His third group (C) indicated absence of both A and B antigens, but contains anti-A and anti-B. The following year, his students Adriano Sturli and Alfred von Decastello discovered the fourth type (but not naming it, and simply referred to it as "no particular type"). In 1910, Ludwik Hirszfeld and Emil Freiherr von Dungern introduced the term O (null) for the group Landsteiner designated as C, and AB for the type discovered by Sturli and von Decastello. They were also the first to explain the genetic inheritance of the blood groups. Classification systems
Czech serologist Jan Janský independently introduced blood type classification in 1907 in a local journal. He used the Roman numerical I, II, III, and IV (corresponding to modern O, A, B, and AB). Unknown to Janský, an American physician William L. Moss devised a slightly different classification using the same numerical; his I, II, III, and IV corresponding to modern AB, A, B, and O.These two systems created confusion and potential danger in medical practice. Mosss system was adopted in Britain, France, and US, while Janskýs was preferred in most European countries and some parts of US. To resolve the chaos, the American Association of Immunologists, the Society of American Bacteriologists, and the Association of Pathologists and Bacteriologists made a joint recommendation in 1921 that the Jansky classification be adopted based on priority. But it was not followed particularly where Mosss system had been used.In 1927, Landsteiner had moved to the Rockefeller Institute for Medical Research in New York.
Plague or The Plague may refer to:

Agriculture, fauna, and medicine
Plague (disease), a disease caused by Yersinia pestis
An epidemic of infectious disease (medical or agricultural)
A pandemic caused by such a disease
A swarm of pest insects such as locusts
A massive attack of other pests afflicting agriculture
Overpopulation in wild animals afflicting the environment and/or agriculture
Plague, collective noun for common grackles

Historical plagues
List of epidemics
Antonine Plague, an ancient pandemic in 165–189 CE brought to the Roman Empire by troops returning from campaigns in the Near East
Black Death, the Eurasian pandemic beginning in the 14th century
Great Northern War plague outbreak, a European outbreak in the early 18th century
Great Plague of London, a massive outbreak in England that killed an estimated 20% of Londons population in 1665–1666
Plague of Athens, a devastating epidemic which hit Athens in ancient Greece in 430 BCE
Plague of Justinian, a pandemic in 541–542 CE in the Byzantine Empire
Plague Riot, a riot in Moscow in 1771 caused by an outbreak of bubonic plague

Modern plagues
Third plague pandemic or Third Plague, a major plague pandemic that began in China in 1855 until 1960
Manchurian plague (1910–11): Part of the third plague pandemic
HIV/AIDS, originally referred to as the "gay plague" when it was discovered in the 1980s (see History of HIV/AIDS)

Art, media, and entertainment
Art
Plague (painting), by Arnold Böcklin

Fictional entities
Plague, Lisbeth Salanders hacker friend and colleague in the Hacker Republic, e.g., see The Girl who Kicked the Hornets Nest#Trial
The Plague (G.I. Joe), a Cobra special forces team in the comic book G.I.