Hypersensitivity

Question 1

Hypersensitivity

Answer 1

• hypersensitivity occurs when the immune system fights a harmless threat and damages tissue.

Question 2

Type 1 Hypersensitivity
IgE mediated
Immediate

Answer 2

• immediate or acute hypersensitivity
• allergies = pollen, cat fur, insect stings, peanuts and eggs.

An allergic reaction occurs in two stages :
- sensitization which is the first exposure
- subsequent exposure which means it gets more serious

One of the major mediators released in an allergic reaction is histamine. Histamine causes smooth muscle contraction which can cause difficulty breathing. It can also cause blood vessel dilation.

Late phase reaction involves the attraction of basophils and eosinophils through the production of leukotrienes. Leukotrienes facilitate communication

Treatments for hypersensitivity involve :
- antihistamines which reduce vascular permeability and reduce bronchoconstriction
- Corticosteroids which reduces inflammatory response
- EPINEPHERINE = can help constrict blood vessels and prevent anaphylactic shock

EXAMPLES OF TYPE 1 HYPERSENSITIVITY REACTIONS :
- allergic rhinitis
- asthma
- systemic anaphylaxis

Question 3

Type 2 hypersensitivity
Cytotoxic hypersensitivity
Specific organ or tissue

Answer 3

• IgM or IgG
• can bind to cell membranes or extracellular matrix and cell surface receptors

EXAMPLES OF TYPE 2 HYPERSENSITIVITY REACTIONS :
- drug allergies such as penicillin allergy
- chronic urticaria

Question 4

Type 3 Hypersensitivity

Answer 4

• mediated by immune complexes
• IgG or IgM
• type 3 hypersensitivity involves soluble antigens
• requires previous sensitization

SERUM SICKNESS
- foreign serum leads to antibody response
- the body would make antibodies against this foreign serum.

EXAMPLES OF TYPE 3 HYPERSENSITIVITY REACTIONS :
- serum sickness
- arthus reaction

Question 5

Type 4 Hypersensitivity

Answer 5

• cell mediated or delayed hypersensitivity
• not an antibody response
• T cell response

T-helper cell 1 release cytokines and chemokines.

T-helper cell 2 = eosinophil activation which causes chronic inflammation and tissue damage

EXAMPLES OF TYPE 4 HYPERSENSITIVITY
- contact dermatitis
- tuberculin reaction
- chronic asthma
- chronic allergic rhinitis