CHIT1 and cystic fibrosis: However, it would have been unethical to repeat animal experiments after the effect of the key factors investigated here in the context of fungal infection has already been established in vivo: for example, in an in vivo model of systemic candidiasis, Chit1 contributed to host resistance in mice (18), consistent with genetic chitinase deficiency of CHIT1 to associate with C. albicans colonization in patients with cystic fibrosis (32).