page_title: Paul Ehrlich
section_title: Ehrlich’s side-chain theory
hierarchical_section_title: Paul Ehrlich / Research / Serum research / Ehrlich’s side-chain theory
caption_attribution_description: Deutsch: Paul Ehrlich, in seinem Arbeitszimmer in Frankfurt am Main. English: Paul Ehrlich in his Office in Frankfurt am Main.
context_page_description: Paul Ehrlich was a Nobel prize-winning German physician and scientist who worked in the fields of hematology, immunology, and antimicrobial chemotherapy. He is credited with finding a cure for syphilis in 1909. He invented the precursor technique to Gram staining bacteria. The methods he developed for staining tissue made it possible to distinguish between different types of blood cells, which led to the capability to diagnose numerous blood diseases.
  His laboratory discovered arsphenamine, the first effective medicinal treatment for syphilis, thereby initiating and also naming the concept of chemotherapy. Ehrlich popularized the concept of a magic bullet. He also made a decisive contribution to the development of an antiserum to combat diphtheria and conceived a method for standardizing therapeutic serums.
  In 1908, he received the Nobel Prize in Physiology or Medicine for his contributions to immunology. He was the founder and first director of what is now known as the Paul Ehrlich Institute.
context_section_description: He postulated that cell protoplasm contains special structures which have chemical side chains (today's term is macromolecules) 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 immunization. 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.
caption: Paul Ehrlich around 1900 in his Frankfurt office
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