The impact of DR3 microvariation on peptide binding: the combinations of specific DR beta residues critical to binding differ for different peptides.

This epitope is known to bind HLA DR(alpha, beta1)*0301 but binding to HLA DR(alpha, beta1)*0302 is only 20% of binding to the former. Binding to HLA-DRB1*0305 is about 20% of binding to HLA-DRB1*0301. DAP.3 (murine fibroblast) cells were co-transfected with DRalpha- and DRbeta-chain cDNA constructs in RSV.3 plasmids. Stable transfectants expressing high levels of HLA-DR were selected by sterile cell sorting and then cultured with long-chain biotinylated peptide (the epitope). Binding was measured on a Becton-Dickinson FacStar Plus after addition of propidium iodide to exclude unhealthy and dead cells.