The MHC class I domains are structurally and genetically related to immunoglobulin and TcR domains; the outer domains (α1 and α2) are like the variable domains and the α3 domain and β2m are like the constant domains. | The MHC class I domains are structurally and genetically related to immunoglobulin and TcR domains; the outer domains (α1 and α2) are like the variable domains and the α3 domain and β2m are like the constant domains. |