Antigen-Antibody Interaction or Antigen-Antibody Raction (Serological Reaction
The serum contains antibodies, so the antigen-antibody reaction occuring in serum is known serological reaction.
When antigen enters in human body through infection or artificial means (vaccine; it stimulates antibody production)
After that reaction occurs between antigen and antibodies in two main stages;
1. Primary stage is the initial interaction between antigen- antibody, without any visible effects.
2. Secondary stage leads to visible effects event such as;
Precipitation
Agglutination
Killing of living antigens
Lysis of cell
Neutralization of toxins
Enhancement of phagocytosis
Complement fixation
Such reaction are useful in laboratory diagnosis of various disease and in identification of infectious agent in epidemiological survey.
General features of antigen- antibody reaction
1. Reaction is highly specific
2. Antigen-antibody molecules held together in lock and key arrangement
3. Both antigen antibody participate in reaction.
4. Ag and Ab may combine in varying proportions
5. Entire molecules of antigen and antibody interact during during combination
6. Both Ag and Ab participate in formation of agglutinates or precipitates.
7. No denaturation of antigen or antibody occuring the reaction
8. The combination is firm (strong) but reversible.
(Intensity of attraction between antigen and antibody molecules).
Strength of bond after formation of antigen- antibody complex.
9. For example;
Widal test
VDRL test
Comes under serological reaction.
Major Serological Reactions
Major serological reactions are;
Serological Reaction
1. Precipitation reaction
2. Agglutination reaction
3. Complement fixation test
4. Immunofluorescence reaction
5. Neutralization test
6. Radioimmunoassay (RIA)
7. ELISA (Enzyme Linked Immunosorbent Assay)
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