The document discusses various types of antigen-antibody reactions: 1) Precipitation reactions occur when antigen is mixed with antibodies. 2) Agglutination reactions cause particulate antigens to clump together when mixed with antibodies in the presence of electrolytes. Common examples are blood grouping and detection of typhoid. 3) Neutralization reactions involve antitoxins neutralizing toxins. Examples include toxigenicity tests and the Schick test.

1. ANTIGEN AND ANTIBODY
MAN BAHADUR RANA
BPH
ACAS,NEPAL

3. Types of Antigen – Antibody Reaction:
• Precipitation Reaction.
• Agglutination Reaction.
• Complement Fixation.
•Neutralisation Reaction
• ELISA – Enzyme Linked ImmunoSorbent Assay.
• Immunofluorescence.
•Radioimmunoassay
The types of antigen – antibody reactions are:

4. Precipitation Reaction:

5. Antigen Added

7. Agglutination Reaction:
• When a particular Ag is mixed with its Ab’s in the
presence of electrolytes at a suitable temperature and
pH, the particles are clumped or agglutinated.
• The Ab of the serum causes the cellular Ag’s to form
clumps and these are called Agglutinins.
• The particulate antigens that are aggregated are
termed Agglutinogens.
 Slide agglutination: This is a rapid method to
determine the presence of agglutinating antibodies.
This test is used for blood grouping
(Haemagglutination) and cross matching.

8. Tube agglutination:
Tube agglutination is employed for the serological
diagnosis of typhoid, brucellosis and typhus fever.
Widal test is used for the estimation of typhoid fever.

9. •antitoxin + toxin  neutralization
•toxigenecity test
•Shick test
•Nagler reaction
Neutralisation Reaction

10. Complement Fixation:
•This complement system 11 proteins
•Fc component of Ag-Ab complex.
•E.g wasserman reaction
•Immobilisation test for T. pallidium

12.  Radioimmunoassay (RIA)  in vitro assay  concentrations
of antigens (for example, hormone levels in theblood) by use of
antibodies.
Principle:
RIA relies on the radioactivity of a specific isotope labelled antibody or
antigen
Application
circulation proteins, hormones and drugs
INTRODUCTION
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13. Solid phase radioimmunoassay
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14. Immunofluorescence utilizes fluorescent-
labeled antibodies to detect specific target
antigens. It is used widely in both scientific
research and clinical laboratories.
Coons et al (1942) labeled dyes can be conjugated
to Ab’s and these labeled antibodies can be used to
detect Ag’s.
•Fluorescein, Phycoerythrin.
Immunofluorescence:

16. INTRODUCTION TO ELISA
 ELISA, or enzyme-linked immunosorbent
assay, quantitative immunological Ag- Ab
reaction is monitored by enzyme
measurements.
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