Specifically, LIF is associated with the severity of inflammatory diseases, including ankylosing spondylitis (AS) [40] and RA [41], which are characterized by high TNF-α levels and are positively correlated with inflammatory markers, such as C-reactive protein (CRP) and the erythrocyte sedimentation rate (ESR) [42, 43], indicating a proinflammatory effect of LIF in these diseases. Here, LIF is linked to rheumatoid arthritis.