Functional alpha and beta T cell chain receptor messages can be detected in old but not in young athymic mice.

Abstract

The expression and sequences of T cell antigen receptor (TcR) alpha and beta-chain genes were investigated in the spleens from congenitally athymic (nude) mice. A small number of Thy-1+ cells (approximately 7.0%) was found in nylon wool-enriched spleen cells from young (8 weeks old) nude mice but no L3T4 or Lyt-2 surface antigens were detected. These nude mice expressed only a low level of 1.0-kb beta-chain mRNA and little or no alpha-gene transcripts. On the other hand the number of Thy-1+ spleen cells increased slightly (to 24%) in old (20 weeks old) nude mice and a small number of L3T4+ (10%) and/or Lyt-2+ (5%) cells were detectable. "Full length" 1.7-kb alpha-chain and 1.3-kb beta-chain messages could be found in nylon wool-enriched spleen cells from old nude mice. Sequence analysis of the cDNA revealed that no functional alpha and beta-chain genes can be detected in the spleen cells of young athymic mice while some of the old mice with nu/nu genotype are composed of completely rearranged V-(D)-J-C-gene segments which encode potentially functional proteins. Interestingly, two of three independent cDNA clones encoding the alpha chain used the same V alpha and J alpha-gene segments. These results suggest that extrathymic TcR alpha and beta-chain gene rearrangements do occur, though slowly, to some extent, in nude mice and may be responsible for the limited antigen and/or H-2-related T cell functions in these old athymic mice. The data further suggests that the TcR repertoire in athymic mice may also be limited.