Editing Paul Ehrlich (section)

====Ehrlich's side-chain theory====
[[File:Paul Ehrlich Arbeitszimmer.jpg|thumb|Paul Ehrlich around 1900 in his Frankfurt office]]

Ehrlich postulated that cell protoplasm contains structures which have chemical ''side chains'' ([[macromolecule]]s) to which the toxin binds, affecting function. If the organism survives the effects of the toxin, the blocked side-chains are replaced by new ones. This regeneration can be trained, the name for this phenomenon being ''immunisation''. If the cell produces a surplus of side chains, these might also be released into the blood as antibodies.

In the following years Ehrlich expanded his side chain theory using concepts ("amboceptors", "receptors of the first, second and third order", etc.) which are no longer customary. Between the antigen and the antibody he assumed there was an additional immune molecule, which he called an "additive" or a "complement". For him, the side chain contained at least two functional groups.

For providing a theoretical basis for immunology as well as for his work on serum valency, Ehrlich was awarded the Nobel Prize for Physiology or Medicine in 1908 together with [[Élie Metchnikoff]]. Metchnikoff, who had researched the cellular branch of immunity, [[Phagocytosis]], at the [[Pasteur Institute]] had previously sharply attacked Ehrlich.