Armenian Hamster Anti-Mouse TCRβ Monoclonal antibody, clone H57-597 (HB218) Functional Grade

The pre-T-cell antigen receptor (pre-TCR), expressed by immature thymocytes, has a pivotal role in early T-cell development, including TCR beta-selection, survival and proliferation of CD4(-)CD8(-) double-negative thymocytes, and subsequent ab T-cell lineage differentiation(1-3). Whereas alpha beta TCR ligation by the peptide-loaded major histocompatibility complex initiates T-cell signalling(4), preTCR-induced signalling occurs by means of a ligand-independent dimerization event(5). The pre-TCR comprises an invariant a-chain (pre-T alpha) that pairs with any TCR beta-chain (TCR beta) following successful TCR beta-gene rearrangement(6). Here we provide the basis of pre-T alpha-TCR beta assembly and pre-TCR dimerization. The pre-T alpha chain comprised a single immunoglobulin-like domain that is structurally distinct from the constant (C) domain of the TCR alpha-chain(7); nevertheless, the mode of association between pre-T alpha and TCRb mirrored that mediated by the C alpha-C beta domains of the abTCR. The pre-TCR had a propensity to dimerize in solution, and the molecular envelope of the pre-TCR dimer correlated well with the observed head-to-tail pre-TCR dimer. This mode of pre-TCR dimerization enabled the pre-T alpha domain to interact with the variable (V) beta domain through residues that are highly conserved across the V beta and joining (J) beta gene families, thus mimicking the interactions at the core of the alpha beta TCR's V alpha-V beta interface. Disruption of this pre-T alpha-V beta dimer interface abrogated pre-TCR dimerization in solution and impaired pre-TCR expression on the cell surface. Accordingly, we provide a mechanism of pre-TCR self-association that allows the pre-T alpha chain to simultaneously 'sample' the correct folding of both the V and C domains of any TCR beta-chain, regardless of its ultimate specificity, which represents a critical checkpoint in T-cell development. This unusual dual-chaperone-like sensing function of pre-T alpha represents a unique mechanism in nature whereby developmental quality control regulates the expression and signalling of an integral membrane receptor complex.

Previously, a series of clonal alloantigen-dependent T cell lines established from the channel catfish revealed distinctly different TCRbeta rearrangements. Here, a follow-up study of the junctional diversity of these TCR gene rearrangements focuses on characterization of the genomic organization of the TCRB locus. Surprisingly, a total of 29 JB genes and two substantially different CB genes were identified downstream of a single DB gene. This is in contrast to the situation in mammals, where two clusters of a DB gene, six or seven JB genes, and a CB gene are found in tandem. The catfish CB genes are similar to36% identical at the amino acid level. All 29 catfish JB gene segments appear functional. Thirteen were used in the 19 cDNAs analyzed, of these eight were used by the 11 catfish clonal alloantigen-dependent T cell lines. As might be expected, CDR3 diversity is enhanced by N-nucleotide additions as well as nucleotide deletions at the V-D and D-J junctions. Taken together, compared with that in mammals, genomic sequencing of the catfish TCR DB-JB-CB region reveals a unique locus containing a greater number of JB genes and two distinct CB genes.