IL9 and rheumatoid arthritis: Although direct clinical trials remain limited, several studies have indirectly explored the potential of modulating the Th9/IL-9 axis in autoimmune contexts—for instance, mononuclear cells from patients with RA treated with sRANKL and M-CSF in the presence of IL-9 showed enhanced osteoclast formation and function as well as an elevated expression of MMPs (87).