The T cell receptor repertoires of regulatory and conventional T cells specific for the same foreign antigen are distinct1

The relationship between the TCR repertoires of natural regulatory T (nT reg ) and conventional T (T conv ) cells capable of responding to the same antigenic epitope is unknown. Here, we used TCRβ-chain transgenic mice to generate polyclonal nT reg and T conv cell populations specific for a foreign antigen. CD4 + T cells from immunized 3.L2β +/− TCRα +/− Foxp3 EGFP mice were re-stimulated in culture to yield nT reg cells (EGFP + ) and T conv cells (EGFP − ) defined by their antigenic reactivity. Relative to T conv cells, nT reg cell expansion was delayed, although a higher proportion of viable nT reg cells had divided after 72 hours. Spectratype analysis revealed that both the nT reg and T conv cell responses were different and characterized by skewed distributions of CDR3 lengths. CDR3 sequences from nT reg cells displayed a divergent pattern of Jα usage, minimal CDR3 overlap (3.4%), and less diversity than CDR3 sequences derived from T conv cells. These data indicate that foreign antigen-specific nT reg and T conv cells are clonally distinct, and that foreign antigen-specific nT reg cells populations are constrained by a limited TCR repertoire.