Selection of the T Cell Repertoire in the Thymus
The T cell αβ receptor (αβTCR) generally recognizes a ligand composed of a fragment of antigen complexed to a product of the major histocompatibility complex (MHC). Although the precise nature of the binding of the receptor to its ligand is unknown the available data, including the recently solved structure of a human class I MHC molecule (Bjorkman et al. 1988), suggest a complex interaction in which the binding depends on the contact of residues in both the MHC and antigen portion of the ligand with the variable portion of the αβTCR. The polymorphic residues of the MHC molecule appear to be particularly important in this interaction because a particular βTCR which recognizes an antigen bound to one allelic form of an MHC molecule is unlikely to recognize the same antigen bound to a different allelic form of the MHC molecule. This phenomenon has been called “MHC restricted” antigen recognition.
KeywordsMajor Histocompatibility Complex Negative Selection Major Histocompatibility Complex Molecule Foreign Antigen Allelic Form
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