CSF2 and rheumatoid arthritis: Increased concentrations of GM-CSF are found at sites of inflammation in autoimmune diseases and GM-CSF depletion has been consistently shown to be beneficial in suppressing several autoimmune disease states.34 In RA, GM-CSF in synovial fluid acts as a biomarker for disease severity and responsiveness to therapy.85 Paradoxically, GM-CSF administration, rather than suppression, has also been proven to be effective in certain instances.