Allelic exclusion at DNA rearrangement level is required to prevent coexpression of two distinct T cell receptor beta genes.

In mice double transgenic for functionally rearranged T cell receptor (TCR) V beta 2 and V beta 8.2 genes we found that most T lymphocytes express both TCR beta chains simultaneously. These T cells show no abnormality in thymic selection in vivo and their TCRs are capable of transducing activation signals in vitro. These results indicate that multispecific T cells may appear in the periphery if allelic exclusion of TCR beta genes is not established at the level of gene rearrangement.