In-vitro induction of some features of hairy cell leukemia in chronic lymphocytic leukemia and immunocytoma cells.

In an attempt to induce in vitro differentiation we exposed cells from patients with chronic lymphocytic leukemia (CLL) and with immunocytoma (IC) to 12-0-tetra-decanoylphorbol-13-acetate (TPA) at 160 nM. After 3 to 5 days of culture cells became enlarged and the CLL cells developed a basophilic cytoplasm with an excentric nucleus. In some instances cells with many fine projections were seen. We then employed the monoclonal antibody (MAB) HD 6, which was generated against hairy cell leukemia (HCL) cells and reacts most strongly with such cells but is unreactive with plasmocytoma cells and with most CLL cells. TPA treatment induced a greatly enhanced HD 6 binding in CLL and IC cells compared to controls as demonstrated by indirect immunofluorescence. Cytochemical studies revealed that at the same time an acid phosphatase was induced, which was found to be tartrate-resistant in every instance tested. Thus, several features of HCL can be induced in CLL and IC demonstrating the close relatedness of these entities.