CTLA4 and Autoimmunity: The exonic SNP rs231775 in the CTLA4 leader peptide results in threonine to alanine change, and researchers found that the polymorphism decreased CTLA4 cell surface expression and reduced the inhibitory function of CTLA4, and the G allele reduced the ability to control T-cell proliferation [43–45].Therefore, this might confer a lesser CTLA4 function, resulting in greater T-cell activity, stronger immune response, and a higher probability of autoimmunity.