CD38⁺ CD4⁺ T cells have a phenotype associated with cytotoxic potential.

<p>(A) Representative staining in one volunteer and (B-C) frequencies of CD38^- (black) or CD38⁺ (red) CD4⁺ T cells expressing perforin⁺, granzyme B⁺ (GrzB) or perforin⁺/granzyme B⁺ determined by flow cytometry in volunteers prior to and seven days post infection. <b>(D)</b> Eomes gene expression measured by RT-qPCR in CD38^- (black) or CD38⁺ (red) CD4⁺ T cells isolated from volunteers prior to and seven days post infection. Graphs show combined data from (A-C) 13 volunteers from two independent cohorts, (D) seven (pre) and three (post) volunteers from one cohort. Statistical differences between CD38^- and CD38⁺ CD4⁺ T cells or between pre- and post-infection were determined using the non-parametric Wilcoxon test; box and whisker plots indicate median, interquartile range and min-max; *, <i>p</i> < 0.05; **, <i>p</i> < 0.01; ***, <i>p</i> < 0.001; ****, <i>p</i> < 0.0001.