Six unrelated HLA-DR-matched adults recognize identical CD4+ T cell epitopes from influenza A haemagglutinin that are not simply peptides with high HLA-DR binding affinities.

HA peptide 20 was identified through affinity binding with HLA DR0701 molecules using a cut off of < 10uM. Though relative binding affinity was high, this peptide was not recognized by the CD4+ T cell lines of immunized donors. HA peptide 20 was identified through affinity binding with HLA DR0701 molecules using a cut off of < 10uM. The IC(50) for HA peptide 20 was 4200nM. Though relative binding affinity was high, this peptide was not recognized by the CD4+ T cell lines of immunized donors.