Was·ser·mann \ˈväs-ər-ˌmän\ August Paul von (1866–1925), German bacteriologist. Wassermann is famous for discovering a universal blood-serum test for syphilis that helped to extend the basic tenets of immunology to diagnosis. His early research dealt with cholera immunity and diphtheria antitoxin. He established a relationship between the presence of diphtheria in an individual's serum and an ability to resist diphtheria infection. In 1906 he and the German dermatologist Albert Neisser developed a test for the antibody produced by persons infected with the causative agent of syphilis. The Wassermann reaction, in combination with other diagnostic procedures, is still used to test for the disease.