RELEASE THE RECEPTORS: According to Ehrlich’s side-chain theory —depicted here in a diagram used to illustrate his lecture to the Royal Society of London in 1900—immune cells were dotted with a vast array of receptors (1), each specific to a particular substance (2). When a toxin interacted with the relevant receptor (3), the cell would be activated and would react by producing more receptors, which would then be released into the bloodstream as antibodies to neutralize the toxin (4). The theory earned Ehrlich a Nobel prize, but was later discredited and largely forgotten by immunologists.WELLCOME LIBRARY, LONDONPerhaps as a respite from his struggles with literary subjects at school, during the 1860s or early 1870s a teenage Paul Ehrlich visited the lab of his cousin Karl Weigert, a pathologist at Breslau University in what is now Wroclaw, Poland. Weigert showed Ehrlich how to stain cells with dyes in order to differentiate one type of biological tissue from another—an idea that later inspired the famed German immunologist to dream up the “side-chain theory” of cellular interaction, for which he shared the 1908 Nobel Prize in Physiology or Medicine.
Ehrlich continued to experiment with dyes after he enrolled at Breslau University in 1872. As a student working under the anatomist Wilhelm von Waldeyer, his bench was crowded with dyes, and often “his fingers and occasionally his face were colorfully smudged,” wrote Arthur Silverstein in his 2002 book, Paul Ehrlich’s Receptor Immunology: The Magnificent Obsession. Ehrlich proved his proficiency in developing new dyes by discovering a novel type of immune cell called the mast cell in 1878. Four years later he also helped to improve Robert Koch’s stain for a rod-shaped bacillus that Koch had identified as the causative agent for tuberculosis, now called Mycobacterium tuberculosis.
By that time Ehrlich was convinced that “a definite chemical character of the cell,” as he wrote in his ...
