Phylogenetic Cross-Reactivity
Definition
The reaction of an antiserum with proteins from non-target species whose proteins are structurally similar due to shared evolutionary ancestry. Cross-reactivity intensity is proportional to taxonomic closeness: a human antiserum reacts more strongly with gorilla serum than with cow serum.
- Cause
- Structural similarity from shared evolutionary ancestry
- Relationship
- Proportional to taxonomic closeness
- Example
- Human antiserum reacts more with gorilla than cow serum
- Field
- Antisera-based species identification
Common questions
How do forensic serologists control for cross-reactivity when identifying species?+
Labs use titration and absorption steps to reduce or characterise the antiserum's reactivity against closely related species before casework, and interpret a positive reaction in light of known cross-reactivity patterns rather than treating any reaction as proof of the target species alone.
Why does cross-reactivity matter more for closely related species in a case?+
Because reaction strength tracks evolutionary distance, distinguishing a human sample from a closely related primate is harder and more prone to a false or ambiguous result than distinguishing it from a distantly related species such as a cow or a bird, where cross-reactivity is minimal.
Related terms
- Absorption
- The purification technique in which a crude antiserum is mixed with antigen preparations from cross-reacting species. Cross-reactive antibodies bind those antigens and...
- Adjuvant
- A substance co-administered with an antigen to amplify the immune response. Freund's Complete Adjuvant (FCA), containing killed mycobacteria in mineral oil, is...
- Antiserum
- Serum collected from an immunised animal containing antibodies directed against a specific antigen or group of antigens. In species identification, antiserum raised...
- Monospecific Antiserum
- An antiserum that reacts exclusively with proteins from the target species after absorption against all cross-reacting species has been performed and verified....
- Titre
- The concentration of antibody in a solution, expressed as the reciprocal of the highest dilution at which agglutination is still visible. A...