passages.id: split_4_validation_739_passage
passages.type: progene_text
passages.text: In an attempt to identify the amino acid position(s) of the HLA-C - specific p58.1 / p50.1 natural killer cell receptors that determine the binding affinity for their ligand , we used soluble fusion proteins formed by the ectodomain of either receptor and the Fc portion of human IgG1 .