Natural killer suppressor factors in sera from HIV-infected subjects

We investigated the presence of NK suppressor factors in HIV+ sera. We further investigated if gp120 could be one of the substances responsible for the impairment of NKC regulation found in HIV+ asymptomatic patients. Our results indicate that HIV+ sera inhibit significantly normal NKC in a dose-dependent way, even at concentrations as low as 1%. The inhibitory effect of HIV+ sera decreased, but was not completely removed, by adsorptions of IgG or by treatment with a MoAb against human FcIgG. Pretreatment of normal effector cells with anti-CD16 MoAb slightly reduced their cytotoxic capability, but did not modify the suppressor effect of HIV+ sera. The The preincubation of normal PBMC with recombinant gp120 had also a suppressor effect even at 10 ng/ml. Pretreatment of HIV+ sera with anti-gp120 or anti-FcIgG MoAb reduced, but not completely, their inhibitory effect. In conclusion, HIV+ serum has a dose-dependent inhibitory effect on normal NKC. Most of this inhibition is caused by IgG, but other substances, such as gp120, can also contribute to it. Since the removal of IgG and further treatments of HIV+ sera were not able to abrogate completely the NK suppression, other serum factors still undetermined (TNF-alpha, other cytokines), should be considered.