Principle : The ELISA (enzyme linked immunosorbent assay) is a technique immuno-enzymatic detection of visualizing an antigen-antibody reaction through a colour reaction produced by the action on a substrate of an enzyme has been fixed in advance to the antibody.
The main methods are :
- Indirect
The indirect elisa is used during the search for antibodies specific. it can be designed with referred to quantitative (for the protein assay varied) or qualitative (indicating the presence or absence of an antigen in the sample).
- Secondary
This technique is highly specific, is to isolate a protein that one seeks to strike a balance between two antibodies directed against it, but recognizing epitopes different.
Concretely, the first antibody is fixed on a support, followed by an incubation of the protein to be assayed. finally, the second antibody is in recognition of the complex protein/first antibody, then the protein is sandwiched between two antibodies, hence the name of this method.
A colouring more and more strong indicates that the concentration of antigen increased.
- Competition
The competition is carried out between the antigens marked (in known quantity) and not marked (quantity to be determined) for their binding to antibodies, which are in default. as well plus the antigen to be assayed are numerous, their proportion among the antigens identified by the antibodies is high, and the more the signal will be low. conversely, if the initial concentration of the antigen is low, the signal will be strong.