What are the 3 types of immune systems? These specialized cells and parts of the immune system offer the body protection against disease. This protection is called immunity. Humans have three types of immunity — innate, adaptive, and passive: Innate immunity: Everyone is born with innate (or natural) immunity, a type of general protection.

1. Antigen-Antibody Reactions
Part 1

2. Intended Learning Outcomes
•Define antigen antibody reactions.
•List different types of antigen
antibody reactions.
•State the conditions for agglutination
to occur with examples.
•Interpret the results of the provided
agglutination tests.

3. It’s the reaction that occurs when an antigen
combines with its specific antibody to produce
an immune complex
What is an antigen antibody reaction
(Serological Reaction)?
Ab
In vitro tests that detect formed immune complexes
Serological tests
Ag

4. If you have a specific antigen ‘’x’’ for an
organism:
•Can you use it to search for antigen-specific
antibodies in patient’s serum?
•Can you use the antigen-specific antibody to
search for antigen ‘’x’’?

5. Antigen Antibody Reactions
Agglutination
Neutralization
Precipitation
Radioimmunoassay
Enzyme-Linked
Immunosorbent Assay
Immunofluorescence

6. Agglutination = Visible clumping
Agglutinogen
Agglutinin
+ =
Agglutination
I. Agglutination Reaction

7. Antigenic particles are
cross-linked
to each other by antibodies
Large lattice of
Ag-Ab complex
Visible Deposit
(Clumps)
+

8. Agglutination
Direct (Active)
Agglutination
Indirect (Passive)
Agglutination
 The antigen is large &
insoluble (Particulate)
 The antigen is small &
soluble
 Must be adsorbed to
insoluble inert particle to
allow visible
agglutination reaction

10. • Identification and typing of pathogens.
• Blood grouping.
Direct Agglutination
Slide Agglutination Test
Qualitative
detection of
antigen

11. Measure the level of serum antibody
against antigen (Quantitative detection).
Serial dilution
of the patient
serum
Add fixed
amount
of antigen
Pro-zone
phenomenon?
Direct Agglutination
Tube Agglutination Test

12. Direct Agglutination
Tube Agglutination Test

13. Prozone
phenomenon
High Ab/Ag
ratio
How to overcome?
1. Wide range of
serial dilution
2. Add Coomb’s
factor

14. Agglutination
Direct
Agglutination
Passive (Indirect)
Agglutination
Remember
Slide
Agglutination
Tube
Agglutination
Qualitative
Ag detection
Quantitative
Ab detection

15. Passive (Indirect) Agglutination tests
Adsorptions of soluble
antigen to an insoluble
inert particle
Latex
agglutination
Hemagglutination Coagglutination
L
Latex particles
Erythrocytes Staphylococci
(Strains With
surface Protein A)

16. It’s the detection of antibodies against soluble
Ag as bacterial toxins & enzymes.
Passive Latex Agglutination
Visible Agglutination
e.g. Anti-streptolysin O test
+
Patient’s serum
No Agglutination

18. +
Reverse Passive Latex Agglutination
 We use latex particles to search for antigen
instead of antibodies.
 Examples:
 Detection of Lancefield Group A & B Streptococcal
antigen
 Detection of pregnancy hormone

19. Click to edit Master title style
• Edit Master text styles
• Second level
• Third level
• Fourth level
• Fifth level
What is Hemeagglutination?
Agglutination reaction when the
antigen is an erythrocyte

20. Hemagglutination
Coat erythrocytes with
Ag  Passive
hemagglutination
Ab  Reverse passive
hemagglutination

21. Application : Coombs’ test
Direct Coomb’s test
measures antibody
bound to the red
blood cells (RBCs) in
the patient
Indirect Coomb’s test
measures free antibody in
the serum of the patient

22. Direct Coombs’ test

23. Indirect Coombs’ test

24. Co-agglutination

25. Subgroup Activity
Discussion groups

26. Thank You!