Page "Side-chain theory" Paragraph 4

In an attempt to explain the origin of serum antibody, Ehrlich proposed that cells in the blood expressed a variety of receptors, which he called “ side-chain receptors ,” that could react with infectious agents and inactivate them.

Borrowing a concept used by Emil Fischer in 1894 to explain the interaction between an enzyme and its substrate, Ehrlich proposed that binding of the receptor to an infectious agent was like the fit between a lock and key.

Ehrlich suggested that interaction between an infectious agent and a cell-bound receptor would induce the cell to produce and release more receptors with the same specificity.

According to Ehrlich ’ s theory, the specificity of the receptor was determined before its exposure to antigen, and the antigen selected the appropriate receptor.

Ultimately all aspects of Ehrlich ’ s theory would be proven correct with the minor exception that the “ receptor ” exists as both a soluble antibody molecule and as a cell-bound receptor ; it is the soluble form that is secreted rather than the bound form released.