Expression of various types of MHC class I molecules on T-cell blasts infected with different HIV strains. HIV-1_SF162-infected (A-D) and HIV-1_SF33-infected (E-H) T-cell blasts were stained with human anti-HIVp24 capsid antibody (Ab) and FITC- or PE-conjugated goat anti-human IgG antibody. Levels of HLA-A2 (A,E), -B7 (B,F), -C (C,G), and -E (D,H) on the surfaces of infected cells (HIV-1 p24 antigen-positive) and uninfected cells were determined after flow cytometric analysis of cells stained with the corresponding mouse anti-human HLA class I antibody. Histograms were gated on 10⁴ infected HIV p24 antigen-positive cells (heavy solid lines) and were compared with 10⁴ uninfected CD4⁺ cells (solid lines). Results are representative of 3 separate experiments. Negative controls (dashed lines) consisted of either FITC-conjugated isotype-specific IgG (A-B, E-F), PE-conjugated goat anti-mouse IgG antibody in the absence of primary antibody (C,G) or biotin-conjugated goat anti-mouse IgG antibody and PE-conjugated streptavidin (D,H) in the absence of primary antibody.