Tritope model of restrictive recognition by the TCR

Given that the recognition of the allele-specific determinants expressed by MHC-encoded restricting elements (R) is germline encoded and selected, whereas the recognition of peptide (P) is somatically encoded and selected, two different combining sites must be under selection. This necessitates a multiple recognitive single T-cell receptor (TCR) with anti-R and anti-P paratopes that function coordinately to signal restrictive reactivity. The consequences of this ‘two repertoire’ postulate provides a concept of TCR structure distinct from that generally accepted at present.