A cross‐species functional interaction between the murine major histocompatibility complex class I α₃ domain and human CD8 revealed by peptide‐specific cytotoxic T lymphocytes

The monomorphic cell surface glycoprotein CD8 acts as co‐receptor in the recognition of peptide‐major histocompatibility complex (MHC) class I complexes by cytotoxic lymphocytes (CTL) by binding to the monomorphic α₃ domain of the class I molecule. Positions 227 and 245 in the class I α₃ domain appear to be especially important for this interaction. Recent reports suggest there is no interspecies recognition between CD8 and MHC class I. In this study, hybrid genes from human class I HLA‐A0201 and murine class I H2K^b were transfected into human and mouse cells and tested in Cr‐release assays using HLA‐A0201‐restricted influenza A matrix peptide‐specific CTL as effectors. Transfected cells expressing chimeric genes comprising the α₁ and α₂ domains from HLA‐A0201 together with the H2K^b α₃ domain were lysed as effectively as wild‐type HLA‐A0201 and in both cases, killing was blocked by anti‐CD8 antibodyequally well. These results indicate that human CD8 can interact with the α₃ domain of murine class I to the same level as human class I.