Clone DR/A1B9 cross-recognizes an influenza matrix peptide. (A) Recognition of peptides Flu-Ma 58-66 and tyrosinase 368-376 by clones DR/A1B9 and DR/A1B4 was assessed in a ⁵¹Cr release assay with T2 target cells in the presence of increasing peptide concentrations. Peptide Melan-A 26-35 A27L was included as an internal control. (B) Staining of clones DR/A1B9 and DR/A1B4 with multimers^PE incorporating peptide Melan-A 26-35 A27L, Flu-Ma 58-66 or tyrosinase 368-376 was performed during 1 hr at room temperature, followed by incubation with anti-CD8^FITC mAb for an additional 20 min at 4°C.