The lead mAbs bind pHLA specifically on a cell surface. Murine A20 B cells engineered to express HLA-DQ2.5 with covalently linked peptide were stained with 107, 4.7C or 4.7Cplus hIgG1 or a hIgG1 isotype control mAb (5 μg/mL). (A) Histograms show mAb binding to A20 HLA-DQ2.5 with DQ2.5-glia-α1a (TCR-like mAbs in blue, isotype mAb in turquoise), DQ2.5-glia-α2 (black) or CLIP2 (gray) (n = 2). (B) MFI of mAb binding to the complete panel of A20 B cells expressing different pHLAs; 2.12.E11 mIgG1 was included as control (n = 2). (C) Binding slopes of mAbs 107, 4.7C and 4.7Cplus binding to A20 B cells expressing HLA-DQ2.5 with DQ2.5-glia-α1a. mAbs were titrated from 16.5 nM (4-fold dilution) and binding was analyzed by flow cytometry and visualized as MFI values. Error bars illustrate mean ± SD of duplicates (n = 2–4).