DNA-abnormality in hairy cell leukemia.

Spleen and light density peripheral blood leukocytes of 10 hairy cell leukemia (HCL) patients and total leukocytes of one patient and blood donor cells were stained quantitatively for cellular DNA. The DNA content of single cells was measured by flow cytometry (FC) and compared to the DNA content of sheep cells admixed as an internal control. Eight of eleven patients (72 per cent) showed deviations from blood donor DNA content. Two female patients showed increased cellular DNA content, the six male patients had hypodiploid cells. Chromosomal aberrations are therefore likely to exist in the majority of HCL patients. Separation of HCL cells into sheep erythrocyte rosette and non rosette forming cells revealed similar DNA abnormalities in both cell populations, suggesting that the leukemia encompasses cells with B and with T markers.