TCRα reporter mice reveal contribution of dual TCRα expression to T cell repertoire and function.

It is known that a subpopulation of T cells expresses two T cell receptor (TCR) clonotypes, though the extent and functional significance of this is not established. To definitively evaluate dual TCRα cells, we generated mice with green fluorescent protein and red fluorescent protein reporters linked to TCRα, revealing that ∼16% of T cells express dual TCRs, notably higher than prior estimates. Importantly, dual TCR expression has functional consequences, as dual TCR cells predominated response to lymphocytic choriomeningitis virus infection, comprising up to 60% of virus-specific CD4 and CD8 T cells during acute responses. Dual receptor expression selectively influenced immune memory, as postinfection memory CD4 populations contained significantly increased frequencies of dual TCR cells. These data reveal a previously unappreciated contribution of dual TCR cells to the immune repertoire and highlight their potential effects on immune responses.