Secretors

Secretors are individuals who express ABO blood group antigens in bodily secretions such as saliva, mucus, tears, and urine. In secretors, soluble ABH antigens reflect the person’s ABO type, whereas nonsecretors lack these antigens in secretions but still have them on red blood cells.

Genetics and biochemistry underpinning secretor status involve the FUT2 gene, which encodes an alpha(1,2) fucosyltransferase. This enzyme adds fucose to precursor molecules to generate the H antigen in secretions. The secretor phenotype is dominant to the nonsecretor phenotype: individuals with SeSe or Sese genotypes are secretors, while sese individuals are nonsecretors. The ABH antigens found in secretions arise when tissue-specific A or B glycosyltransferases act on the H antigen.

Testing and variation: Secretor status can be determined by detecting ABH antigens in saliva or other secretions or by genotyping FUT2. The frequency of nonsecretors varies across populations, leading to substantial genetic diversity in secretor status worldwide.

Health relevance and associations: Secretor status influences mucosal glycan patterns and can affect host–pathogen interactions. Some strains of norovirus and Helicobacter pylori interact with ABH and Lewis antigens and may show different infection patterns in secretors versus nonsecretors. Secretor status can also shape the composition of the gut microbiota and may be linked to certain disease risks in specific contexts. However, these associations are complex and not universally predictive.

Overall, secretors describe a genetically determined variation in the presence of blood group antigens in secretions, with implications for physiology, microbial interactions, and certain diagnostic or forensic contexts.