HLA-DR*1101-Bir tetramers stain CD4+ T cells specific for the MAGE-3 tumour antigen derived p39 epitope. Ability of p39-loaded HLA-DR*1101-Bir tetramers to stain a specific CD4+ TCC. (a) Clone M3 2C3.35 was assayed for IFN-γ production to different doses of p39 peptide. 104 T cells are incubated for 48 hours with 5 × 104 HLA-DR*1101+ LCL cells and the indicated doses of p39 peptide. IFN-γ in the supernatant is measured by ELISA. (b) Staining of a MAGE-3-specific T cell clone. The cells are stained at day 19 from re-stimulation with 10 μg of either CLIP-loaded or p39-loaded HLA-DR*1101-Bir tetramers for 2 hours at 37°C.