CD38 and typhoid fever: We found that, during typhoid fever, although the frequencies of CD38+-activated MAIT cells expressing CCR6 or CCR9 homing markers were increased in all TD volunteers (regardless of the dose), their expression levels in the high-dose group were significantly lower than those observed in TD volunteers from the low-dose group (Figures 6A,B; Figures S6, S7, and S15–S17 in Supplementary Material).