PVR and neoplasm: To determine the binding affinities of secreted SIRPα-Fc, Siglec10-Fc and TIGIT-Fc for their ligands, we purified these proteins from the supernatants of corresponding virus-infected tumor cells and constructed CD47-knockdown MC38 cells, CD24-knockdown 4T1 cells and CD155-knockdown CT26 cells using shRNA (Supplementary Fig. 5).