We chose to perform a head-to-head immune-enrichment from primary liver tissue resections using both, MAGE-A4 and ESK1 TCR-like antibodies. Since both target antigens MAGE-A4 and WT-1 are not expressed in hepatocytes (Human Protein Atlas, www.proteinatlas.org), the ESK1 enrichment could serve as isotype control for the MAGE-A4 antibody, and vice versa.