Siglec-1 levels in RA peripheral blood mononuclear cells and monocyte subpopulations were significantly increased in response to TNF-α, IFN-γ, and type II collagen stimulation and was positively correlated with clinical disease indicators (e.g., DAS28, ESR, CRP, and IgM-RF) (126). This evidence concerns the gene TNF and rheumatoid arthritis.