Due to the fact that NK cells are also implicated in autoimmune disorders such as multiple sclerosis (Morandi et al., 2008), rheumatoid arthritis (Ahern and Brennan, 2011), and type I diabetes (Dotta et al., 2007), deregulation of SHP-1 activity may be a factor affecting normal NK cell functions against healthy cells. This evidence concerns the gene PTPN6 and rheumatoid arthritis.