Reduced natural killer activity in patients with Fanconi's anemia and in family members.

Natural killer (NK) activity was measured in the peripheral blood of a family with Fanconi's anemia (FA) and compared to normal controls. One of two children with FA, and 6 of 11 family members had reduced NK activity (less than 30% with an E:T ratio of 25:1) compared to none of 40 controls (p less than 0.001). On retesting 5 of 8 family members and both children with FA had reduced endogenous NK activity compared to 0 of 5 controls (p less than 0.02). The number of NK cells determined by Leu 11b antibody was not reduced in any of the family members. Augmentation with interleukin-2 (IL-2) and alpha interferon (IFN) in those with low endogenous activity was variable. Three demonstrated no response to the 2 immunomodulators, while the 4 others increased to low normal levels. We conclude that some patients with FA and their apparently healthy relatives have reduced NK activity, which appears to be secondary to an intrinsic cell defect.