Hairy cell leukaemia: observations on natural killer activity in different clinical stages of the disease

Follow-up studies of natural killer (NK) cells, NK activity and antibody dependent cellular cytotoxicity (ADCC) in the course of hairy cell leukaemia (HCL) were carried out in a series of patients affected by the disease. NK activity against K562 targets was found to be high in all the patients with non-symptomatic stable disease. On the other hand, absent or extremely low NK activity was found only in patients with symptomatic progressive disease. NK activity determined in the transitional stages showed values between these two extremes. Antibody dependent cellular cytotoxicity (ADCC) was less closely correlated with the clinical stage than NK activity. Our findings suggest that investigation of in vitro NK cell cytotoxicity might serve as a useful adjunct in determining clinical stage in HCL.