Lecture 13 - Immunopathology

Question 1

Immunopathology =

Answer 1

damage caused to tissues as the result of an immune response

Question 2

2 types of immunopathology

Answer 2

Hypersensitivity, autoimmune

Question 3

Hypersensitivity disease =

Answer 3

disease as a result of excessive immune response to foreign antigens

Question 4

Autoimmune diseases =

Answer 4

disease as a result of the immune system attacking self antigens

Question 5

How many types of hypersensitivity diseases are there?

Answer 5

4

Question 6

What is type 1 hypersensitivity?

Answer 6

Immediate hypersensitivity

Question 7

What happens in type 1 hypersensitivity?

Answer 7

IgE is produced against a harmless antigen. Then binds to Fc receptor in mast cell surface. Mast cell will release chemical mediators (E.g. Histamine)

Question 8

What does histamine cause?

Answer 8

increased vascular permeability, extravasation of fluid, oedema, dilation of cutaneous blood vessels (causes redness)

Question 9

Name an example of a type 1 hypersensitivity disease

Answer 9

Bee venom allergy:

• IgE against phospholipase A
• Local: swelling and redness
• Systemic: anaphylaxis (fall in bp, urticaria and wheezing)

Question 10

What is type 2 hypersensitivity disease?

Answer 10

Cytotoxic (antibody mediated)

Question 11

What happens in a type 2 hypersensitivity disease?

Answer 11

IgG or IgM produced against cell surface antigens:

1. Complement and phagocytic mechanisms
2. Antibody-dependent cellular cytotoxicity
3. IgG against cell surface receptors → disruption of normal receptor function

Question 12

Name an example of type 2 hypersensitivity

Answer 12

ABO blood group incompatibility (IgM)

Question 13

What is type 3 hypersensitivity?

Answer 13

Immune complex reactions

Question 14

What happens in a type 3 hypersensitivity disease?

Answer 14

Involves soluble antigens that bind antibodies to form an immune complex -> deposition of antigen -> fixation of complement -> leukocyte activation

Question 15

Name a type 3 hypersensitivity disease

Answer 15

Arthus reaction

Question 16

What is type 4 hypersensitivity?

Answer 16

Delayed type hypersensitivity

Question 17

What happens in type 4 hypersensitivity?

Answer 17

CD4 and CD8 T cells react to an antigen -> tissue damage due to macrophages, eosinophils or direct cytotoxins

Question 18

Name an example of a type 4 hypersensitivity reaction

Answer 18

The Mantoux test

Question 19

Why do autoimmune diseases develop?

Answer 19

Due to random rearrangements of antigen receptor gene segments in T and B cells, which can then become autoreactive

Question 20

What are the 2 types of autoimmune thyroid disease?

Answer 20

Hypothyroidism, hyperthyroidism

Question 21

What happens in hypothyroidism?

Answer 21

Auto-antibodies against thyroid peroxidase cause the death of thyroid cells. Cytotoxic T Cells also contribute to the destruction of the thyroid gland.

Question 22

What happens in hyperthyroidism?

Answer 22

Auto-antibodies against the receptor for thyroid stimulating hormone -> Antibodies bind to the TSH receptor → over-production of thyroid hormones

Question 23

Name more autoimmune diseases

Answer 23

MS, T1 Diabetes, Lupus, Rheumatoid arthritis, Celiac disease

Question 24

Why is celiac disease not a classic autoimmune disease?

Answer 24

The gluten have to be present to provoke the immune response

Question 25

What happens in MS?

Answer 25

T cells migrate in to the central nervous system where they orchestrate and cause destruction of the myelin sheaths -> loss of nerve function/death of nerves

Question 26

What happens in T1 Diabetes?

Answer 26

Cytotoxic T cells destroy the beta cells of the pancreas -> no insulin production

Question 27

What happens in systemic lupus erythematosus?

Answer 27

Development of antibodies to many self antigens incl DNA -> chronic inflammatory disease. Immune complex deposition in kidneys

Question 28

What happens in rheumatoid arthritis?

Answer 28

Infiltration of the synovium by B cells -> production of auto-antibodies, CD4 T cells, macrophages, neutrophils -> cartilage damage -> bone erosion

Question 29

What happens in celiac disease?

Answer 29

Immune response against gluten. T cells, B cells and macrophages infiltrate -> loss of villi -> normal absorption and digestion impaired