Natural killer cell activity in childhood acute lymphoblastic leukaemia in remission

Fifteen children with acute lymphoblastic leukaemia (ALL) in remission receiving maintenance chemotherapy and 12 ALL patients off treatment and in remission were tested for natural killer (NK) cell activity in vitro. Compared with a control population the children with ALL receiving maintenance chemotherapy had low levels of NK cell activity. This effect was not due to a specific reduction in NK cell numbers since proportions of mononuclear cells detected by the monoclonal antibodies HNK-1 (Leu-7) and Leu-11a were normal. Furthermore NK cell activity in patients could only be partially increased by pre-incubation of effector cells with interferon (alpha IFN). These studies confirm the lack of NK cell activity in children with ALL and show that this phenomenon is directly related to functional NK cell impairment. Our study has further shown that this effect is transient since ALL patients off treatment and in remission showed normal levels and augmentation of NK cell activity.