Expression and purification of Fn14-specific 18D1-IgG1 antibody GpL fusion proteins. (A) Schemes of the various GpL-18D1-IgG1 fusion protein variants evaluated in this study. (B) The indicated anti-Flag agarose affinity purified GpL-18D1-IgG1 fusion proteins (200 ng) and a marker protein mixture containing 67 ng phosphorylase b, 83 ng albumin, 147 ng ovalbumin, 83 ng carbonic anhydrase, 80 ng trypsin inhibitor and 116 ng α-lactalbumin were resolved by SDS-PAGE and then visualized by silver staining. (C) The various GpL-18D1-IgG1 fusion proteins were analyzed by gel filtration using an aqueous SEC1 column and the following molecular weight marker proteins: bovine thyroglobulin (670 kDa), human IgA (300 kDa), human IgG (150 kDa), ovalbumin (44 kDa) and myoglobin (17 kDa).