Question

The line of identity in a gel immunoassay

		Indicates that  the antibody and antigen are specific for one another
		does not occur in double diffusion gel precipitation
		Occurs at the equivalence site of antibody/antigen reaction
		Both 1 and 3

Answer 1

Ans.. Both 1 and 3

when the same antigen is present in both wells each line of precipitation becomes a barrier for the antigen and antibody involved, preventing them from diffusing past the precipitin line. This shortens the precipitin line on that side of the well.

Complete fusion of precipitin lines with no spurs is called a line of identity, which indicates that the antigen in each well reacts with all the antibody capable of reacting with antigen in the other well.

double immunodiffusion test have following objectives:

1. To detect antigen-antibody complexes.
2. Describe the circumstances under which antigen-antibody complexes precipitate out.
3. Detect the presence of an antigen-specific antibody.
4. To test the similarity between antigens.