Lecture 13 - Immunopathology Flashcards
Immunopathology =
damage caused to tissues as the result of an immune response
2 types of immunopathology
Hypersensitivity, autoimmune
Hypersensitivity disease =
disease as a result of excessive immune response to foreign antigens
Autoimmune diseases =
disease as a result of the immune system attacking self antigens
How many types of hypersensitivity diseases are there?
4
What is type 1 hypersensitivity?
Immediate hypersensitivity
What happens in type 1 hypersensitivity?
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)
What does histamine cause?
increased vascular permeability, extravasation of fluid, oedema, dilation of cutaneous blood vessels (causes redness)
Name an example of a type 1 hypersensitivity disease
Bee venom allergy:
- IgE against phospholipase A
- Local: swelling and redness
- Systemic: anaphylaxis (fall in bp, urticaria and wheezing)
What is type 2 hypersensitivity disease?
Cytotoxic (antibody mediated)
What happens in a type 2 hypersensitivity disease?
IgG or IgM produced against cell surface antigens:
- Complement and phagocytic mechanisms
- Antibody-dependent cellular cytotoxicity
- IgG against cell surface receptors → disruption of normal receptor function
Name an example of type 2 hypersensitivity
ABO blood group incompatibility (IgM)
What is type 3 hypersensitivity?
Immune complex reactions
What happens in a type 3 hypersensitivity disease?
Involves soluble antigens that bind antibodies to form an immune complex -> deposition of antigen -> fixation of complement -> leukocyte activation
Name a type 3 hypersensitivity disease
Arthus reaction
What is type 4 hypersensitivity?
Delayed type hypersensitivity
What happens in type 4 hypersensitivity?
CD4 and CD8 T cells react to an antigen -> tissue damage due to macrophages, eosinophils or direct cytotoxins
Name an example of a type 4 hypersensitivity reaction
The Mantoux test
Why do autoimmune diseases develop?
Due to random rearrangements of antigen receptor gene segments in T and B cells, which can then become autoreactive
What are the 2 types of autoimmune thyroid disease?
Hypothyroidism, hyperthyroidism
What happens in hypothyroidism?
Auto-antibodies against thyroid peroxidase cause the death of thyroid cells. Cytotoxic T Cells also contribute to the destruction of the thyroid gland.
What happens in hyperthyroidism?
Auto-antibodies against the receptor for thyroid stimulating hormone -> Antibodies bind to the TSH receptor → over-production of thyroid hormones
Name more autoimmune diseases
MS, T1 Diabetes, Lupus, Rheumatoid arthritis, Celiac disease
Why is celiac disease not a classic autoimmune disease?
The gluten have to be present to provoke the immune response
What happens in MS?
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
What happens in T1 Diabetes?
Cytotoxic T cells destroy the beta cells of the pancreas -> no insulin production
What happens in systemic lupus erythematosus?
Development of antibodies to many self antigens incl DNA -> chronic inflammatory disease.
Immune complex deposition in kidneys
What happens in rheumatoid arthritis?
Infiltration of the synovium by B cells -> production of auto-antibodies, CD4 T cells, macrophages, neutrophils -> cartilage damage -> bone erosion
What happens in celiac disease?
Immune response against gluten. T cells, B cells and macrophages infiltrate -> loss of villi -> normal absorption and digestion impaired
