Hypersensitivity Type 4

Question 1

What is a type 4 hypersensitivity response?

Answer 1

Delayed type hypersensitivity

Question 2

Give 3 examples of autoimmune type 4 hypersensitivity diseases?

Answer 2

Type 1 diabetes
Psoriasis (Red flaky skin)
Rheumatoid arthritis

Question 3

Give 5 examples of non autoimmune type 4 hypersensitivity diseases?

Answer 3

Contact dermatitis (nickle allergy)
TB
Leprosy
Sarcoidosis
Cellular rejection of solid organ transplant

Question 4

What is the pathophysiology of type 4 hypersensitivity reactions?

Answer 4

1) T cell mediated hypersensitivity
2) Initial sensitisation to antigen => generation of primed effector T helper 1 cells and memory T cells
3) Subsequent exposure => activation of primed T cells.
==> Recruitment of macrophages, lymphocytes and neutrophils and the release of proteolytic enzymes and persistent inflammation.

Question 5

How are CD8+ effector T cells involved in some type 4 diseases?

Answer 5

They kill antigen positive host cells

Question 6

What do T helper 1 cells release?

Answer 6

Chemokines
Cytokines- IFN gamma, IL3
Cytotoxins- TNF alpha, Leukotrienes

Question 7

What does IL3 do?

Answer 7

Stimulates monocyte production by T cells

Question 8

What do leukotrienes do?

Answer 8

Local tissue damage and increase the adhesion molecules