In the radial immunodiffusion (RID) test system, where is the antisera located?

In the radial immunodiffusion (RID) test, the antisera is incorporated directly into the agar gel where the samples will diffuse. This gel serves as a medium for the antigen or antibody to migrate through, allowing for the formation of a precipitin ring upon reaction between the antigen in the test sample and the antibody present in the gel.

In this system, the agar gel is uniformly mixed with the antisera before the wells are created for sample introduction. As the antigens from the samples diffuse radially away from the well, they interact with the immobilized antibodies in the gel. The resulting precipitate forms a ring whose diameter can be measured and is directly proportional to the concentration of the antigen in the sample.

This setup is essential for the quantification of specific antibodies or antigens because it enables the visualization and measurement of results in a straightforward manner. Therefore, the antisera's correct placement in the gel is fundamental for the success of the RID assay.