Although GM-CSF is widely expressed in both stromal and hematopoietic cells, recent murine studies suggest that GM-CSF from CD4+ T cells is essential in inflammatory mouse models such as experimental autoimmune encephalomyelitis (EAE), arthritis models such as collagen-induced arthritis (CIA) or SKG-arthritis, interstitial lung disease in SKG mice (SKG-ILD), peritonitis, or myocarditis [3, 4, 54, 57, 62–64]. The gene discussed is CSF2; the disease is arthritic joint disease.