Antigens and Antibodies. The Molecular Basis of Biological Specificity

Antigens and Antibodies. The Molecular Basis of Biological Specificity 

A person who contracts smallpox may die, as a result of the damage done to his body by the smallpox virus multiplying in his cells. If he survives he has immunity against smallpox for the rest of his life but this immunity does not extend to other viral diseases. The immunity results from the induced manufacture of specific protein molecules, called antibodies the molecules (in this case the smallpox virus particles) that induce antibody formation are called antigens. 

Human antibodies are the proteins called gamma globulin in the serum of the blood. They have molecular mass about 270,000 d. Proteins and polysaccharides foreign to the individual or the species of animals, when injected, may serve as antigens. Also, small molecules may be attached to proteins and injected to induce formation of antibodies with the power of combining specifically with them. For example, if / -amino-benzoic acid, H2NCeH4COOH, is treated with hydrochloric acid and sodium nitrate it forms the diazonium ion N= N—C6H4COOH, which 

Diagram of soluble complex of bivalent antibody with two haptens and of precipitate of antibody with a dihaptenic substance. 

It was in fact found that a substance such as diazobenzoate o-cresol, -OOCQH4NN—fj N-NNQH4COO- 

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