CD4 and rheumatoid arthritis: Indeed, NKG2D+ CD4+ T cells, not present in healthy individuals, have been reported to be involved in the patho-physiology of several immune-mediated diseases such as rheumatoid arthritis (Groh et al., 2003), Crohn’s disease (Allez et al., 2007), Wegener’s granulomatosis (Capraru et al., 2008), and human cytomegalovirus (HCMV) infection (Saez-Borderias et al., 2006).