Expression of Cγ4 T cell receptors and lack of isotype exclusion by dendritic epidermal T cell lines

Although four murine Cγ gene segments (Cγ1, 2, 3, and 4) are known to exist, the large majority of expressed γ-chains have been shown to be of the Cγ1 isotype and no evidence exists for the expression of more than one receptor by γδ TCR-bearing cells. We investigated the nature of the TCR expressed on a number of murine dendritic epidermal T cell-derived cell lines by using both Northern blot and immunoprecipitation analyses. One of these CD3⁺ cell lines (T195) expresses Cγ4, Vγ1, and δ mRNA, and its CD3-associated TCR complex can be precipitated by both anti-Cγ4 and anti-δ sera, indicating that this receptor is a Cγ4/δ heterodimer. Furthermore, we show that two cell lines (Y245, Y93) express two distinct TCR γ-chains, one derived from the Cγ4 locus, whereas the second γ-chain is probably derived from the Cγ2 locus. Together with the previous demonstration of Cγ1/δTCR on a number of dendritic epidermal T cell lines (DETC), these results indicate that such DETC are capable of expressing a variety of γδ TCR and that, in some DETC, isotype exclusion of γ-chain expression does not occur.