The story
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: An immunologic ligand, and more specifically, not only an epitope or antigen or receptor or other binding site of the immune system but also a molecule whose binding or bonding to another (such as an antibody or receptor) is of interest for its use as an immunotherapy target or as a payload carrier in an antibody-drug conjugate. Full definition →
Etymology from Wiktionary, CC BY-SA 4.0.