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Immunity. 1999 Jun;10(6):661-71.

The selective downregulation of class I major histocompatibility complex proteins by HIV-1 protects HIV-infected cells from NK cells.

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Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA.


To avoid detection by CTL, HIV encodes mechanisms for removal of class I MHC proteins from the surface of infected cells. However, class I downregulation potentially exposes the virus-infected cell to attack by NK cells. Human lymphoid cells are protected from NK cell cytotoxicity primarily by HLA-C and HLA-E. We present evidence that HIV-1 selectively downregulates HLA-A and HLA-B but does not significantly affect HLA-C or HLA-E. We then identify the residues in HLA-C and HLA-E that protect them from HIV down-regulation. This selective downregulation allows HIV-infected cells to avoid NK cell-mediated lysis and may represent for HIV a balance between escape from CTL and maintenance of protection from NK cells. These results suggest that subpopulations of CTL and NK cells may be uniquely suited for combating HIV.

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