Precipitin
Definition
An antibody that forms a visible precipitate when it reacts with its specific soluble antigen. The term is used interchangeably with precipitating antibody in forensic serology. The test using such an antibody is called a precipitin test.
- Type
- Antibody
- Function
- Forms visible precipitate with soluble antigen
- Synonym
- Precipitating antibody
- Associated test
- Precipitin test
Common questions
How does a precipitin differ from an agglutinin?+
A precipitin reacts with a soluble antigen dispersed in solution to form a visible precipitate, whereas an agglutinin reacts with particulate antigens, such as antigens on the surface of cells, causing them to clump together rather than precipitate out of solution.
What role does precipitin play in forensic species identification?+
A precipitin raised against a specific species' serum proteins reacts only with blood or tissue from that species, so a positive precipitin test on unknown stains helps establish whether the source was human or a particular animal species.
Related terms
- Double Immunodiffusion (Ouchterlony)
- A gel diffusion method in which both antigen and antibody diffuse toward each other from separate wells in agar. Precipitin bands form...
- Equivalence Zone
- The range of antigen-to-antibody ratios at which binding sites on both molecules are maximally cross-linked, producing the largest lattice and the heaviest...
- Immunoelectrophoresis
- A two-step technique: proteins are first separated by electrophoresis in agar gel, then antiserum diffuses from a parallel trough and forms precipitin...
- Lattice Theory
- The structural explanation for precipitation proposed by Marrack in 1934. Multivalent antigens and bivalent antibodies can each bind more than one partner,...
- Ring Precipitation Test
- A technique in which antiserum is placed in a narrow capillary tube and antigen solution is layered carefully on top. A ring...