The expression pattern of TIGIT on the surface of NK cells demonstrates considerable variability across diverse disease contexts: In patients with gastrointestinal tumors, NK cells exhibit elevated TIGIT expression alongside diminished IFN-γ production capacity; in contrast, the NK cells of patients with rheumatoid arthritis or systemic lupus erythematosus show decreased TIGIT expression alongside increased capacity for IFN-γ production. Here, TIGIT is linked to rheumatoid arthritis.