Lecture 18: Hypersensitivity Reactions

Question 1

Type I hypersensitvity is mediated by

Answer 1

IgE and results from the actions of mediators secreted by the mast cells

Question 2

Type II hypersensitvity is mediated by

Answer 2

Abs that bind tissue Ags and cause complement-dependent tissue injury and disease

Question 3

Type III hypersensitivity is mediated by

Answer 3

Abs that bind to circulating Ags to form immune complexes, which deposit in vessels and cause complement-dependent injury in the vessel wall (vasulitis)

Question 4

Type IV hypersensitivity is mediated by

Answer 4

T cells and results from inflammation caused by cytokines produced by CD4+ Th1 and Th17 cells, or killing of host cells by CD8+ CTLs

Question 5

____ refers to the genetic tendency to develop allergic diseases.

Answer 5

Atopy (individuals with a strong propensity to develop allergic reactions are said to be atopic)

Question 6

The Seqeunce of events in the development of immediate hypersensitivity reactions

Answer 6

Question 7

difference between immediate and late phase of Type I hypersensitivity

Answer 7

• The immediate vascular and smooth muscle reaction to allergen develops within minutes
  
  • Morphology of the immediate reaction is characterized by
    
    • vasodilation
    • congestion
    • edema
• The late-phase reaction develops 2-24 hours later
  
  • characterized by:
    
    • inflammatory infiltrate rich eosinophils, neutrophils, and T cells

Question 8

Characteristics of asthma and bronchospasms

Answer 8

• Local reaction
• Inflammatory mediators cause the loosening of tight junctions in the bronchiole epithelium, increased capillary permeability, and spasmatic contraction of smooth muscle surrounding bronchi
  
  • this temporarily decreases the size fo the bronchial lumen, resulting in shortness of breath

Question 9

Anaphylaxis

Answer 9

• Systemic reaction
• exposure to allergen may cause the rapid release of vasoactive amines from mast cells and basophils as well as a flood of cytokines, resulting in the contraction of smooth muscle in the vasculature and vasodilation of capillary endothelium
• blood pressure decreases, resulting in vascular shock
• in addition, the release of mediators increases the contraction of smooth muscles in the bronchi and bronchioles of the respiratory tract, making breathing difficult

Question 10

alleren testing assess Type ____ hypersensitivities to various potential allergens

Answer 10

Type I hypersensitivities (positive reactions are indicated as redness and swelling within 20 to 30 minutes after exposure to the allergen)

Question 11

Effector mechanisms of Type II hypersensitivity

Answer 11

Question 12

Diseases of Type II Hypersensitivity

Answer 12

Question 13

Diseases of Type III hypersensitivity

Answer 13

Question 14

Diseases of Type IV Hypersensitivity

Answer 14

Question 15

Tissue injury from Type IV hypersensitivity (delayed-type Hypersensitivity (DTH))

Answer 15

• Tissue injury results from the products of the recruited and activated neutrophils and macrophages, such as lysosomal enzymes, reactive oxygen species, nitric oxide, and proinflammatory cytokines

Question 16

Granulomas contain

Answer 16

• activated macrophages, multinucleated giant cells, and lymphocytes (primarily T cells)
• (caused by TB escaping the macrophage and causing it to go crazy)

Question 17

Function of leukotrienes

Answer 17

Stimulate prolonged smooth muscle dilation

Question 18

Question 19

Question 20

The classical T cell-mediated inflammatory reaction is called _______

Answer 20

delayed-type hypersensitivity (DTH)

Question 21

In a delayed-type hypersensitivity (DTH) reaction what are the makure cells that secrete cytokines and recuruite/activate leukocytes

Answer 21

Th1 and Th17

Question 22

Question 23

Contact dermatitis is an example of what type of hypersensitivity

Answer 23

Type IV (delayed hypersensitivity)

Question 24

Formation of a mature granuloma

Answer 24

• Within hours to days after Ag exposure, Activated Th1 cells home ot the tissue
• If the source of Ags is not eradicated, inflammation will persist
• Th1 Cd4+ T cells and activated Macrophages by IFN-gamma which leads to production of TNF
• IFN-gamma and TNF further stimulate macrophages
• Over the course of several days to weeks a mature granuloma is formed

Question 25

Question 26

Principles of immunotherapy

Answer 26

Question 27

Question 28

What is the principle diagnostic test for systemic lupus erythrematosus

Answer 28

Anti-nuclear Abs

Question 29

Question 30

Question 31