Paul Langerhans (25 July 1847 – 20 July 1888) was a German pathologist, physiologist and biologist, credited with the discovery of the cells that secrete insulin, named after him as the islets of Langerhans. Eponymous terms Islets of Langerhans – Pancreatic cells which include insulin-producing cells. Langerhans discovered these cells during his studies for his doctorate at the Berlin Pathological Institute in 1869. Langerhans cells – Skin cells concerned with the immune response and which sometimes contain Langerhans granules. In 1868, Langerhans used the technique taught to him by Julius Friedrich Cohnheim to stain a sample of human skin with gold chloride and identified the cells which bear his name. From their appearance, Langerhans believed they were nerve cells. However they are a form of macrophages that were originally thought to be dendritic cells due to their morphology. Layer of Langerhans – In the same paper in which he described Langerhans cells, he described the granular cells in the exterior portion of the Malpighian layer of the epidermis, the stratum granulosum otherwise known as the Layer of Langerhans. Langerin – CD207, langerin (Cluster of Differentiation 207) is a protein which in humans is encoded by the CD207 gene. It is expressed in the Birbeck granules of Langerhans cells. Early education Langerhans was born in Berlin on 25 July 1847, the son of a physician. He later entered the renowned Evangelisches Gymnasium zum Grauen Kloster in the same city. Due to his outstanding performance he was exempted from the final oral examinations. He began his medical studies at the University of Jena and completed them in Berlin. Major scientific contributions In February 1869, he presented a thesis entitled “Contributions to the microscopic anatomy of the pancreas,” in which he refers to islands of clear cells throughout the gland, staining differently than the surrounding tissue. He noticed that these areas were more richly innervated, but he could not suggest a function, except for the incorrect hypothesis that they might be lymph nodes. One year before, still as an undergraduate, he analysed epidermal skin cells as part of an open competition organised by Berlin University. The branched skin cells resembling neuron, described in his paper entitled “On the nerves of the human skin,” remained an enigma for over a century before their immunological function and significance were recognised. Early career and disease After graduation, he accompanied the geographer Richard Kiepert to Syria, Palestine