- Person
- Paul Ehrlich
- Lived
- 1854–1915
- Field
- Immunology & chemotherapy
- From
- German
The story
In his 1885 monograph The Need of the Organism for Oxygen, which he also submitted as his habilitation thesis, Paul Ehrlich introduced the new technique of in vivo staining. He injected dyes such as alizarin blue and indophenol blue into laboratory animals and examined afterwards how strongly each organ had been coloured, using the patterns to judge how much oxygen different tissues contained.
Injecting aniline dyes in this way, he noticed something odd. In some kinds of animals the dye stained every organ except the brain. Ehrlich himself put this down simply to the brain taking up less dye than other tissues, and he never believed that a special barrier existed. Yet his observations were an early clue to one.
Other scientists took up the question. An 1898 study found that bile salts injected into the blood did not affect animals' behaviour, as if they never reached the brain. Around 1900 the term blood-brain barrier began to be used, though who coined it is debated: it is often credited to Max Lewandowsky, and it may have come from the physiologist Lina Stern. In 1913 Edwin Goldmann, one of Ehrlich's own students, reversed the experiment by injecting dye directly into the fluid around the brain. This time the brain was stained but the rest of the body was not, showing that the two were separate compartments.
Today scientists know that the barrier is formed by the cells lining the brain's capillaries, joined by tight junctions and supported by astrocytes and pericytes. It lets oxygen, hormones and other small molecules pass and actively carries in nutrients such as glucose and amino acids, while keeping out germs, many large molecules and antibodies circulating in the blood.
Ehrlich's dye work also showed, in 1887, that methylene blue stains the long fibres of nerve cells, the axons. The neurologist Ludwig Edinger believed this had opened a major new topic in neurology. Simple experiments with coloured chemicals thus gave early glimpses of two key features of the brain: how its nerve cells are built and how it is shielded from the blood.
Why it matters
The blood-brain barrier is now a central concern in medicine, shaping how drugs for brain diseases such as tumours, epilepsy and dementia are designed and delivered.
About Paul Ehrlich
Nobel-winning German Jewish physician who imagined the “magic bullet”, founded chemotherapy and, with Salvarsan in 1909, produced the first effective drug against syphilis.
More about Paul Ehrlich
- Paul Ehrlich named and characterised the mast cellWhile still a young scientist, Paul Ehrlich named and characterised the mast cell, the immune cell now known to drive allergic reactions.
- Paul Ehrlich's maxim is the first rule of drug designPaul Ehrlich summed up a basic law of pharmacology in four Latin words, corpora non agunt nisi fixata: a drug acts only when it is bound to its target.
- Paul Ehrlich's dyes founded modern haematologyUsing the new synthetic dyes of the 1870s and 1880s, Paul Ehrlich learned to tell the different kinds of white blood cells apart, laying the foundations of modern blood science.
- Paul Ehrlich improved the tuberculosis test overnightThe day after Robert Koch announced the tuberculosis bacterium in March 1882, Paul Ehrlich improved Koch's method of staining it, making the deadly germ far easier to detect.
- Paul Ehrlich's "magic bullet" cured syphilisPaul Ehrlich imagined a "magic bullet" that would strike disease without harming the patient, and in 1909 his lab found Salvarsan, the first modern antimicrobial drug and first cure for syphilis.
- Paul Ehrlich treated malaria with a synthetic dyeNoticing that malaria parasites soak up methylene blue, Paul Ehrlich tried the dye as a treatment, and two patients' fevers subsided, an early step toward designed synthetic drugs.
- Paul Ehrlich foresaw antibodies and receptorsPaul Ehrlich's side-chain theory proposed that cells carry receptors that bind specific toxins, an idea about antibodies that helped earn him the 1908 Nobel Prize.
- Paul Ehrlich made diphtheria antitoxin reliableWorking with Emil von Behring in the 1890s, Paul Ehrlich devised ways to measure the strength of diphtheria antitoxin, so doctors could give children safe, reliable doses.
- Paul Ehrlich’s trypan red opened the attack on trypanosomesScreening over 100 dyes in Frankfurt, Paul Ehrlich’s team found trypan red, which killed trypanosomes in infected animals, an early chemotherapy victory that led to arsenic drugs.
Sources
- Paul Ehrlich Wikipedia
- Blood–brain barrier Wikipedia
Another act of tikkun olam. This is part of tikkun olam, the Jewish idea of repairing the world, and every one of us can add to it.