The CTLA-4 gene region on chromosome 2q33 has also been associated with T1D.  The locus that includes the CTLA-4 gene has been termed IDDM12 (see slide summarizing genome screens).  CTLA-4 is a strong candidate gene for autoimmune diseases because it encodes a T cell receptor that plays a role in controlling T cell apoptosis (programmed cell death) and is a negative regulator of T cell activation.  Specifically, an A49G polymorphism within the first exon of the CTLA-4 gene was found to be associated with development T1D.  This polymorphism appears to increase T1D risk in multiple populations, including the Italian, Spanish, French, Mexican-American, and Korean populations.