CHI3L1 and autoimmune disease: Based on the strong involvement of YKL-40 in inflammatory processes and autoimmune disorders, particularly given that YKL-40 production depends on IL-6 secretion and also IFNγ stimulation, we hypothesized that its expression was higher in patients with cGVHD than in transplanted patients without cGVHD and that it positively correlated with disease severity and activity.