Radial immunodiffusion (RID) or Mancini method, Mancini immunodiffusion or single radial immunodiffusion (SRID) assay is an immunodiffusion technique used in immunology to determine the quantity or concentration of an antigen in a sample

1. Single Radial immunodiffusion (SRID)
Lecturer: S. Pordel
M.Sc. of Immunology

2. § Immunodiffusion is the term applied to precipitation reactions
carried out on agar gels.
§ Radial immunodiffusion (RID) or Mancini method, Mancini
immunodiffusion or single radial immunodiffusion (SRID) assay is
an immunodiffusion technique used in immunology to determine
the quantity or concentration of an antigen in a sample.
§ Is a quantitative test.
§ Low sensitivity.
Single Radial immunodiffusion (SRID)

3.  A solution containing antibody is added to a heated medium such as agar
or agarose dissolved in normal saline. The molten medium is then
poured onto a microscope slide or into an open container, such as a Petri
dish, and allowed to cool and form a gel.
 A solution containing the antigen is then placed in a well that is punched
into the gel. The slide or container is then covered or closed to prevent
evaporation.
 The antigen is quantitated by measuring the diameter of the precipitin
circle and comparing it with the diameters of precipitin circles formed by
known quantities or concentrations of the antigen.
Con….

4. Single Radial immunodiffusion (SRID)

5. Antigen-antibody complexes

6. The ratio of antigen / antibody
Prozone : Ab
excess, precipitate
does not form
( (soluble immune
complexes)
Zone of
equivalence-
optimal ratio of
Ag/Ab – insoluble
precipitate
Post-zone – excess of
Ag (soluble immune
complexes)

7. Standard curve
 Multiple samples with
known properties are
measured and graphed.
 The samples with
known properties are
the standards, and the
graph is the standard
curve.

8. Antigen-antibody complexes are small and soluble when in
antigen excess. Therefore, precipitation near the center of the
circle is usually less dense than it is near the circle's outer edge,
where antigen is less concentrated.
If diameter of the precipitin (unknown sample) is more than
diameter of the standards diluting the sample and
repeat the test.
Con….