A body or substance, produced within the human body or other living organism, or introduced artificially, as an antitoxin, that tends to counteract some body or substance, as certain germs or their products, which may be injurious to the organism: present in the blood and fluids of immune animals.

【生理】抗体。动物免疫系统的B细胞针对侵入体内的外来物质（例如：细菌或病毒等异类蛋白质）所产生的免疫球蛋白。抗体具有高度的专一性，可专门与某一种抗原分子相结合，而协助免疫系统杀死病原。