In HIV-infected subjects, generalized up-regulation of cell-surface MHC-I in PBMCs is associated with disease progression, chronic immune activation, and naive CD8^low T cells. MHC-I cell-surface expression was measured by the MFI of MHC-I in PBMCs from subjects in studies A, B, and C, as shown here in CD4⁺ T cells. (A) MHC-I cell-surface expression in study A (left) and study B (right); of note, differences in MHC-I MFI measurements between study A and B are because of the use of different flow cytometers with different instrument settings. (B) MHC-I cell-surface expression in CD4⁺ T cells from study C at 3 and 12 months infection (“acute” and “chronic,” respectively). (C) Correlation between MHC-I cell-surface expression and CD8α expression in naive CD8⁺ T cells in study A (left) and study B (right). P values were calculated using the Mann-Whitney test for group analysis as indicated by the horizontal bar (A). Two-tailed paired and unpaired t tests were used for longitudinal follow-up of the same subject and for group analysis, respectively (B). When the P value is not indicated on the graph, the symbols * and *** indicate that P < .05 or P < .0005 for each test, respectively. P values are indicated for Spearman rank correlation for correlation test. R² from the Pearson coefficient of correlation is also indicated.