Immunopathology Flashcards
Define immunopathology
Damage caused to tissues as the result of an immune response
What are the 2 types of disease caused by the immune system?
- Hypersensitivity diseases
- Autoimmune diseases
What are hypersensitivity diseases?
Diseases that occur as a result of excessive or increased immune responses to ‘foreign’ antigens
What are autoimmune diseases?
Diseases which occur as a result of the immune system responding to ‘self’ antigens
What is type 1 hypersensitivity?
Immediate hypersensitivity
Outline the process of type 1 hypersensitivity
- IgE produced against a harmless antigen
- IgE binds to Fc receptors on mast cell surface
- Soluble antigen binding to Fc receptor bound
- Mast cells release chemical mediators which leads to inflammation
Give examples of type 1 hypersensitivity
- allergic asthma
- hay fever
- atopic eczema
How are mast cells activated?
By antigen cross-linking
What receptor for IgE do mast cells carry?
FcƐR1
What is characterstic of a local hypersensitivity reaction in the skin?
Wheal-and-Flare reaction
Why can circulatory collapse occur as a result of anaphylatic shock?
Permeability of blood vessels is increased which prevents organs from getting enough blood
What are Type II hypersensitivity reactions?
Cytotoxic/antibody-mediated
Which antigen(s) are involved in type II hypersensitivity reactions?
IgG and IgM
What occurs in type II hypersensitivity reactions?
- Complement and phagocytic mechanisms
- Antibody-dependent cellular cytotoxicity
- IgG against cell surface receptors causing disruption of normal function
Which type of immune reaction occurs in incompatible blood transfusions?
type II hypersensitivity reactions
What kind of antibodies are generated in the hypersensitivity reaction against bee venom?
IgE
What is the effect of histamine on blood vessels?
It increases vascular permeability
What are the local effects of bee venom?
Immediate swelling and redness at a sting site
What is the systemic response to bee venom?
- Hives
- Fall in blood pressure
- Wheezing
Why may a systemic response occur to bee venom?
Mast cells degranulate all over the body
Which classes of immunoglobulins fix complement?
IgM and IgG
Outline the initiation of the complement cascade
- Pentameric IgM molecules bind to antigens on bacterial cell surface
- IgG molecules bind to bacterial cell surface
- Cq1 then binds to either the IgM or IgG molecules
What are the symptoms of haemolytic disease of the newborn?
Why?
Enlarged liver and spleen due to macrophages phagocytosing IgG coated fetal red blood cells
What are type III hypersensitivity reactions?
What do type III hypersensitivity reactions involve?
- Soluble antigens which bind antibodies to form an immune complex
- Deposition of antigen:antibody complexes in blood vessel walls
What are the effects of antigen:antibody complex deposition in type III hypersensitivity reactions?
- Fix complement
- Ligate Fc receptors
- Leukocyte activation
- Tissue damage
What is seen in a subcutaneous Type III hypersensitivity reaction?
Arthus reaction
What is a type IV hypersensitivity reaction?
Delayed type hypersensitvity
What immune cells does a type IV hypersensitivity reaction involve?
CD4+ and CD8+ T cells
Does a type IV hypersensitivity reaction involve antibodies?
No
How is tissue damage caused in type IV hypersensitivity reaction?
- Th1 cell activation of macrophages
- Th2 cell activation of eosinophils
- Direct cytotoxicity via cytotoxic T cells
What is the mantoux test?
A test done to find whether someone has previously been exposed to TB
Outline what occurs in a mantoux test
- Tuberculin is injected intradermally
- A local inflammatory T cell response occurs
What is seen in a positive result for the mantoux test?
A visible lesion
Why does the lesion develop 24-72 hours after injection in the mantoux test?
Antigen-specific Th1 are rare so it takes time for the cells to migrate and recruit macrophages
What type hypersensitvity response is exploited in the mantoux test?
Type IV
What is an autouimmune disease?
Conditions where the immune system reacts to antigen contained within the patient’s body, auto-antigens, by producing auto-antibodies
Give 2 examples of antibody-mediated autoimmune disease
- Systemic lupus erythematosus
- Autoimmune thryoiditis
What causes the symptoms of Systemic Lupus Erythematosus?
Patients develop antibodies to many self antigens including DNA
What type of hypersensitivity reaction causes Lupus?
Type III
How does damage to the kidneys occur in lupus?
- Autoantibodies bind to their antigens and immune complexes are formed
- Immune complexes deposite in the kidneys
- This leads to kidney damage
Give 3 examples of cell-mediated autoimmune disease
What causes Hashimoto’s thyroiditis?
Auto-antibodies against thyroid peroxidase causes death of thyroi cells
What are the symptoms of hypothyroidism?
- Tirerdness
- Depression
- Weight gain
What is the name of autoimmune hypothyroidism?
Hashimoto’s thyroiditis
How is hashimoto’s thyroiditis treated?
Synthetic thyroid hormone
What is the name of autoimmune hyperthyroidism?
Grave’s disease
What causes Grave’s disease?
- Auto-antibodies against the receptor for thyroid stimulating hormone
- Antibodies bind to the TSH receptor
- Causes over-production of thyroid hormones
What causes multiple sclerosis?
- T cells migrate to the central nervous system where they destroy myelin sheaths
What are the symptoms of Grave’s disease?
- Goitre (swollen thyroid gland)
- Exopthalmia (bulging eyes)
How is Grave’s disease treated?
With antithyroid drugs or thyroidectomy
What are cell mediated autoimmune diseases?
What are the symptoms of mutiple sclerosis?
- Loss of nerve function
- Death of nerves
- Varying degress of disability
What causes rheumatoid arthritis?
Infiltration of the synovium by B cells and CD4 T cells, macrophages, and neutrophils
What causes Type 1 diabetes?
Cytotoxic T cells destroy the insulin producing β cells of the pancreas
How is celiac disease different to other autoimmune diseases?
- It has features of both a hypersensitivity response and autoimmunity
- Gluten must be present to provoke the immune response
