Mechanisms underlying alterations in the Vδ1/Vδ2 ratio in the peripheral blood of chronically SIV-infected RMs. (A) SIV infection frequencies in Vδ1, Vδ2, and central memory (CD28⁺CD95⁺) CD4 T cells. The respective T-cell subsets were sorted by flow cytometry to > 98% purity, and infection frequency was measured by quantitative real-time PCR for SIV gag DNA. (B) Ki67 expression frequencies in Vδ1 and Vδ2 T-cell subsets from peripheral blood of uninfected (squares) and chronically SIV-infected (circles) RMs. (C) Volumetric Vδ1 and Vδ2 T cell counts in peripheral blood of uninfected (squares) and chronically SIV-infected (circles) RMs. P values were calculated using the Mann-Whitney U test.