As anticipated, high frequencies of both CD4+YFP+GFP+ T cells and CD4+YFP+GFP− T cell subsets exhibited an effector T cell phenotype (CD44+CD62Llow, IL-7R−, KLRG-1−) on day 14 of infection; however, at later time points after clearance of infection (days 30 and 60) there was a significant divergence in phenotypes of CD4+YFP+GFP+ T cells and CD4+YFP+GFP− T cells, with significantly higher frequencies of CD4+YFP+GFP+ T cells exhibiting an effector T cell profile compared with CD4+YFP+GFP− T cells (Fig. 2B). Here, CD4 is linked to infection.