Ael is a rare blood type which has the least amount of A antigen among A subgroups

Ael is a rare blood type which has the least amount of A antigen among A subgroups. It can be detected by special tests performed to resolve the discrepancy between red cell and serum typing in routine serological typing. The presence of A antigen on Ael red cell is demonstrable only by adsorption and elution tests. An Ael individual does not secret A substance in the saliva and may have anti-A antibody in the serum which is usually less reactive with the reagent red cells than anti-B antibody. In Korea, Ael02 has been reported more frequently than other Ael alleles. We report a case of Ael02/O04 who presented as typical phenotype O with strong anti-A and anti-B antibodies and no A antigen detected even by adsorption and elution tests. The case has been proved to be Ael02/O04 by direct sequencing analysis. In individuals with history of discrepancies in the results of ABO phenotyping, ABO genotyping is needed for an accurate evaluation of their blood type.

https://pubmed.ncbi.nlm.nih.gov/18728383/#:~:text=Ael%20is%20a%20rare%20blood,by%20adsorption%20and%20elution%20tests.