HYPERSENSITIVITY,HYPERSENSITIVITY, Educational Platform

2. HYPERSENSITIVITY
Imran Yousafzai
BSN(Pak), MSPH(Pak), PGHRHM(UK),
MHPE(Pak)

3. Objectives
At the completion of this session learners would be able to:
• review the following concepts of immune response
– Components of immune response
– Humoral versus cell mediated immunity
– Antigen processing ,presentation and recognition
• discuss the disorder of immune response i.e. Hypersensitivity
( allergies)
– Immediate and delayed hypersensitivity
• discuss the pathophysiology of different types of
hypersensitivity (Type I, Type II, Type III & Type IV)

4. Hypersensivity
What do you know about hypersensitivity?

5. Immunity
• Immunity is the body's ability to fight off harmful
microorganisms (Pathogens) that invade it.
• The immune system produces antibodies or cells
that can deactivate pathogens.
• Fungi, protozoans, bacteria, and viruses are all
potential pathogens.

6. Types of immunity
• There are three types of immunity
1) Innate immunity
2) Active immunity
3) Passive immunity

7. Innate immunity:
• It is inborn or natural immunity. One may inherit
some form of immunity from his or her mother milk.
This is the innate immunity.
• For example resistance of skin to the invasion by
bacteria, destruction of germs in the stomach by its
acidic secretion & enzymes and phagocytosis of
bacteria and other invaders by WBCs.

8. Active Immunity
• Active Immunity occurs when one makes his/her
own antibodies. This type of immunity is long term.
It has two subtypes
– Naturally-Acquired Active Immunity: If you get
an infectious disease (like VARICELLA), often
times, that stimulates the production of MEMORY
cells which are then stored to prevent the
infection in the future.
– Artificially-Acquired Active Immunity: Injecting or
taking antigens by mouth. Takes time for T and B
cells to be activated but gives long lasting
immunity.

9. Passive Immunity
• Passive Immunity occurs when the antibodies come
from some other source. This type of immunity is
short term.
• It has further divided in to two types.
– Natural passive: Mother to child through placenta
or milk.
– Artificial passive: Used during potentially fatal
diseases. Provides an instant response but only
temporary as antibodies are not the body's own
so memory cells are not created. E.g. tetanus -
injection of antitoxins given.

10. Hypersensitivity refers to undesirable
(damaging, discomfort-producing and
sometimes fatal) reactions produced by
the normal immune system.
OR
‘over reaction’ of the immune system to
harmless environmental antigens

11. Types of hypersensitivity
reactions
Type I: immediate hypersensitivity
Type II: cytotoxic hypersensitivity
Type III: Immune complex –type
hypersensitivity
Type IV: cell mediated hypersensitivity
or Delayed-type hypersensitivity

12. Type I hypersensitivity (allergy)
• Occur and disappear rapidly
• The major problem is functional disorder
almost without tissue injury
• Prerequisite: need prior sensitization to antigen
• Mediated by Ig E antibody
• Bear an individual difference: atopic families
are susceptible to allergic disease
• Rapid liberation of active chemicals such as
histamine and serotonin

13. Triggers
• Food – peanuts
• Insects – bee sting
• Drugs/Chemicals – penicillin
• Animal Dander – cat
• Dust – mites
• Plant Pollen
• Mold Spores – penicillium

14. The major components and cells participating
in Type I hypersensitivity
1. Allergens
2. Allergins: IgE
3. Mast cells and basophil
4. Eosinophil

15. Allergens

16. Mechanism of type I hypersensitivity
1. Allergy-induced period
2. allergy-stimulated period
3. effector period

17. Allergy-induced period
Allergen
Production of Ig E
IgE binds to mast cells and basophils

18. Tissue Affected
The tissues most commonly affected are the skin, the
respiratory tract and the alimentary tract. The results
are at best uncomfortable (e.g. hay fever, eczema, food
allergy) at worst fatal (asthma, anaphylaxis)

19. Comparison of normal bronchiole to asthmatic bronchiole

20. • Symptoms of systemic anaphylactic

21. Type II
• Type II hypersensitivity is also known as
cytotoxic hypersensitivity and may affect a
variety of organs and tissues.

22. Type 2 Hypersensitivity reaction
• In this condition IgG or IgM antibodies are formed
which react with surface proteins of the bodies
own cells. The result in complement-mediated
lysis of the cells
• Examples:
• Hemolytic disease of the new born (Rhesus disease)
where lgG antibodies transferred from the mother
lyse the babies cells
• Rare, but serious, are cases where drugs or their
metabolites bind to red cell or platelet membranes
and induce antibody formation. This is found as a
sporadic reaction with a range of drugs

23. Examples:Type II
• Drug-induced hemolytic anemia,
granulocytopeniaDrug-induced hemolytic
anemia, granulocytopenia and
thrombocytopenia are such examples. The
reaction time is minutes to hours.
• Hemolytic disease of the new born (Rhesus
disease) where lgG antibodies transferred
from the mother lyse the babies cells

24. Hemolytic disease of the new born
1st Pregnancy
is normal Subsequent
Pregnancy baby

25. And the result

26. Type III Hypersensitivity
• Type III hypersensitivity is also known as immune
complex hypersensitivity (IgG & IgM).
• The reaction may be general (e.g., serum sickness) or
may involve individual organs including skin (e.g.,
systemic lupus erythematosus), joints (e.g.,
rheumatoid arthritis) or other organs.

27. Type IV Hypersensitivity
• Type IV hypersensitivity is also known as cell
mediated or delayed type hypersensitivity.
• The classical example of this hypersensitivity is
tuberculin (Montoux) reaction which peaks 48 hours
after the injection of antigen (PPD or old tuberculin).
• The lesion is characterized by indurationThe lesion is
characterized by induration and erythema.

28. Tuberculin Test