MHC I
At each pole of the peptide binding site, 2 amino acid residues are conserved, ensuring only short peptides are permitted inside the cleft. Anchoring residues also hold the peptide in place by weak electrostatic forces.
Polymorphisms exist on the peptide contact face of alpha one and two subunits.

MHC II
Much the same as MHC I, however, long peptides reside through the binding site, permitted by the "extended open conformation. There are still anchoring residues that operate by weak electrostatic forces.
Polymorphisms exist only on the peptide contact face of the beta 1 subunit.

Variation in polymorphisms creates variation in binding affinity, enabling the immune system to target a wide variety of antigens by their respective binding affinities.

The T cell receptor recognises the MHC and peptide as an entire complex

	Created by Austin Davies over 10 years ago

Lecture 2 - Immunology