Precipitation Methods Immunology Review 389
METHOD
Precipitation
Ouchterlony double diffusion
Radial immunodiffusion (RID)
Rocket immunoelectrophoresis
Immunoelectrophoresis (IEP)
Immunofixation
electrophoresis (IFE)
Nephelometry
PRINCIPLE
Soluble ag combines with soluble ab to produce visible
complexes. Less sensitive than agglutination.Ags & abs diffuse from wells in gel & form precipitin lines
where they meet.Ag diffuses out of well in gel containing ab. Precipitin ring
forms. Diameter proportional to concentration of ag.Electrical charge applied to RID to facilitate migration of
ag into agar. Height of rocket-shaped precipitin band
proportional to concentration of ag.Proteins separated by electrophoresis then double diffusion
with reagent abs in trough in agar. Shape, intensity, & loca-
tion of precipitin arcs compared with normal control.Proteins separated by electrophoresis. Antiserum placed
directly on gel. Ag-ab complexes precipitate.Light scattering by ag-ab complexes.APPLICATION
See examples below.Fungal antigens, extractable nuclear
antigens.No longer commonly performed except
for low-volume testing of IgD & IgG.Igs, complement, alpha-fetoprotein.Serum proteins, including Igs. Largely
replaced by immunofixation elec-
trophoresis.ID of Igs in monoclonal gammopathies,
Bence Jones proteins. Western blot is an
adaptation.Igs, complement, C-reactive protein.