antitoxin
an.ti.tox.in \.ant-i-'ta:k-s*n\ n [ISV] : an antibody formed in the body as a result of the introduction of a toxi n and capable of neutralizing the specific toxin that stimulated its production and produced commercially in animals by injection of a toxin or toxoid (as of human disease) with the resulting serum being used to counteract the toxin in other individuals