Paul Ehrlich (German: [ˈpaʊl ˈeːɐ̯lɪç] ; 14 March 1854 – 20 August 1915) was a German physician and scientist who worked in the fields of hematology, immunology and antimicrobial chemotherapy. He shared the 1908 Nobel Prize in Physiology or Medicine with Élie Metchnikoff "in recognition of their work on immunity". Among his foremost achievements were finding a cure for syphilis in 1909 and inventing an important modification of the technique for 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 ability to diagnose numerous blood diseases.
His laboratory discovered arsphenamine (Salvarsan), the first antimicrobial drug and first effective medicinal treatment for syphilis, thereby initiating and also naming the concept of chemotherapy. Ehrlich introduced 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 standardising therapeutic serums. He was the founder and first director of the Paul Ehrlich Institute, a German research institution and medical regulatory body named for him in 1947, that is the nation's federal institute for vaccines and biomedicines. A genus of Rickettsiales bacteria, Ehrlichia, is named after him.
Ehrlich has been called "father of immunology".
Ehrlich was born 14 March 1854 in Strehlen in the Prussian Province of Silesia (now Strzelin, Poland). He was the second child of Rosa (Weigert) and Ismar Ehrlich, the leader of the local Jewish community. His father was an innkeeper and distiller of liqueurs and the royal lottery collector in Strehlen, a town of some 5,000 inhabitants. His grandfather, Heymann Ehrlich, had been a fairly successful distiller and tavern manager. Ehrlich was the uncle of Fritz Weigert and cousin of Karl Weigert.
After elementary school, Paul attended the time-honoured secondary school Maria-Magdalenen-Gymnasium in Breslau, where he met Albert Neisser, who later became a colleague. As a schoolboy (inspired by his cousin Karl Weigert who owned one of the first microtomes), he became fascinated by the process of staining microscopic tissue substances. He retained that interest during his subsequent medical studies.
Ehrlich studied medicine in Breslau and Strasbourg from 1872, with a short stay in Freiburg, and received his doctorate in Leipzig in 1878, where his doctoral advisor, Julius Cohnheim, had moved.
After obtaining his doctorate, he worked at the Charité in Berlin as an assistant medical director under Theodor Frerichs, the founder of experimental clinical medicine, focusing on histology, hematology and colour chemistry (dyes).
He married Hedwig Pinkus (1864–1948) in 1883 in the synagogue in Neustadt (now Prudnik, Poland). The couple had two daughters, Stephanie and Marianne. Hedwig was a sister of Max Pinkus, who was an owner of the textile factory in Neustadt (later known as ZPB "Frotex"). He settled in the villa of the Fränkel family on Wiesenerstrasse in Neustadt.
After completing his clinical education and habilitation at the prominent Charité medical school and teaching hospital in Berlin in 1886, Ehrlich travelled to Egypt and other countries in 1888 and 1889, in part to cure a case of tuberculosis which he had contracted in the laboratory. Upon his return he established a private medical practice and small laboratory in Berlin-Steglitz. In 1891, Robert Koch invited Ehrlich to join the staff at his Berlin Institute of Infectious Diseases, where in 1896 a new branch, the Institute for Serum Research and Testing (Institut für Serumforschung und Serumprüfung), was established for Ehrlich's specialisation. Ehrlich was named its founding director.
In 1899 his institute moved to Frankfurt am Main and was renamed the Institute of Experimental Therapy (Institut für experimentelle Therapie). One of his important collaborators there was Max Neisser. In 1904, Ehrlich received a full position of honorary professor from the University of Göttingen. In 1906 Ehrlich became the director of the Georg Speyer House in Frankfurt, a private research foundation affiliated with his institute. Here he discovered in 1909 the first drug to be targeted against a specific pathogen: Salvarsan, a treatment for syphilis, which was at that time one of the most lethal and infectious diseases in Europe. In 1914, Ehrlich was awarded the Cameron Prize of the University of Edinburgh. Among the foreign guest scientists working with Ehrlich at his institute were two Nobel Prize winners, Henry Hallett Dale and Paul Karrer. The institute was renamed Paul Ehrlich Institute in Ehrlich's honour in 1947.
In 1914, Ehrlich signed the Manifesto of the Ninety-Three which was a defence of Germany's World War I politics and militarism. On 17 August 1915 Ehrlich suffered a heart attack and died on 20 August in the Hessian town of Bad Homburg. Wilhelm II the German emperor, wrote in a telegram of condolence, "I, along with the entire civilized world, mourn the death of this meritorious researcher for his great service to medical science and suffering humanity; his life's work ensures undying fame and the gratitude of both his contemporaries and posterity".
Ehrlich was buried at the Old Jewish Cemetery in Frankfurt (Block 114 N).
In the early 1870s, Ehrlich's cousin Karl Weigert was the first person to stain bacteria with dyes and to introduce aniline pigments for histological studies and bacterial diagnostics. During his studies in Strassburg under the anatomist Heinrich Wilhelm Waldeyer, Ehrlich continued the research started by his cousin in dyes and staining tissues for microscopic study. He spent his eighth university semester in Freiburg im Breisgau investigating primarily the red dye dahlia (monophenylrosanilin), giving rise to his first publication.
In 1878 he followed his dissertation supervisor Julius Friedrich Cohnheim to Leipzig, and obtained a doctorate with a dissertation entitled "Contributions to the Theory and Practice of Histological Staining" (Beiträge zur Theorie und Praxis der histologischen Färbung).
One of the most outstanding results of his dissertation investigations was the discovery of a new cell type. Ehrlich discovered in the protoplasm of supposed plasma cells a granulate which could be made visible with the help of an alkaline dye. He thought this granulate was a sign of good nourishment, and accordingly named these cells mast cells, (from the German word for an animal-fattening feed, Mast). This focus on chemistry was unusual for a medical dissertation. In it, Ehrlich presented the entire spectrum of known staining techniques and the chemistry of the pigments employed.
While he was at the Charité, Ehrlich elaborated upon the differentiation of white blood cells according to their different granules. A precondition was a dry specimen technique, which he also developed. A drop of blood placed between two glass slides and heated over a Bunsen burner fixed the blood cells while still allowing them to be stained. Ehrlich used both alkaline and acid dyes, and also created new "neutral" dyes. For the first time this made it possible to differentiate the lymphocytes among the leucocytes (white blood cells). By studying their granulation he could distinguish between nongranular lymphocytes, mono- and poly-nuclear leucocytes, eosinophil granulocytes and mast cells.
Starting in 1880, Ehrlich also studied red blood cells. He demonstrated the existence of nucleated red blood cells, which he Erythropoiesis subdivided into normoblasts, megaloblasts, microblasts and poikiloblasts; he had discovered the precursors of erythrocytes. Ehrlich thus also laid the basis for the analysis of anemias, after he had created the basis for systematising leukemias with his investigation of white blood cells.
His duties at the Charité included analysing patients' blood and urine specimens. In 1881 he published a new urine test which could be used to distinguish different types of typhoid from simple cases of diarrhea. The intensity of staining made possible a disease prognosis. The pigment solution he used became known as Ehrlich's reagent.