An introductory presentation for undergraduate medical students on antigens and antibodies, immunoglobulins, primary and secondary antibody responses, active and passive immunity

1. Maj Muhammad Omair Riaz
MBBS, FCPS (Immunology)
Consultant Immunologist

2. Should be able to:
 Define antigen
 List the factors which determine the
immunogenicity of an antigen
 Enumerate differences between Active and
passive immunity
 Give an overview of primary & secondary antibody
responses
 Describe the types of Immunoglobulins

3.  Review of Medical Microbiology &
Immunology, byWarren Levinson
 Chapter 59
 Chapter 60
 And

4. Don’t
 Talk
 Day dream
 Whatsapp
 Take pictures
 Sleep
Infact, you can.. As long as you pretend that
you are listening!

5. Immunology is an invention of the devil, who is
making it up as he goes along because he's not
too clear about this
stuff either.
-Janice H Tanne, 1990

6.  A study of normal immune response & the
diseases due to it’s defects

7. “ a reaction to antigens, including components
of microbes as well as to macromolecules, such
as proteins and polysaccharides, and small
chemicals that are recognized as foreign,
….regardless of the physiologic or pathologic
consequence of such a reaction “

8.  Antibody Generator
 Not all antigens generate antibodies!!!
 Those that generate antibodies are called
Immunogens
 Antigens are recognized by being
“different”

9. T & B cells are tolerant to antigens exposed to them during their
development. Later on they learn to recognize “different” antigens

11. Antigen specific immune responses are generated byT & B Cells

12. Human B cells can produce antibodies against 10 million possible antigens

13.  Difference between
self and non-self
 Self recognizable by
MHC

14.  Foreignness
 Recognized as self are not immunogenic
 Molecular size
 Higher the weight, greater the immunogenicity
 Complexity
 Epitopes
 Dosage, route & timing

15.  The small pox … story!

16.  Smallpox is a
contagious, disfiguring
and often deadly
disease that had
affected humans for
thousands of years!

21. ACTIVE IMMUNITY
 Long duration
 Slow onset
 Takes time to
develop
 Antibodies &T cells
produced in the host
 Example:
 Infections
PASSIVE IMMUNITY
 Short duration
 Rapid onset
 Ready for action
 Preformed antibodies
transferred to patient
 Example:
 Vaccines

22.  Antibodies are immunoglobulins!!
 Y shaped protein
 Produced by B Cells after encountering an antigen
 Circulate in blood
 Neutralize bacteria, viruses etc

23. Immune globulins
“in response to
an antigen”
“Spherical, globe-like
proteins”

27.  IgG
 IgA
 IgM
 IgE
 IgD

29.  Two L chain &Two H chains, Divalent
 Four subclasses (IgG1, IgG2, IgG3, IgG4)
 Important in secondary immune response
 Can cross placenta
 Most abundant immunoglobulin in the
body
 Opsonizing antibody (Binds to its heavy
chain receptors on phagocyte cell surface
to allow phagocytosis)

30.  A pentamer of 2 heavy & 2 light chains
 Decavalent
 No subtype
 Most efficient Ig in Ag-Ab reactions
 Because it has 10 binding sites!!!
 Important in primary immune responses
 All rapid tests are based on it
 Dengue,Typhidot, HCV, HBV

31.  Monomer/ dimer
 Present in secretions
 Saliva
 Tears
 Epithelial secretions (Respiratory, Genitourinary,
gut)

32.  Imp for 2 reasons
 Allergy
 Immune response against parasites
 Only in trace amounts in serum
 Increased in allergic patients

33.  No known function
 Still an enigma…!
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3048779/

36.  IgG was the first Gamma globulin to be
discovered , ..Hence the IgG
 IgM was the “bigger” globulin, the
Macroglobulin.. Hence the IgM
 When they discovered the third
Immunoglobulin, they said.. let’s get it
straight now.. Let’s start from A… Hence The
IgA

37.  And then someone discovered yet ANOTHER
immunoglobulin.
 While looking for a name, their first choice
was IgB but at that time it was expected that
Igs in mice would be called β-globulins
 The Roman letter ‘C’ has no Greek equivalent.
 Thus, left with little choice but to name the
new class of antibody IgD.

40.  A medical student at CMH LMC was admitted
to CMH with suspicion of Dengue fever. A
Dengue rapid test shows that [ IgM-
Negative, IgG- Positive]. What’s the
diagnosis?
 Past dengue infection!

42.  Factors which increase immunogenicity of an
antigen include all, except:
 Foreignness
 Complexity
 Low molecular weight
 Recognition as Non-self

43.  Factors which increase immunogenicity of an
antigen include all, except:
 Foreignness
 Complexity
 Low molecular weight
 Recognition as Non-self
 High molecular weight makes the antigen more
immunogenic

44.  All of the following is true for active
immunity, except:
 It has a longer duration
 It has a slower onset
 Antibodies &T cells are produced in the host
 An example of active immunity is vaccines

45.  All of the following is true for active
immunity, except:
 It has a longer duration
 It has a slower onset
 Antibodies &T cells are produced in the host
 An example of active immunity is vaccines
 Vaccines are PASSIVE immunity

46.  Which immunoglobulin is implicated in
primary antibody response?
 IgG
 IgA
 IgM
 IgD
 IgE

47.  Which immunoglobulin is implicated in
primary antibody response?
 IgG
 IgA
 IgM
 IgD
 IgE

48.  How many types of Immunoglobulins are
there?
 4
 100, 1253,697 (100 million +)
 Five
 Sorry,..What… I was busy whatsapping!
 #$%@^ Why is it even important??

49.  How many types of Immunoglobulins are
there?
 4
 100, 1253,697 (100 million +)
 Five
 Sorry,..What… I was busy whatsapping!
 #$%@^ Why is it even important??
 Total 5, clinically relevant 4, 100 million plus are
present in body at any one time

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