Immunomodulation of natural killer activity in children with acute lymphoblastic leukaemia.

Modulation of NK activity of PBLs from ALL patients was studied following exposure to IFN-alpha, staphylococcal protein A and interleukin-2. Only 52% of ALL patients responded to IFN-alpha stimulation, where the majority of controls showed positive enhancement of NK activity. Protein A failed to cause a significant stimulation of ALL patient PBLs whereas all controls showed a positive response. The majority of ALL patient and child control PBLs were however able to produce significant levels of IFN-gamma (protein A stimulation) and IFN-alpha (Sendai virus stimulation), although significantly more of both types of interferon could be induced in adult PBL samples. The ability of IL-2 to activate NK activity of ALL PBL samples showed a similar trend to IFN-alpha stimulation; thus, not all ALL patients showed positive augmentation of NK activity upon IL-2 stimulation. It is clear from these results that interferons and IL-2 may not necessarily lead to activated NK cytolytic activity, and in the present study approx. 50% of ALL patients failed to respond to lymphokine stimulation.