Wt, IDO2ko, R235W, and Y346X BALB/c mice were sensitized with oxazolone. Five days later, a CHS response was elicited by painting of oxazolone on the ears. (A) Graphs show the change in mean ear thickness ± SEM 24 h after elicitation, relative to ear thickness prior to elicitation. n=20 wt, n=13 IDO2 ko, n=13 R235W and n=9 Y346X mice. ***p<0.001, ****p<0.0001, n.s., not significant. (B) 24 hr post-elicitation, ears were sectioned and stained with hematoxylin and eosin. Representative images are shown from a total of n=5 mice per genotype. Scale bar = 100μm.