S. Partula et al., STRUCTURE AND DIVERSITY OF THE T-CELL ANTIGEN RECEPTOR BETA-CHAIN IN A TELEOST FISH, The Journal of immunology, 155(2), 1995, pp. 699-706
Cell-mediated immunity (e.g., allograft rejection) is found in all ver
tebrates, and these reactions are known to depend on thymus-derived ce
lls in amphibian, avian, and mammalian species. The participation of p
eripheral T cell-like lymphocytes subpopulations to fish immunity is n
ow well documented, but the developmental origin, migration, and perip
heral tissue distribution of these cells remain practically unknown. T
his is mainly due to the difficulty of efficiently thymectomizing fish
at an early stage of development and to the lack of Ab strictly speci
fic for thymocytes and T cell surface Ag. One strategy for analyzing T
cell biology in fish would be to characterize the genes encoding poly
peptides homologous to the TCR molecules. This report describes cDNA c
lones from the rainbow trout (Oncorhynchus mykiss) that have sequences
very similar to amphibian, avian, and mammalian TCR beta-chains. Thre
e complete trout V beta segments belonging to different families were
analyzed; one of them had limited amino acid sequence similarity to th
e human V beta 20 family. The 10 trout beta-chain-joining segments all
retain the invariant mammalian J beta residues, and comparison of 66
V beta-J beta junctions led to the identification of a D beta-like seq
uence (GGACAGGG) that is shorter than but very similar to the chicken
D beta and mammalian D beta 1 sequences. There is considerable diversi
ty at the V beta-D beta and D beta-J beta junctions, suggesting the pr
esence of N-nucleotides. The trout C beta extracellular domain is shor
ter than mammalian C beta, and the hinge region has no cysteine residu
e. The transmembrane C beta domain contains a lysine residue that in m
ammals is thought to be involved in charged interactions with members
of the CD3 complex.