The CD8 coreceptor interaction with the alpha 3 domain of HLA class I is critical to the differentiation of human cytotoxic T-lymphocytes specific for HLA-A2 and HLA-Cw4.

The CD8 coreceptor interacts with MHC class I molecules through an acidic loop in the MHC alpha 3 domain. Mutations in this region reduced binding between cells expressing mutant HLA molecules and CHO cells transfected with CD8 alpha chain, with mutations at residue 227 having the greatest effects. This study was undertaken to examine the role of the CD8-HLA interaction in the generation of primary and long-term CTLs. HLA-A0201 genes (wild type or mutated at residue 227) were transfected into a cell line that lacked expression of HLA-A or B molecules but expressed HLA-Cw4. These cells were used as stimulators for PBLs from a normal donor. Cultures were tested for cytotoxicity at various times thereafter. Transfectants expressing the HLA-A0201 mutant gene were poor stimulators of primary HLA-A2-specific CTLs. In long-term culture, HLA-Cw4-specific CTLs predominated, indicating that continuous expansion of allogeneic CTLs depends upon an efficient CD8-MHC class I interaction.