Expression of HLA class I molecules on macrophages or CD4⁺ T cells infected with Nef⁺ or Nef⁻ HIV-1. Macrophages established from monocytes and CD4⁺ T cells of an HLA-B*5101⁺ donor were infected with HIV-1 JRFL or JR-Xh and NL-432 or NL-M20A, respectively, and then cultured for 6 days. The cultured macrophages and CD4⁺ T cells were stained with anti-p24 and 4D12 anti–HLA-B5 mAbs. The surface expression of HLA-B*5101 on p24⁺ or p24⁻ cells is shown as the mean fluorescence intensity (MFI) in each figure.