Antigen Degradation Rate
Definition
The rate at which an antigen becomes undetectable on a dried stain, driven by protein denaturation, microbial protease activity, UV exposure, and humidity. Protein antigens (Rh, MNS) degrade far faster than carbohydrate antigens (ABO), limiting their practical forensic lifespan on scene samples.
- Driven by
- Protein denaturation, microbial proteases, UV exposure, humidity
- Protein antigens
- Rh, MNS, degrade faster on dried stains
- Carbohydrate antigens
- ABO, more stable over time
- Consequence
- Limits the practical window for typing older scene samples
Common questions
Why can a lab type an old bloodstain for ABO but not for Rh?+
ABO antigens are carbohydrate structures that resist enzymatic and environmental breakdown far better than the protein-based Rh and MNS antigens, so a stain can lose reliable Rh or MNS reactivity long before its ABO group becomes untestable.
Does humid storage speed up antigen loss more than dry storage?+
Yes. Moisture supports microbial growth and the protease activity that breaks down protein antigens, which is why forensic samples are air-dried and stored cool and dry rather than left damp or warm before testing.
Related terms
- Antithetical Antigens
- Pairs of antigens where carrying one typically excludes the other on the same protein: C and c, E and e in the...
- Discriminating Power
- The statistical ability of a typing system to distinguish one individual from another in a given population. Expressed as the probability that...
- Glycophorin
- A family of heavily sialylated red-cell glycoproteins. Glycophorin A carries M and N antigens; glycophorin B carries S and s antigens. Both...
- MNS System
- A blood group system comprising M and N antigens on glycophorin A (GYPA) and S and s antigens on glycophorin B (GYPB)....
- Rh System
- A blood group system defined by antigens on two proteins encoded by the RHD and RHCE genes on chromosome 1. The clinically...