Type 1 Hypersensitivity Flashcards
What is type 1 hypersensitivity associated with?
Anaphylactic reactions (IgE - mediated).
What is an allergen?
Substance which when eaten // inhaled is recognised by the immune system as being foreign and causes an allergic reaction.
Name some examples of allergens.
House dust mites
Fungi
Domestic pets
What does antigenic mean?
Any substance which is foreign to the body and evokes an immune response by forming a complex with a LARGER molecule and binds with a product of the immune response.
What is the product of an immune response?
Antibody or T - cell.
What does immunological hypersensitivity mean?
Undesirable reactions produced by the normal immune system.
How does the immune response begin?
Begins with sensitisation.
What does antigen presenting cells do?
They internalise the allergen : process and express the allergens on their cell surface.
What do the allergens do?
They present these to the t - cells.
B - lymphocytes are transformed into antibody secretory cells - plasma cells.
What does the plasma cells produce?
Produces IgE - antibodies which BIND to the specific allergen.
Where does the IgE antibodies bind to?
These bind to high affinity receptors on mast cells : leaving the allergen receptor site for future interaction.
What is the happen model?
These are small molecule irritants which BIND to proteins and elicit an immune response.
What is sensitisation?
Production of allergen specific IgE - antibodies and this completes the immune response.
Where are mast cells derived from?
Comes from the bone marrow.
Where are mast cells located?
These are located at the boundaries between tissues and external environment (mucosal surfaces of the gut).
Why are mast cells important?
They are key as they can be activated to release a wide variety of mediators.
What are mast cells associated with in terms of disease?
Asthma // Autoimmune disease // Rhinitis // Parasite. Infection
What is the purpose of mast cell mediators?
Initiate both early and late inflammatory events.
What is the purpose of histamines?
Increases vascular permeability and smooth muscle contraction.
What is the purpose of Interleukin - 4 and Interleukin - 13?
Promotes Th2 and IgE production.
What is the purpose of TNF - alpha?
Promotes tissue inflammation.
What is the purpose of Leukotrienes and Prostaglandins?
Increases vascular permeability and causes muscle contraction.
What is the purpose of IgE independent mechanisms?
These initiate signals which INDUCE cellular degranulation with release and secretion of vasoactive mediators // enzymes // cytokines.
What are basophils?
This is a type of white blood cell which is found in MANY tissues throughout your bodies.
What does basophils contain?
These contain histamines which promote the flow of blood to the tissues.
What is the indication if basophil levels are low?
This is due to a SEVERE allergic reaction.
How can basophils be activated?
They can be activated via pathogen - associated molecular patterns.
What are the 2 cell surface receptors?
FceI
FceII
Which is the cell receptor which has low affinity binding?
FceRII
Which is the cell receptor which has high affinity binding?
FceRI
What is a trimer?
3 non - covalent bound macromolecules.
What is compound degranulation?
Cellular process which releases cytotoxic molecules from granules found inside SOME cells.
What are inflammatory mediators?
Messengers which act on blood vessels and promote an inflammatory response.
What is the most common inflammatory mediator?
Histamine = Triggers vasodilation and increases vascular permeability.
What is IgE cross linking?
This is when IgE molecules cross link and thus intracellular signalling occurs.
What are peptidergic neurotransmitters?
These stem from the endocrine hypothalamus and exert neurohormonal effects.
What is neurogenic inflammation?
These are mediators which are released directly from the nerves to initiate an inflammatory reaction.
What is anaphylaxis?
This is an extreme and severe allergic reaction.
What are the 2 types of anaphylaxis?
Uniphasic = Symptoms get worse QUICKLY. Biphasic = Mild // Severe symptoms but there are also periods of time where there is NO symptoms.
