IDO1 and hyperinsulinemic hypoglycemia, familial, 4: Other documented mechanisms underlying Th17 deficiency during HIV/SIV infections include (i) altered trafficking potential of memory Th17 cells into mucosal sites [26,27]; (ii) increased ratios between regulatory T-cells versus Th17 cells at mucosal level due to enhanced indoleamine 2,3-dioxygenase 1 (IDO)-mediated tryptophan catabolism by mucosal dendritic cells (DC) [28,29]; and/or (iii) depletion of mucosal CD103+ DC [30], a subset involved in Th17 differentiation [31,32].