Determination of residues at positions P4 and P9 of HIENFSDIDMGE as critical residues for HLA-DQ5 HY CTL recognition.

Irradiated HLA-DQ5 female EBV cells were incubated with various concentrations of the indicated peptides for 2 hours. After washing, HLA-DQ5 HY CTLs were added; 16 hours later, supernatant was harvested and IFN-γ content was measured. IFN-γ release by HLA-DQ5 HY CTL was completely abrogated when the amino acid at P4 or P9 was substituted by the X-homolog residue. In contrast, substitution of the isoleucin residue at P8 by the DBX-derived valine resulted in an even enhanced cytokine release by the specific CTL clone.