Large-scale antibody expression and purification

IgA, IgG, and IgG-IgA Fc fusions were transiently expressed in CHO DP12 cells as previously described.⁵⁸ For low expressing clones, TI stable cell lines were generated. IgG and IgG-IgA Fc fusions were affinity-purified using MabSelect Sure (GE Healthcare), followed by SEC with a HiLoad Superdex 200 pg column (GE Healthcare). IgAs were affinity-purified using Capto L (GE Healthcare) followed by SEC. For IgA samples where DNA ratios successfully biased expression to mainly one oligomeric state, a HiLoad Superdex 200 pg column (GE Healthcare) was used for SEC. For IgA samples containing complex mixtures of oligomers, a 3.5 μm, 7.8 mm x 300 mm Xbridge Protein BEH 450 Å SEC column (Waters) was used for better separation of dimer and tetramer peaks.