FIG 2.

Surface expression of PD-1 and CD38 phenotypic markers in SP CD4⁺ and CD8⁺ T cells in PB, BM, and ALN mononuclear cells before and 21 days after SIV_MAC251 infection. Representative contour plots showing PD-1 expression in SP CD4⁺ T cells (A) and CD38 expression in SP CD8⁺ T cells (B) before and 21 days after SIV infection. FSC, forward-angle light scatter. (C) Mean percentages (± standard errors) of T-cell exhaustion (PD-1) and activation (CD38) in SP CD4⁺ and CD8⁺ T cells of nine SIV-infected macaques before infection (Pre) and 21 days after infection (Post) are shown. Plots were generated by gating CD3⁺ T cells. Asterisks indicate statistically significant differences from the preinfection levels in the respective cell populations (P < 0.05).