KLRB1 and rheumatoid arthritis: This systemic manifestation, in addition to the expression of CD161 on natural killer T cells and mucosal-associated invariant T cells, which are activated and reduced in the peripheral blood of patients with RA (47, 48), similar to TCL31, highlights the need for experimentally confirming the role of CD161 in CD4−CD8− double-negative T cells in the inflammatory pathways of SP-RA.