Question

What is binding to the antibody in a agglutination reaction and in a precipitation reaction?

Answer 1

Agglutination reaction: When an insoluble (particulate) antigen is mixed with its antibody at a suitable temperature and pH, the particles are clumped or agglutinated.it is the fundamental reaction in the body by which the body is protected from complex foreign molecules,such as pathogens and their chemical toxins.The specificity of the binding is due to specific chemical constitution of each antibody. Applications: Slide agglutination:when a drop of the appropriate antiserum is added to a smooth ,uniform suspension of a particulate antigen in a drop of saline on a slide or tile,agglutination takes place.a positive result is indicated by the clumping together of the particles and the clearing of the drop.this method is used for blood grouping and cross matching.    

Precipitation reaction: When a soluble antigen combines with its antibody at a suitable temperature and pH, the antigen-antibody complex forms an insoluble precipitate in a reaction known as precipitation.when instead of setting the precipitate remains suspended as floccules,the reaction is known as flocculation.the amount of precipitate formed is determined by the relative amount of antigen and antibodies.if there is more antibody than antigen only weak precipitation reaction will occur called prozone effect.if there is more antigen than antibody only a weak reaction occurs,the amount of antigen and antibody is similar ,the largest reaction occurs,this is called zone of equivalence. Application: Ring test: This is the simplest type of precipitation test,it consists of layering the antigen solution over a column of antiserum in a narrow tube.a precipitate forms at the junction of the two liquid.ring test are used to group streptococci.