At this point, Groh et al. reported a substantial number of peripheral and synovial CD4+CD28− T cells, which expressed the activating receptor NKG2D in patients with rheumatoid arthritis; moreover, this population promoted the cytotoxic damage against synoviocytes with anomalous expression of NKG2D ligands [21]. This evidence concerns the gene KLRK1 and rheumatoid arthritis.