Hypersensitivity and Autoimmunity Flashcards
Define hypersensitivity.
A group of disorders in which the normally beneficial components of the immune response act in an exaggerated or inappropriate fashion to environmental antigens which don’t usually cause the tissue damage.
What is responsible for the tissue damage?
Exaggerated immune response.
What are hypersensitivity types 1, 2 and 3 mediated via?
Antibodies.
What cause type 4 hypersensitivity?
Inappropriate actions of T helper 1 cells
What is the other name for type 1 hypersensitivity?
Allergy
What is type 1 hypersensitivity caused by?
Inappropriate synthesis of IgE.
In what 4 ways can a type 1 hypersensitivity reaction be started?
Ingestion
Inhalation
Injection
Skin contact
What are allergens?
Antigens which cause IgE production.
What are the 5 factors of immunity? RIREC
Recognition Interaction Response Elimination Control and Regulation
What allows IgE to bind to Fc receptors?
It has an extra peptide sequences to other immunoglobulins.
Where are Fc receptors found?
On the surface of mast cells.
What do T helper cells do?
Aid B-cells in producing IgE
What are the 3 types of Th1 cells?
IL-2
Gamma - IFN
TNF
What are the 4 types of Th2 cells?
IL- 4
IL - 6
IL - 10
IL - 13
Define atopy.
A genetic tendency to produce IgE to normally innocuous, common environmental allergens.
Define allergy.
A clinical expression of the atopic tendency.
What % of the population suffers from allergy?
15-20%.
What are 3 specific triggers of IgE?
Insect venom Pollen Mould spores Animal dander Food allergens
What are 3 nonspecific triggers of IgE?
Exercise Tobacco Pollution SO2 Water Food items
What are the 5 symptoms of allergy and atopy?
Anaphylaxis Asthma Rhinitis and Conjunctivitis Urticaria Gastrointestinal
What is the main preformed mast cell mediator?
Histamine
What are the 2 newly synthesised mast cell mediators?
Prostaglandins
Leukotrienes
What mast cell causes early phase response?
Preformed
What mast cell causes late phase response?
Newly synthesised
What 2 things mediate type 2 hypersensitivity?
IgG
IgM
What are the target antigens in type 2 hypersensitivity?
Self
Exogenous
Where are the target antigens found in type 2 hypersensitivity?
on the surface of or fixed within cells.
In what 4 ways does damage to tissue arise in type 2 hypersensitivity?
Complement activation
Fc receptor-mediated damage
Antibody dependent cellular cytotoxicity
Effects on target function i.e inhibition
What are the 2 types of immune complex formation?
Normal
Pathological
What is formed in an immune complex formation?
Lattice due to antigens having 2 binding sites.
What are the 3 protective mechanisms of a normal immune complex?
Opsonization
Transportation
Destruction
What causes the clinical conditions to arise in in type 3 hypersensitivity?
Abnormal deposition of formed antigen/antibody complexes in tissues.
What is the process of serum sickness?
Immune complexes form in circulation causing systemic deposition in tissues.
What is the process of arthus reaction?
Immune complexes form locally in tissues.
What happens to immune complexes formed normally after gaining access to the blood stream?
Kept soluble in the blood and transported to the liver and spleen for phagocytosis.
What is the job of Th1 cells in type 4 hypersensitivity?
Mediator
In general, why do type 4 hypersensitivity reactions take place?
As the body’s immune system finds it hard to destroy the environmental agents causing the problem.
What is a hapten?
The low molecular weight agent which has so bind to a carrier to produce an antigenic stimulus of sufficient size for a response.
How long a delay is there is type 4 hypersensitivity?
48-72 hours
The hapten is ___genous and the carrier is ___genous.
Exo, endo.
Define autoimmune disease.
A large group of clinical disorders which are characterised by tissue or organ damage mediated through immunological mechanisms which are directed against autoantigens.
What is another name for autoantigens?
Self antigens
What are the two types of roles an autoantigen can do?
Non-organ specific
Organ specific
Define tolerance.
The process whereby the immune system avoids producing damaging reactions against self antigens.
How does central tolerance arise?
Deletion of autoreactive T and B cells.
How does peripheral tolerance arise?
Inhibiting the activity of autoreactive cells which escape the central tolerance process.
What is the breakdown of a tolerance process a requirement for?
Autoimmune disease
What are the 5 aetiologies of autoimmune disease?
Genetic factors Immune regulatory factors Hormonal factors Environmental factors Other factors
What are the 5 effector mechanisms of autoimmune disease? (Pathogenesis)
Cell mediated Antibody mediated Antibody and complement Immune complex mediated Recruitment of innate components
What type of disease is organ specific?
Diabetes
What type of disease is non-organ specific?
Connective tissue
