T cells expressing particular γ and δ chain V regions are developmentally controlled
First T cells during embryonic development:  γδ T cells
Fetal thymic “waves”
 
1st  wave: populates adult epidermis: dendritic epidermal T cells (dETCs)
2nd wave: epithelia of the reproductive tract
Canonical rearrangements; no N-nucleotides at junctions between V, D, and Jè Absence of TdT from these fetal T cells
Adult thymus
γδ T cells are produced continuously after initial waves; much more junctional diversity, N segments and V gene usage; small % compared to α:ß