isohemagglutinin

Isohemagglutinins are substances found in human blood serums that cause red blood cells of others of the same species to clump together. These are part of the ABO blood group system, which categorizes individuals into four main types: O, A, B, and AB, based on the presence of A and B antigens on red blood cells and anti-A and anti-B isohemagglutinins in the serum.1

Hemagglutinins, on the other hand, are glycoproteins found in plants, invertebrates, and microorganisms that also cause red blood cells to agglutinate. Notably, hemagglutinins are surface antigens on influenza viruses, enabling them to bind to host cells and initiate infection. Mutations in the genes for hemagglutinin can lead to new strains of influenza viruses that evade antibody recognition, potentially causing epidemics or pandemics.2