-antibodies. In two patients only mu- and delta-determinants were found on the isoenzyme-positive hairy cells; in one patient 86% and in the other 44% of these cells carried both heavy chains on the same cell. Another patient showed both gamma- and delta-chains on the isoenzyme-positive cells and the fourth patient gamma-chains only. When the hairy cells of one patient were cultured in vitro in human serum-free medium for 14 days, mu- and delta-determinants were found just as on freshly isolated cells suggesting that hairy cells synthesize immunoglobulins. By indirect immunofluorescence the surface-Ig on hairy cells was shown to be capped very rapidly at room temperature. The concentrated surface-Ig was found over that cytoplasmic area where most of the ingested latex particles were located. In addition, using 125I-labelled aggregated human IgG (M.W. 5-15 X 10(6)), Fc-receptors were found on virtually all of the isoenzyme-containing hairy cells in all four patients. Furthermore, a distinct, low-degree stimulation of the isoenzyme-positive hairy cells could be demonstrated when the cells were cultured in the presence of pokeweed mitogen or Lima-bean lectin (B- and T-cell-mitogens), whereas no stimulation was observed by phytohemagglutinin and concanavalin A (T-cell-mitogens). In three patients studied, isoenzyme-positive hairy cells were negative with regard to rosette formation with sheep erythrocytes.