“Radioresistant” intrathymic T cell precursors express T cell receptor C_γ4‐ and C_δ‐specific gene messages

We have studied the expression and sequences of T cell receptor γ and δ chain gene messages in intrathymic T cell precursors of mice irradiated with 600 rads. On day 7 after irradiation a high level of expression of γ and δ chain messages was detected in thymocytes which were composed of a relatively high proportion of CD3⁺CD4⁻CD^8‐thymocytes. During further development of the precursors from day 7 to day 14 after irradiation, γ and δ chain messages fell to low levels and α and β mRNA levels increased. Nucleotide sequence analysis of 14 γ and 10 δ chain complementary DNA (cDNA) in the thymocytes on day 7 revealed that there were 7 functional γ chain transcripts composed of V_γ2‐J_γ2‐C_γ2 or V_γ1‐J^γ4‐gene segments, and only 1 functional δ chain transcript composed of the V_δM23‐D_δ1‐D^δ2‐J_δl‐C_δ gene segments. The repertoire of γ chain and δ chain genes used in “radioresistant” intrathymic T cell precursors of adult mice appears to be limited.