Blood Groups: From ABO to 49 Blood Group Systems
A concise timeline of how human blood compatibility became progressively more complex, from Karl Landsteiner's ABO discovery to the current International Society of Blood Transfusion classification. This page separates historical discovery dates from modern ISBT system recognition where those are not the same event.
Scientific reference page. Counts can change as ISBT updates the official registry; the date of the cited release matters.
ABO was the beginning, not the end.
Karl Landsteiner's work at the start of the twentieth century explained why some human blood transfusions were compatible and others were dangerous. The following 125 years revealed additional red-cell antigens, systems and genetic mechanisms. Modern molecular techniques continue to identify previously unresolved blood-group biology: PIGZ became the 48th system in 2025, and JAMA became the 49th in 2026.
Selected milestones in human blood-group science.
This is intentionally concise. Dates below refer to the historical report or discovery of major systems/antigens; later ISBT recognition and modern molecular definition may have occurred decades afterward.
ABO
Karl Landsteiner demonstrated fundamental differences between human blood groups. ABO compatibility became the foundation of modern transfusion medicine. He received the 1930 Nobel Prize in Physiology or Medicine for the discovery of human blood groups.
M/N and P
Landsteiner and Philip Levine reported additional red-cell group differences, demonstrating that ABO was only one layer of human blood diversity.
Rh
Landsteiner and Alexander Wiener reported work that led to recognition of the Rh system, now one of the most clinically important blood-group systems.
Lutheran
The Lutheran blood-group antigen was reported, adding another clinically relevant compatibility system.
Lewis and Kell
Lewis and Kell entered the expanding map of red-cell immunohematology. Kell would become particularly important because of its potential clinical significance in transfusion and pregnancy.
S/s within MNS
Additional MNS-system antigens further expanded the known diversity of red-cell surfaces.
Duffy
The Duffy blood-group system was described, later becoming important in transfusion medicine and in understanding interactions between red cells and malaria biology.
Kidd
The Kidd system was reported. Kidd antibodies remain clinically important because they can be difficult to detect and may cause delayed hemolytic transfusion reactions.
Diego
Diego added another genetically and geographically informative red-cell system to the field.
Yt, Xg, Dombrock and others
The catalog expanded rapidly as serologic methods identified additional antigen systems and rare antibodies.
The molecular era
Genomics, exome sequencing and molecular characterization increasingly allowed unexplained antibodies and rare phenotypes to be linked to specific genes, accelerating recognition of new systems and clarifying old ones.
PIGZ — system 048
ISBT recognized PIGZ as the 48th human blood-group system. The discovery followed investigation of a patient whose plasma reacted with essentially all donor red cells tested; genomic analysis identified the underlying PIGZ variant and the GWADA antigen.
JAMA — system 049
The ISBT Working Party approved JAMA at the June 2026 congress in Kuala Lumpur. The August 2026 ISBT release formally added JAMA as system 049, associated with F11R/JAM-A and the JIMI antigen.
The 49 recognized blood-group systems.
Official ISBT system names and numbers, current to the August 2026 release. The list is included for orientation; the ISBT database remains the authoritative live registry.
“Compatible blood” is more complex than ABO and RhD.
Routine transfusion practice appropriately prioritizes the compatibility questions that matter for a specific patient and clinical context. It does not require matching every recognized antigen for every transfusion. But patients with repeated transfusion exposure, rare phenotypes or alloantibodies can become progressively harder to match.
The expanding blood-group map therefore illustrates a broader point: donor blood is an extraordinarily sophisticated biological system. Modern transfusion medicine manages that complexity with typing, antibody screening, cross-matching, donor selection and increasingly molecular methods.
Blood is a complex biological system. Oxygen delivery is one of its critical functions.
This reference page supports the broader historical perspective on transfusion, donor dependence, artificial blood, HBOCs and the evolution toward oxygen therapeutics. It does not argue against donor blood; it documents why replacing donor blood as a whole and supporting a defined physiological function are fundamentally different therapeutic objectives.
Primary and historical sources.
- ISBT Blood Group Database — August 2026 release. Official release: 49 systems and 400 antigens; JAMA added as system 049.
- ISBT Blood Group Database — live registry. Continuously updated system and antigen database; live count checked 12 Sep 2026.
- ISBT announcement: PIGZ blood group system. 22 Aug 2025.
- Mankelow TJ et al. Identification of a novel high-prevalence red blood cell antigen on junctional adhesion molecule-A defines a new blood group system. Vox Sanguinis, 2026.
- A Brief History of Human Blood Groups. Historical review containing major discovery dates for ABO, M/N, P, Rh, Lutheran, Lewis, Kell, Duffy, Kidd and other systems.
- The Nobel Prize in Physiology or Medicine 1930 — Karl Landsteiner.
Scientific and educational information. Not clinical advice. Historical dates describe reported discoveries; modern ISBT system recognition may occur later as genetics and molecular mechanisms are resolved.
Archil Jaliashvili
BHOC Therapeutics · Biological Hemoglobin Oxygen Carrier · Precision Oxygen Therapeutics
This reference timeline is part of the BHOC public scientific knowledge architecture and is maintained as a source-linked overview of the continuing evolution of blood-group science.