CSF2 and rheumatoid arthritis: In this review, we discuss how autoimmune Th17 cells instigate FLSs and innate lymphoid cells (ILCs) in the synovial tissue to initiate and maintain autoimmune arthritis in SKG mice (6), an animal model of RA, how arthritogenic Th17 cells differentiate toward pathogenic GM-CSF producing cells in RA, and how regulatory T (Treg) cells become functionally unstable in inflamed RA joints.