Hypersensitivity

Question 1

Hypersensitivity Definition

Answer 1

Hyperactive immune responses against “harmless” antigens

Question 2

Hypersensitivity 1: The allergic Reaction

Answer 2

Immediate Reaction to allergen: MAST CELLS AND BASOPHILS

Late Phase Reaction: Caused by mediators released, they recruit inflammatory cells such as EOSINOPHILS AND NEUTROPHILS

Question 3

Mediators of Type I Hypersensitivity

Answer 3

• Histamine:
  
  • Vasodilation
  • Increased capillary permeability
  • Smooth muscle contraction (bronchospasm)
• Prostaglandins
  
  • Bronchoconstriction
• Leukotrienes
  
  • Capillary permeability
• TNF-a, IL-4
  
  • Inflammation

Question 4

Allergen Definition

Answer 4

Small inhaled proteins that stimulate IgE production in atopic (tendency to develop allergy) individuals

Question 5

Effective Allergen Traits

Answer 5

• Small, highly soluble
• Low dose
• Carried on dry particles (pollen)

Question 6

What is difference between non-atopic and atopic individuals?

Answer 6

Non-atopic: IgG Ab

Atopic: IgE Ab

Question 7

Hygiene hypothesis (childhood)

Answer 7

Early microbial infections important in biasing toward Th1 response to environmental allergens

Western hemisphere has better hygiene so less infections and therefore, more allergies.

Question 8

Why do some people have allergies?

Answer 8

• Th2 bias developed as a fetus
• Lack of childhood infection maintains Th2 bias
• Genetic predisposition towards allergies
• Lack of Tregulatory response to allergen

Question 9

Treatments for Allergies

Answer 9

• Bronchodilators (treats bronchoconstriction)
• Antihistamines (block histamine receptors)
• Corticosteroids (block cytokine production, therefore less Ab)
• Omalizumab (anitbody that blocks binding to mast cells, relieves symptoms and severity of asthma)
• Mast cell membrane stabilizers (prevents mast cell breakdown)
• Leukotriene modifiers (inhibits leukotriene)

Question 10

Only successful approach for CURE of allergy?

Answer 10

Specific Immunotherapy

Question 11

Types of Hypersensitivity Table

Answer 11

Question 12

Type II Hypersensitivity: Cytotoxic

Answer 12

Question 13

Type III: Immune Complex

Answer 13

Antigen-antibody complex induce inflammation in tissues

Persistant microbial or viral infections

Autoimmune disorders

Question 14

Type IV: Delayed

Answer 14

Macrophage ingests antigen, and presents an epitope on its surface with MHC II protein

Activates macrophages via Th1

Function of T-lymphocytes

Delayed: starts hours, days, after contact w antigen and lasts for days

Types: Contact hypersensitivity, Tuberculin-type

Question 15

Differences between types of hypersensitivity?

Answer 15

Types I, II, and III are ANTIBODY-mediated, while Type IV is cell-mediated (T) and delayed. Type I are mediated by IgE, whereas types II and III are mediated by IgG and involve complement.