Cytogenetic studies of hairy cell leukemia

Mononuclear cells from peripheral blood and spleen of four patients with hairy cell leukemia (HCL) were cultured for 1 to 10 days with and without phytohemagglutinin (PHA) stimulation. Blastogenesis and mitoses were not observed in the unstimulated cells cultured for up to 3 days. Prolonging the culture time of unstimulated cells to 7 days produced blastogenic response; a further increase in culture time to 10 days showed transformed cells but not mitoses. Poor PHA response was noted in the cultures stimulated for 3 days, but cells cultured for 7 days and then stimulated with PHA entered mitosis. Surface immunoglobulins were exhibited in 78-94% of the cells in the blood and spleen of patients. In addition, these cells had tartarate-resistant acid phosphatase and were able to phagocytize latex particles by which properties they were identified as hairy cell leukemia cells. Chromosome abnormalities were present in a proportion of cells of each patient, none of them, however, were clonal.