Counter Immunoelectrophoresis (CIE) Basics

Counter Immunoelectrophoresis (CIE)

• CIE is a laboratory technique used to detect the binding of an antibody to its specific antigen.
• An electric field is applied to accelerate the migration of antigens and antibodies in a gel medium (typically agar).
• The rapid movement of antibody and antigen causes them to meet and form a precipitation line.

Principle of CIE

• CIE relies on the movement of charged molecules. Strongly negatively charged antigens move towards the anode, while antibodies move towards the cathode.
• The test is performed on a glass slide with agarose gel. Two wells are punched out. One well holds the antigen, the other holds the antibody.
• An electric current is applied causing rapid migration.
• A visible precipitation line (precipitin arcs or lines) forms within 30-60 minutes, indicating a positive reaction.

Interpretation of Results

• A precipitin line between the antigen and antisera wells signifies a positive reaction, indicating a specific antigen-antibody reaction. (Specificity)
• The absence of these lines may indicate no reaction or the lack of a particular antibody for the antigen. (Non-specificity)
• Multiple precipitin lines suggest heterogeneity of the antibody reacting with the antigen.

Advantages and Limitations of CIE

• Advantages: Faster and more sensitive than double immunodiffusion (takes ~30 minutes).
• Limitations: More expensive than agglutination-based tests. Potentially lower sensitivity, speed, and simplicity compared to latex agglutination. Requires a larger quantity of antigen and antibody.

Uses of CIE

• Detects antigens and antibodies in serum, cerebrospinal fluid, and other bodily fluids to diagnose various infectious diseases (e.g., bacterial, viral, fungal, parasitic).
• Used for detecting Hepatitis B surface antigen (HBsAg), fetoprotein, hydatid, and amoebic antigens.
• Used for detecting pneumococcal capsular antigens in sputum.