[Natural killer (NK) activity in patients with HIV infection]

NK activity and cells with NK phenotype (CD16+) were studied in 21 patients with HIV infection. In particular 8 patients with full-blown AIDS, 6 with AIDS related complex (ARC), 7 asymptomatic seropositive for anti-HIV antibodies were evaluated. Six subjects seronegative for anti-HIV antibodies from groups at risk for HIV infection were evaluated as well. NK activity was significantly reduced in AIDS and ARC patients but normal in asymptomatic seropositive subjects and in seronegative subjects at risk. NK cells (CD16+) were normal in AIDS patients, and in asymptomatic seropositive subjects, increased in ARC patients and in the subjects at risk. No statistical correlation was evident between the NK activity and the number of CD16+ cells in individual patients. The percentage of CD16+ cells coexpressing the HLA-DR marker i.e. CD16+ HLADR+ cells was significantly elevated only in ARC patients, and normal in the others. NK activity is the first line of defense against an invading virus and plays an important role in the immune surveillance of neoplasms. Therefore the reduced NK activity in AIDS and ARC patients can be consistent with the development of viral infections and unusual neoplasms frequently observed in such patients. The lack of correlation between defective NK activity and normal or increased number of cells with NK phenotype seems to indicate the existence of a more profound alteration in the function of NK cells rather than a simple numeric variation.