Secretor
Definition
An individual whose ABO blood group antigens are expressed on red blood cells and also released into body fluids such as saliva, semen, and vaginal secretions. Approximately 80 percent of the population are secretors. Secretor status is controlled by the FUT2 gene and is relevant to ABO typing of body-fluid stains.
- Prevalence
- Approximately 80% of people in most studied populations are secretors
- Genetic control
- Secretor status is governed by the FUT2 gene (also called the Se gene)
- Fluids involved
- Saliva, semen, and other body secretions contain blood-group antigens in secretors
- Biochemistry
- Secretory fucosyltransferase enzyme produced by functional FUT2 alleles releases antigens into fluids
Common questions
What is a secretor in forensics?+
A secretor is a person who sheds water-soluble ABO blood-group antigens into body fluids like saliva and semen. This happens because they carry at least one functional copy of the FUT2 gene, which produces an enzyme that releases these antigens into secreted fluids.
Why do secretors matter in forensic investigations?+
A secretor's body fluids can be typed using ABO blood groups even when they don't contain actual blood cells. This makes saliva, semen, or other fluids at a crime scene valuable for identifying individuals or excluding suspects.
How common are secretors?+
About 80 percent of people in most studied populations are secretors. This means most people will have detectable blood-group substances in their body fluids, making secretor status a useful discriminating feature in forensic serology.
Related terms
- Acid Phosphatase (AP)
- An enzyme present at high concentrations in seminal plasma. The Brentamine Fast Violet B (or SERI AP) spray test detects acid phosphatase...
- Alpha-Amylase
- Salivary enzyme. Detected by starch-iodine (clear zone in blue background) or the Phadebas reagent (blue colour from dye-linked starch). Concentration in saliva...
- Alpha-Amylase (Salivary Isoform)
- An enzyme present in saliva at concentrations several orders of magnitude higher than in other body fluids. Detected immunologically using anti-human salivary...
- Barberio Test
- Presumptive semen test. Saturated picric acid reacts with spermine to form yellow rhombic spermine picrate crystals.
- Blood-Group Substance
- Soluble ABO antigens (A substance, B substance, H substance) present in the body fluids of secretors. Chemically distinct from the glycolipid-bound cell-surface...
- Florence Test
- Presumptive semen test. Iodine plus potassium iodide reacts with choline in semen to form dark-brown rhombic / needle-shaped choline iodide crystals.
- FUT2 Gene
- The Fucosyltransferase 2 gene on chromosome 19q13, encoding the alpha-1,2-fucosyltransferase enzyme responsible for adding fucose to type-1 chain precursors in secretory tissues...
- Hp, Gc, Tf
- The classical serum-protein polymorphism panel: haptoglobin (binds free haemoglobin; Hp1-1, Hp2-1, Hp2-2 phenotypes), group-specific component (vitamin D binding protein, Gc1F / Gc1S...
- Inhibition Agglutination Assay
- A serological technique for detecting soluble antigens in body-fluid extracts. Known antibody is incubated with the stain extract; if the target antigen...
- Inhibition Index
- A quantitative measure of PCR inhibitor burden in a DNA extract, derived from the Ct shift of an internal positive control (IPC)...
- Isoenzyme / Polymorphism
- Different molecular forms of the same enzyme separable by electrophoresis. Forensic polymorphic markers have several common alleles in the population, so a...
- Lateral-Flow Immunochromatographic Strip
- A point-of-care format immunoassay in which a sample migrates along a nitrocellulose membrane past a labelled antibody zone and a capture antibody...
Explained in these topics
- Body Fluids, RBC Enzymes and Serum Proteins of Forensic SignificancePerson who secretes water-soluble ABH blood-group substances into saliva, semen and other body fluids. About 80% of the Indian population are secretors; status...
- Immunological Methods in Sexual Assault InvestigationsAn individual whose ABO blood group antigens are expressed on red blood cells and also released into body fluids such as saliva, semen, and vaginal secretions....
- Secretor Status and Its Forensic ValueAn individual who expresses ABO blood-group antigens in soluble form in body fluids, due to carrying at least one functional FUT2 allele encoding a secretory f...