Killing of human immunodeficiency virus-infected primary T-cell blasts by autologous natural killer cells is dependent on the ability of the virus to alter the expression of major histocompatibility complex class I molecules.

In the current study, we evaluated whether the capacity of HIV to modulate major histocompatibility complex (MHC) class I molecules has an impact on the ability of autologous natural killer (NK) cells to kill the HIV-infected cells. Analysis of HIV-infected T-cell blasts revealed that the decrease in MHC class I molecules on the infected cell surface was selective. HLA-A and -B were decreased on cells infected with HIV strains that could decrease MHC class I molecules, whereas HLA-C and -E remained on the surface. Blocking the interaction between HLA-C and -E and their corresponding inhibitory receptors increased NK cell killing of T-cell blasts infected with HIV strains that reduced MHC class I molecules. Moreover, we demonstrate that NK cells lacking HLA-C and -E inhibitory receptors kill T-cell blasts infected with HIV strains that decrease MHC class I molecules. In contrast, NK cells are incapable of destroying T-cell blasts infected with HIV strains that were unable to reduce MHC class I molecules. These findings suggest that NK cells lacking inhibitory receptors to HLA-C and -E kill HIV-infected CD4+ T cells, and they indicate that the capacity of NK cells to destroy HIV-infected cells depends on the ability of the virus to modulate MHC class I molecules.