Dear Editor, The ABO blood group system, discovered by Karl Landsteiner in 1901, has been a cornerstone in transfusion medicine and immunology. The system classifies human blood into four main types: A, B, AB and O, based on the presence or absence of specific antigens on the surface of red blood cells. However, the evolutionary history of these blood types suggests that they emerged sequentially over time, with each new type arising from genetic mutations and selective pressures. This raises the intriguing possibility of the emergence of a new blood type, which we tentatively name ‘ABO Blood Group type F’ or ‘Fifth ABO Blood Group’. This article explores the hypothetical characteristics, prevalence and potential impact of this new blood type on existing blood group systems. The evolutionary timeline of ABO blood groups indicates that blood type O is the oldest, followed by A, then B and finally AB. This sequence is supported by genetic evidence showing that the A and B alleles evolved from the O allele through mutations. The emergence of new blood types has historically been driven by environmental factors, such as infectious diseases, which exerted selective pressures favouring certain blood types over others. For instance, blood type O is associated with resistance to severe malaria, while blood type A may confer resistance to smallpox.1 Given the historical pattern, it is plausible that a new blood type, type F, could emerge. This new blood type might arise from a mutation in the ABO gene, leading to the expression of a novel antigen on red blood cells. The mutation could be a result of random genetic drift or selective pressures from new environmental challenges, such as emerging infectious diseases or changes in human diet and lifestyle.2 Blood Type F would likely have a unique antigen structure, distinct from the A, B and H antigens. This new antigen could be a result of a novel glycosyltransferase enzyme that adds a different sugar moiety to the H antigen precursor.3 Individuals with Blood Type F would produce antibodies against the A, B and H antigens, similar to how individuals with blood type O produce anti-A and anti-B antibodies. However, the specificity and strength of these antibodies would need to be characterised.4 Blood Type F could be compatible with existing blood types in a manner similar to how blood type O is a universal donor. Alternatively, it might have unique compatibility requirements, necessitating the development of new transfusion protocols.5 The initial prevalence of Blood Type F would likely be low, confined to specific populations where the mutation first occurred. Over time, if the new blood type confers a selective advantage, its frequency could increase. The distribution of Blood Type F would depend on factors such as population migration, interbreeding and the nature of the selective pressures driving its spread.6 The emergence of ABO Blood type F would have significant implications for blood transfusion medicine. Blood banks would need to develop new assays to detect the F antigen and corresponding antibodies. This would require updates to existing blood typing technologies.7 Identifying and recruiting donors with Blood Type F would be crucial to ensure an adequate supply of compatible blood for patients with this blood type. Existing transfusion protocols would need to be revised to accommodate the new blood type, ensuring that patients receive compatible blood to prevent adverse reactions.8 To prepare for the potential emergence of Blood Type F, several research initiatives should be undertaken. Monitoring human populations for novel mutations in the ABO gene could provide early detection of new blood types. Investigating the immunological properties of the F antigen and corresponding antibodies would be essential for developing safe transfusion practices. Understanding the potential spread and impact of Blood Type F through epidemiological modelling could help healthcare systems prepare for its emergence. The hypothetical emergence of ABO Blood Group type F represents an exciting frontier in blood group research. While the existence of this new blood type remains speculative, the historical pattern of blood type evolution suggests that it is a possibility worth considering. By proactively studying the genetic, immunological and epidemiological aspects of new blood types, we can better prepare for the future of transfusion medicine and ensure the safety and efficacy of blood transfusions for all patients. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
Falah Hasan Obayes Al-Khikani (Mon,) studied this question.