Selective binding of HLA-Fc to cognate hybridoma cells. (A) A2- and B7-specific reactivity of supernatants from PA2.1 and BB7.1 B cell hybridomas. Supernatants from the indicated cell culture media were tested by the single-antigen bead assay, with each row representing a bead specificity. Mean fluorescence intensity (MFI) values were graphed as a heatmap. HLA-A−specific and HLA-B−specific beads are shown in the left and right panels, respectively. (B) Binding of HLA-Fc to hybridoma cells. PA2.1 (upper panel of scatter plots) and BB7.1 (lower panel) cells were either untreated or treated with A2Fc, A2Fc-LALAPG, or B7Fc. Cells were stained with the indicated fluorochrome-conjugated antibodies (plots are pregated on viable cells [7-AAD⁻]). Numbers in scatter plots are the percentage of double-positive cells (IgG1⁺ and IgG2a⁺). All IgG subclasses were murine (mIgG). Plots are representative of at least 2 independent experiments.