A feature that distinguishes gammadelta T cell subsets from most alphabeta T cells and B cells is the association of expression of single T cell receptor (TCR) gamma and delta variable (V) region gene segments with specific anatomic sites. Mice lacking the TCR Vgamma5 chain normally expressed by most dendritic epidermal T cells were shown to retain a conformational determinant (idiotype) ordinarily expressed exclusively by such Vgamma5+ cells. Conservation by shuffled gammadelta TCR chains of an idiotype associated with a specific anatomic site indicates that for TCRgammadelta, as for immunoglobulin, conformation is associated to a greater extent with the function or development of lymphocyte repertoires than is the use of particular gene segments.