GM-CSF is a multifunctional cytokine which has a wide spectrum of biological activity in both innate and adaptive immune responses.8 Studies have reported that there are high levels of GM-CSF in the synovial fluids and blood-brain barriers of inflammatory diseases, such as rheumatoid arthritis, multiple sclerosis, and arthrosclerosis.25,28-30 Although the level of GM-CSF has been studied in many inflammatory fluids, there are few studies that have extensively investigated the level of GM-CSF in GCF. Here, CSF2 is linked to rheumatoid arthritis.