immunological action in living beings

1. Antigen –Antibody
Reaction
Abhishek Routray

2. Points to focus on……………………….
• Introduction
• Stages of reaction
• General features of the reaction
• Measurement of the reaction

3. INTRODUCTION

4. • In the body they form antibody mediated immunity.
• In laboratory they help in diagnosis of infections.
• In epidemiological surveys it differentiates the infectious from the non infectious one and screen the population
for particular infection.
• In general these reaction can be used for detection and quantitation of either antigen and antibody

5. Antigen antibody reaction in vitro is known as serological reaction

6. STAGES

7. stages
primary
secondary
tertiary

8. Primary stages Secondary stages Tertiary stages
Initial reaction rapid Visible effect Neutralization and destruction of
infectious agent or tissue
damage
Reversible Precipitation Involves humoral immunity
against infectious diseases as
well as clinical allergy.
No visible effect agglutination
Weak intermolecular bond Neutralization of toxin
Detected by estimating bound
Ag & Ab and other method llike
 Radioactive isotope
 Fluroscent dyes
 ferritin
Complement
fixation,Immbolizaation of
motile organism

9. General features

10. • Reaction is specific.
• Entire molecule not fragment reacts.
• No denaturation of the antigen on the antibody during reaction.
• The combination occurs at the surface,firm but reversible.
avidity affinity
Strength of bond after formation of
Ag-Ab complex
Describe intensity of interaction of Ag-
Ab complex
It is the function of closeness of fit
between the epitope and antigen
binding region of its antibody

11. • Both antigen and antibody participates in the formation of agglutinates
• Antigen antibody can combine in varying proportion unlike chemicals with
fixed valency
• Both antigens and antibodies are multivalent and antibodies are generally
bivalent

12. MEASUREMENT OF ANTIGEN AND
ANTIBODY

13. Measurement Is in the term of mass or unit or titre.
Antibody titre of the serum is the highest dilution of serum which shows an observable reaction
with antigen
sensitivity
• The ability of test to detect even minute
quantity of antigen and antibody
• When the test is highly sensitive false negative
result may be absent or minimal
specificity
• ability of the test to detect homologus antigen
and antibody
• In highly specific test false positive reactions
are absent or minimal.

14. In generally sensitivity and specificity of a test is in inverse proportion