Lattice Theory
Definition
The structural explanation for precipitation proposed by Marrack in 1934. Multivalent antigens and bivalent antibodies can each bind more than one partner, generating a three-dimensional network. When the network grows beyond solubility limits, it precipitates.
- Proposed by
- Marrack
- Year
- 1934
- Mechanism
- Multivalent antigen-antibody cross-linking into a 3D network
- Outcome
- Precipitation once network exceeds solubility limits
Common questions
Why does antibody excess or antigen excess suppress precipitation under lattice theory?+
When one reactant greatly outnumbers the other, each antibody or antigen molecule tends to bind only a single partner rather than cross-linking multiple ones, preventing the large lattice network from forming, which is why the zone of equivalence produces the strongest reaction.
How does lattice theory explain why precipitation tests need a specific antigen-antibody ratio?+
The visible precipitate only forms once the cross-linked network of antigen and antibody molecules grows large enough to exceed the solubility limit, and that network only builds efficiently when both reactants are present in roughly balanced, multivalent binding proportions.
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...
- Precipitin
- An antibody that forms a visible precipitate when it reacts with its specific soluble antigen. The term is used interchangeably with precipitating...
- 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...