A study by Tian et al. [64] randomly selected 49 RA patients and measured their TNF-α, IL-1β, IL-6, and IL-8 levels triggered by MSC secretions using enzyme-linked immunosorbent assay (ELISA) and real-time fluorescence-based quantitative polymerase chain reaction (qPCR). Here, IL6 is linked to rheumatoid arthritis.