The principle of Counter Immunoelectrophoresis method is that at pH 8.4 the immunoglobulins will migrate to the negative end of a capillary system if an electric field has been applied to the capillary system. In the same capillary system, many antigens will migrate towards the positive end at that pH. As the antibody and antigen move towards each other in an electric field, they will soon meet in optimal proportion and visible precipitate is formed.
Salient features:
- Modification of the Ouchterlony method.
- Unknown bacterial antigen and a known specific antibody move towards each other in an electrical field
- Most bacterial antigen are negatively charged (eg. Capsular polysaccharide) in a slightly alkaline environment.
- When Ag and Ab meet in optimal proportions, a line of precipitation appear within the agar matrix
- The entire procedure takes about One hour.
- Any antigen for which antisera is available can be tested by CIE Sensivity less than that of particle agglutination (0.01-0.05 mg/ml) of antigen.
Uses of Counter Immunoelectrophoresis
Counter Immunoelectrophoresis is used to detect presence of capsular antigens in CSF of
- H. influenzae
- N. meningitidis
- S. Pneumoniae etc
Demerits of the test:
- CIE is more expensive than agglutination based tests.
- Initial capital outlay for the apparatus
- Need of large quantity of Ag and Ab
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