Agglutination
The interaction between antigen and antibody is called antigen-antibody interaction, Agglutination test refers to the examination of clump formation when particulate antigen and its antibody are combined
• The antibody binds with the antigen to form a complex molecule called immune complex or variable reagent
• This reaction is specific in nature (ex: lens antigen)
• The part of the antibody which combines with antigenis called paratope or antigen binding site
The part of the antigen which combines with the antibody is called epitope or antigenic determinant
Agglutination happens when there is a reaction between antigen and antibody
• Agglutination : It is defined as the interaction between antibody and a particulate antigen which results in clumping
•The antibodies that produce such reactions are called as agglutinins
• The particulate antigens aggregated are called agglutinogens
Response effect
• Excess antibody has got the capacity to inhibit the agglutination reaction
• As the antibody concentration is lowered below the responce, the reaction occurs.
MECHANISM
• Primary phenomenon (SENSITIZATION)
First reaction involving Ag-Ab combination Single antigenic determinant on the surface particle
1) Initial reaction: rapid and reversible
2) Cross link formation -
visible aggregates (stabilization)
______________________
APPLICATIONS OF AGGLUTINATION TEST
1. ABO blood grouping
2. Rh blood grouping
3. Widal test for typhoid
4. Weil felix test for typhus
5. Coomb's test for the identification of anti Rh antibodies
6. Brucella agglutination test for brucellosis
7. Leptospira agglutionarion for leptospirosis
8. Cold agglutination test for pneumonia, malaria and trypanosomiasis
9. Haemagglutination inhibition test for the diagnosis of certain viral and parasitic diseases
__________________2
Latex agglutination inhibition
The latex agglutination inhibition test was also developed in the early 1960s. It used polystyrene latex particles coated with hCG. A mixture of centrifuged human urine and rabbit hCG anti-serum was prepared and added to the hCG coated latex particle suspension. If the urine was free of hCG, the latex particles would agglutinate in response to the rabbit hCG anti-serum. If hCG was present in the urine, the hCG would neutralise the rabbit hCG anti-serum and agglutination of the latex particles would not occur.
KIT REAGENTS
_____________________3
Radioimmunoassay
Radioimmunoassay (RIA) is a very sensitive in vitro assay technique used to measure concentrations of antigens (for example, hormone levels in the blood) by use of antibodies.
RIA technique is extremely sensitive and extremely specific, requiring specialized equipment, it remains the least expensive method to perform such tests.
Method
1. To perform a radioimmunoassay, a known quantity of an antigen is made radioactive, frequently by labeling it with gammaradioactive isotopes of iodine attached to tyrosine (hot).
2. This radiolabeled antigen is then mixed with a known amount of antibody
for that antigen, and as a result, the two specifically bind to one another. 3. Then, a sample of serum from a patient containing an unknown quantity of that same antigen is added.
4. This causes the unlabeled (or "cold") antigen from the serum to compete with the radiolabeled antigen ("hot") for antibody binding sites.
____________________
Precipitation and immunodiffusion in gels
Based on different rates of diffusion of Ag and Ab into the gel, depending on their:
- concentration
- physicochemical properties
- gel structure
Most widely used gels - agar agarose Tests are performed by pouring molten 1 agar (agarose) onto glass slides.
Single (simple) diffusion in one dimension: - The process of diffusion of an antigen in an antibody-containing gel
- The process of diffusion of an antibody in an antigen-containing gel.
Double diffusion in two dimensions
تعليقات
إرسال تعليق