To understand the co-expression pattern of CHI3L1 and S100A9 during the progression from acute to chronic colitis in vivo and what effects the extent of this induction have on colonic homeostasis, WT and CHI3L1 KO were either treated with 1 cycle of DSS for 5 days (acute colitis), or AOM/DSS (chronic colitis/CAC). Here, CHI3L1 is linked to infectious otitis media.