Immunology Project

1. Hypersensitivity and Allergy
Dalya Al-Soos|Shahad Al-Awad
Biology and Biotechnology
Thamer Hamdan ,PhD
American University of Madaba

2. Definition
• Hypersensitivity: An excessive immune triggered by a harmless antigen,
causes damage to host.
• Allergy: An environmental antigen causes a hypersensitivity response.
• Allergens: An inhaled or eaten substance, causes an allergic reaction
when recognized by the immune system.
• Atopy: The genetic tendency to predisposition for developing allergic
diseases.

3. Allergen
• Natural Environment:
1. Pollen
2. House dust mites
3. Bacteria
4. House pets epidermis
5. Mold fungi spores
• Chemically contaminated environment:
1. food product additives,
2. Latex
3. Drugs
4. Metals
5. Aldehydes (perfumes,….)

4. Hypersensitivity
Type 1
• IgE
Mediated
• Classic
Allergy
Type 2
• IgG/IgM
Mediated
• RBC
Lysis
Type 3
• IgG
Mediated
• Immune
complex
Type 4
• T Cell
• Delayed
type

5. Type 1 Hypersensitivity
• Atopy:
1. predisposition to type 1 hypersensitivity
2. Higher levels of circulating IgE, which will be attached to mast cells
3. Great amount of Eosinophils.
• Allergens:
1. pollen
2. mites
3. foods
4. drugs
5. insect venoms

6. Sensitization

7. Type 1 Hypersensitivity (Cont.)
• Mechanism Response:

9. Mast Cell Degranulation
1. Leukotrienes
2. platelet activating factor
3. Histamine
4. Cytokines
5. Chemokines

10. Mast Cell Receptors
1. Fc epsilon RI
2. Alpha chain
3. Gamma chain
4. Cross linkage activates PTKs

11. Type 1 Hypersensitivity Symptoms
1. Asthma
2. Systemic Anaphylaxis
3. allergic rhinitis (hay fever)
4. Ocular allergic conjunctivitis
5. Dermatological hives, atopic eczema, or erythema
6. Soft tissue angioedema
7. Pulmonary reactions

12. Prausnitz-Küstner reaction
Its a serum injected to test if
the body has
immunoglobulin E activity
in the skin, it includes
swelling, produced by the
release of serum into the
tissues (wheal), and redness
of the skin, resulting from
the dilation of blood vessels
(flare).

14. Type II hypersensitivity
1. Opsonization and complement- Fc receptor mediated phagocytosis
2. Complement- and Fc receptor-mediated inflammation
3. Antibody-mediated cellular dysfunction

15. Type II hypersensitivity (Cont.)

16. Type II hypersensitivity (Cont.)

17. Type II hypersensitivity (Cont.)

18. Non-autoimmune type II reactions
1. Transfusion reactions (ABO incompatibility)

19. Non-autoimmune type II reactions (Cont.)
2. Hemolytic disease of the newborn (erythroblastosis fetalis)

20. Type III Hypersensitivity
Immune Complex Disease
• Reaction with antigen and antibodies create immune complexes.
• The complexes get deposited in tissues:
- Localized reaction is when they are deposited near the site of antigen entry
- When formed in the blood reaction can develop where ever they are deposited
• Tissue is injured by the granular release from the neutrophil.

21. Mechanism of Type III Hypersensitivity Reaction

22. Localized Type III Reactions:
1. Injection of an antigen
2. Insect bite
Peaks at 4-8 hours Visible edema
Severe hemorrhage Can be
followed by ulceration

23. Generalized Type III Reactions:
Serum Sickness-type III hypersensitivity
- Reaction that develops when antigen is intravenously administered resulting in
formation of large amounts antigen-antibody complexes and the deposition in tissue.
Other conditions caused by Type III- Hypersensitivity
1. Infectious Diseases
- Meningitis
- Hepatitis
- Mononucleosis
2. Drug Reactions
- Allergies to penicillin and sulfonamides
3. Autoimmune Diseases
- Systematic lupus erythematosus
- Rheumatoid arthritis

24. Systematic lupus erythematosus
)Autoimmune Diseases(
Rheumatoid arthritis
)Autoimmune Diseases(
Mononucleosis ) Infectious Diseases(
Allergies to penicillin and
sulfonamides) Drug Reactions(

25. Type IV Hypersensitivity
Delayed type (T- cell mediated)
“DTH”
• What is delayed type hypersensitivity (DTH)?
- Response mediated by sensitized TDTH cells.
• Generally occurs 2-3 days after TDTH cells interact with
antigen.
• Examples:
- The tuberculin reaction
- Contact dermatitis

26. Tissue Injury and Cell Death Mechanisms

27. Phases of the DTH Response Stage
Sensitization stage:
- Occurs 1-2 weeks after primary contact with Ag.
What happens during this stage?

28. Phases of the DTH Response Stage
Effector phase:
- Occurs upon subsequent exposure to the Ag.
What happens during this phase?

29. Contact dermatitis (Type IV DTH )

30. Contact Dermatitis (A Type IV Reaction)
• Blistering skin lesions on hand of patient
with poison ivy

31. Tuberculin-type Reaction

32. Granuloma development from DTH
Mediated by Chronic Inflammation

33. How Important is the DTH Response?
• The AIDS virus illustrates the vitally important role of the DTH response in protecting
against various intracellular pathogens.
• The disease cause severe depletion of CD4+ T cells, which results in a loss of the DTH
response.
• AIDS patients develop life-threatening infections from intracellular pathogens that
normally would not occur in individuals with intact DTH responses.

34. Questions?
Thank you 