Incomplete TCR-ß allelic exclusion accelerates spontaneous autoimmune arthritis in K/BxN TCR transgenic mice.

Allelic exclusion of antigen receptor loci is a fundamental mechanism of immunological self-tolerance. Incomplete allelic exclusion leads to dual T-cell receptor (TCR) expression and can allow developing autoreactive αß T lymphocytes to escape clonal deletion. Because allelic exclusion at the TCR-ß locus is more stringent than at the TCR-α locus, dual TCR-ß expression has not been considered a likely contributor to autoimmunity. We show here that incomplete TCR-ß allelic exclusion permits developing thymocytes bearing the autoreactive, transgene-encoded KRN TCR to be positively selected more efficiently, thereby accelerating the onset of spontaneous autoimmune arthritis. Our findings highlight dual TCR-ß expression as a mechanism that can enhance the maturation of autoreactive pathogenic T cells and lead to more rapid development of autoimmune disease.