Nonsecretors

Nonsecretors are individuals who do not secrete ABH blood group antigens into bodily fluids such as saliva and mucus, due to a nonfunctional FUT2 gene. They are contrasted with secretors, who produce these antigens in secretions. Although ABH antigens may be absent in secretions, most nonsecretors still express ABO antigens on red blood cells.

Genetics and testing outline how secretor status is determined. An individual is a secretor if at least one functional FUT2 allele is present; a nonsecretor has two nonfunctional FUT2 alleles. Inheritance is autosomal recessive. The prevalence of nonsecretors varies by population, with estimates commonly around 20–25% in people of European ancestry. Testing can be performed by saliva-based assays for ABH antigens or by FUT2 genotyping.

Clinical and research significance is primarily tied to mucosal antigen presence. Secretor status influences susceptibility to certain infections and microbial interactions. Notably, nonsecretors are resistant to some strains of norovirus that require secretor-derived antigens for binding, though other strains can infect nonsecretors. There is also evidence suggesting associations between secretor status and Helicobacter pylori colonization, gut microbiome composition, and certain inflammatory or autoimmune disease risks, but findings are not yet conclusive. Secretor status is not a diagnostic marker for disease.

Nonsecretor status illustrates how genetic variation in glycan expression at mucosal surfaces can affect host–microbe interactions and individual susceptibility to infection.