Hypersensitivity Reactions

Question 1

Which of the hypersensitivity reactions is Antibody Independent?

Answer 1

Type 4 Reaction

Question 2

What is the 1st exposure/priming of a Type 1 hypersensitivity reaction?

Answer 2

This is when a Dendritic Cell presents an allergen to a Th0 Cell–> Th2 CELL–> Activates B Cells–> Secrete Ig E

IgE will bind to the Mast cells through ERIIA receptors to release histamines during second response

**There are no free immune complexes present; IgE will be bound to the mast cell (mast cells are found in perivascular connective tissue)

Question 3

What is the 2nd exposure of a Type 2 hypersensitivity reaction like?

Answer 3

Allergen binds mast cells by IgE antibody for the second time. This results in a cascade of events which causes the release of:

• Neutrophil Chemotactic Factors
• Eosinophil Chemotactic Factors
• Proteases (to start complement cascade and results in tissue damage)
• Histamines: Vasodilation, increased permeability, glandular secretions

Question 4

How does asthma occur?

Answer 4

Type I hypersensitivity reaction that occurs from the activation of mast cells within the bronchioles

Results in:

1. ) Increased glandular secretion–> increased luminal obstruction via mucus
2. ) mucosal and submucosal swelling
3. ) Bronchioconstriction

Question 5

What are the strongest vasodilating signals in the Type I hypersensitivity reaction?

Answer 5

Leukotriene- C4, Leukotriene- D4, Leukotriene-E4

***STRONGEST VASODILATORS OF THE HUMAN BODY

Question 6

What are the diseases associated with Type I hypersensitivity reactions?

Answer 6

Localized Type I Hypersensitivity Reactions:
Allergic Reactions, Rhinitis, Angioedema, Hay Fever

Granulized Type I Hypersensitivity Reactions:
Anaphylactic Shock

Question 7

What is the key differentiating factor for Type 2 Hypersensitivity Reactions?

Answer 7

Antigen is always fixed and intrinsic to the tissue in which reaction occurs (IgG and IgM: “General Motors” Ab)

No free immune complexes

Question 8

What are some of the common diseases associated with Type 2 Hypersensitivity reactions?

Answer 8

Acute Rheumatic Fever, Glomerulonephritis, Myasthenia Gravis, Hyperthyroidism (Grave’s Disease), Hemolytic Anemia

Question 9

Mechanisms for these Type 2 Hypersensitivity Reactions?

Answer 9

Grave’s Disease/ Hyperthyroidism–> Ab binding to the TSH receptors will cause an increase in T3, T4 which will cause adaptive immune cells to attack and destroy these cells

Myasthenia Gravis–> attack of the immune cells by binding of Ab to the muscle receptors causing them to be the site of degradation!

Glomerulonephritis–> binding of complement antigens to the receptors of the glomerulus basement membrane makes these cells susceptible to cell-mediated attack.

Acute Rheumatic Fever–> streptococcus looks similar to certain protein on the heart which causes these receptors to start being degraded by immune cells as a response.

Question 10

What are the 2 types of Type 3 Hypersensitivity reactions?

Answer 10

Immune Complex Formation: Generalized & Localized

Generalized (Serum Sickness)

Localized (Arthus Reactions)

Question 11

What is the general process for Type 3 Hypersensitivity reactions?

Answer 11

It is dependent on the complement system:

Ab binds to Ab-antigen creating immuno-complex; this immunocomplex cannot be broken because macrophage activity is absent.

The Results:
The immune complex that is left behind will be activated by complement proteins which will settle in the walls of blood vessels.
- Formation of the Ag-Ab Complex
- Complement Activation
- Local necrotic Cells attack into the blood vessels

Question 12

What is the localized arthrus reaction for Type 3 Hypersensitivity reactions?

Answer 12

Type 3 hypersensitivity reaction

-characterized by localized inflammation; fever, fatigability, general lymphadenopathy, raised under the skin

Question 13

What are some other examples of Type 3 Hypersensitivity reactions?

Answer 13

Systemic Lupus Erythrematosus
Serum Sickness (General)
Arthus Reaction (Local)
PolyARTERITIS Nodosa
Post-Streptococcal Glomerulonephritis
Farmer's Lung

Question 14

What are Type IV Hypersensitivity Reactions?

Answer 14

Delayed Type Hypersensitivity Reactions:

• TH1 Cells are primarily activated
• Tuberculoid Test (Tuberculosis)
• Granuloma formation (inside epithelial cells + outside= macrophages)

Delayed Type Hypersensitivity Reactions:
Macrophage engulfment–> presentation to Th cell via IL-12–> Proliferation of many Th1 Cells (secretion of IL-2) –>clonal expansion–> Mature Th1 Cell secretion of TNF-GAMMA + IFN-GAMMA (Type 2 Interferon)

Mass migration of phagocytes to the site of infection*** to create granules around the epithelia

TNF–> increase the adhesion molecules for receptors
IFN-gamma–> recruitment of macrophages

Question 15

What are examples of Type 4 Delayed Onset Hypersensitivity Reactions?

Answer 15

• Urschiol Oil for Poison Ivy (Dermatitis)
• TB Reaction
• Multiple Sclerosis
• Diabetes Mellitus I (TH1 cell mediated, Glutamic Acid Decarboxylase Enzyme Destruction on Insulin Receptors)