To resolve the confusion, 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, who had moved to the Rockefeller Institute for Medical Research in New York, and as a member of a committee of the National Research Council concerned with blood grouping suggested to substitute Janskýs and Mosss systems with the letters O, A, B, and AB. There was another confusion on the use of O which was introduced by Polish physicians Ludwik Hirszfeld and German physician Emil von Dungern in 1910. It was never clear whether it was meant for the figure 0, German null for zero or the upper case letter O for ohne, meaning without; Landsteiner chose the latter. In 1928 the Permanent Commission on Biological Standardization adopted Landsteiners proposal and stated:The Commission learns with satisfaction that, on the initiative of the Health Organization of the League of Nations, the nomenclature proposed by von Dungern and Hirszfeld for the classification of blood groups has been generally accepted, and recommends that this nomenclature shall be adopted for international use as follows: 0 A B AB.
To facilitate the change from the nomenclature hitherto employed the following is suggested:
Jansky ....0(I) A(II) B(III) AB(IV)
Moss ... O(IV) A(II) B(III) AB(I)This classification became widely accepted and after the early 1950s it was universally followed.Hirszfeld and Dungern discovered the inheritance of blood types as Mendelian genetics in 1910 and the existence of sub-types of A in 1911. In 1927, Landsteiner, with Philip Levine, discovered the MN blood group system, and the P system. Development of the Coombs test in 1945, the advent of transfusion medicine, and the understanding of ABO hemolytic disease of the newborn led to discovery of more blood groups. As of 2020, the International Society of Blood Transfusion (ISBT) recognizes 41 blood groups. Society and culture
A popular pseudoscientific belief in Eastern Asian countries (especially in Japan and South Korea) known as 血液型 ketsuekigata / hyeoraekhyeong is that a persons ABO blood type is predictive of their personality, character, and compatibility with others. Researchers have established no scientific basis exists for blood type personality categorization, and studies have found no "significant relationship between personality and blood type, rendering the theory "obsolete" and concluding that no basis exists to assume that personality is anything more than randomly associated with blood type." See also
Blood type (non-human)
Human leukocyte antigen
hh blood group

References
Further reading
Dean, Laura (2005). Blood Groups and Red Cell Antigens, a guide to the differences in our blood types that complicate blood transfusions and pregnancy. Bethesda MD: National Center for Biotechnology Information. ISBN 1-932811-05-2. NBK2261. Mollison PL, Engelfriet CP, Contreras M (1997).