IL17A and infection: The reduced production/induction of IL17 and IL22 in both the blood and genital tract of HESN participants might be causally related to HIV exposure without infection, since both Th17 and Th22 cell subsets are enriched at mucosal sites and may be particularly HIV susceptible [12], [19], [43], [44], [45] (although not all studies have found this [20]).