Levels of blood and intestinal CD4⁺IL-21⁺ T cells in chronic intrarectal SIV infection of RMs. (A) The percentages (left panel) and absolute numbers (cells per microliter of blood, right panel) of circulating CD4⁺IL-21⁺ T cells were compared between intrarectally SIV-infected (○) and uninfected (●) RMs. (B) The percentages (left panel) and absolute values (expressed as fraction of total CD3⁺ T cells, right panel) of intestinal CD4⁺IL-21⁺ T cells were compared between intrarectally SIV-infected (○) and uninfected (●) RMs. Statistical analyses were performed to compare the levels of CD4⁺IL-21⁺ T cells between SIV-infected and uninfected animals.