CHI3L1 and bacterial infectious disease: For example, Chi3l1 promotes T cell helper 2 (Th2) -induced inflammation in response to an allergen challenge [43], Hc and C3 together constitute crucial elements of the complement system which mediates several immune responses to target foreign pathogens [44], while Lcn2 [45] and Lyz factors [46] have important roles in the immune response to bacterial infection.