KLRK1 and granulomatosis with polyangiitis: CD4+ NKG2D+ T cells are associated with inflammatory diseases, such as rheumatoid arthritis (RA) 5, 6, granulomatosis with polyangiitis 7, Crohn's disease 8, 9, 10, multiple sclerosis 11 and infection by human cytomegalovirus (CMV) 12.