In a mouse model of systemic sclerosis, the IL-4-producing cell proportion was significantly higher in wild-type Tregs co-cultured with Fli1+/- fibroblasts (which overproduced IL-33) than in those co-cultured with wild-type fibroblasts, which were canceled by neutralizing anti-IL-33 antibody [46]. Here, IL4 is linked to systemic sclerosis.