Hypersensitivity

Question 1

What is hypersensitivity?

Answer 1

Hypersensitivity is the altered reactivity which the body reacts with an exaggerated immune response to a foreign agent

Question 2

What hypersensitivity reaction type are Allergies?

Answer 2

Type 1 Hypersensitivity

Question 3

What is an allergen?

Answer 3

An antigen that causes an allergic reaction

Question 4

What is Gell & Coomb’s classification?

Answer 4

The 4 classes/types of hypersensitivity (antibody responses)

Question 5

What is Type 1 hypersensitivity?

Answer 5

IgE Mediated

• Most common/rapid
• Occurs rapidly in response to allergen, can be haptens or proteins (antigen)

Question 6

What is a Hapten?

Answer 6

A small molecule that can be recognised by a specific antibody but DOES NOT elicit an immune response unless combined with a carrier

Question 7

What are the role of mast cells and antibodies to an allergen (or hapten)?

Answer 7

• Immune cell recruitment

- Antibodies bind to allergen/Hapten releasing inflammatory molecules -> Allergy symptoms

Question 8

What does Atopy mean?

Answer 8

Localised response

Question 9

What is anaphylaxis?

Answer 9

Rapid systemic response - Potentially life threatening

Symptoms:
itchy rash, throat or tongue swelling, shortness of breath, vomiting, lightheadedness, and low blood pressure.

Question 10

How can you test for allergy?

Answer 10

• Skin prick test
• Patch test
• Blood test

Question 11

What are treatment options for allergy?

Answer 11

• Anti-histamines: compete with histamine (causes itching) for receptors
• Epinephrine (EpiPen - Anaphylactic shock; nut allergy?)
• Many more

Question 12

What is Type 2 Hypersensitivity?

Answer 12

Cytotoxic response

• Involves activation of complement system resulting in cell being lysed by CD8+ T cells (rupture of cell wall/membrane - lysis)

Question 13

What is Type 3 Hypersensitivity?

Answer 13

Immune complex response; reactions against antigens circulating in blood

Reactions result in:
- Complement activation
- Neutrophil recruitment
Inflammation-mediated damage

Question 14

What is Type 4 Hypersensitivity?

Answer 14

T-Cell mediated responses (no antibodies)

• Sometimes called delayed hypersensitivity - takes time to recruit T cells
• Involves CD4+ (inflammation induced damage via macrophages) & CD8+ (cytotoxicity) T cells

OROFACIAL GRANULOMATOSIS (OFG) is Type 4 hypersensitivity