Allergy Flashcards
What is Hypersensitivity
Damage to the host arises from the immune response.
What is Allergy
Hypersensitivity resulting from innocuous stimuli
What are causes for hypersensitivity (2)
Allergy
Autoimmunity
What are the 6 types of hypersensitivity
Type I Type II Type III Type IV Type V Innate
What is the immediate mechanism of Type 1 Hypersensitivity (4)
IgE Produced
Fce RI (epsilon) binds IgE
IgE binds to allergen
Degranulation
What are the inflammatory mediators released during degranulation of Type 1 hypersensitivity (5)
histamine serotonin TNFa (alpha) Prostoglandins Leukotruienes
What is the long term action of type 1 hypersensitivity (2)
Th2 cells activate mast cells and release IL4 and IL13 which activate B cells
B cells produce IgE, which joins mast cells in the epithelium and endothelium
What are common examples of type 1 hypersensitivity (4)
URT: Rhinitis, Hay Fever
LRT: Asthma
Skin: Allergic eczema
Systemic: Peanuts
Why is peanuts allergy systemic
IgE Produced everywhere in the body
What is the hygienic hypothesis (2)
A clean environment reduces the exposure to environmental bacteria, offsetting the balance of Th1 and Th2 cells
Causes a larger Th2 cell response, and allergies
What are treatment options for Type 1 Hypersensitivity
Allergen Avoidance
Pharmacotherapy
Immunotherapy
What is a summery for type 2 hypersensitivity
Cytotoxic antibody against cell surface antigens
What is a unique to type 2 hypersensitivity
Complement activated
What are examples of type 2 hypersensitivity
transplantation
Haemolytic disease of the newborn (HDN)
Streptococcal endocarditis
Autoimmune diseases, Goodpasture’s syndrome
How does haemolytic disease of the newborn happen
RhD+ baby causes bleed in RhD- mother
Mother produces IgG Anti-D against Rh+ 2nd baby
Antibody crosses from mother to baby, introducing the IgG into the baby
What is an example of type V hypersensitivity
Graves Disease
How does Type III hypersensitivity work
The antibody binds to antigen in the blood
Complex forms, causing a blockage in the vessel
Neutrophil comes to break up immune complex, causing inflammation and clotting
What is an example of type III hypersensitivity
Farmers Lung
How does Type IV hypersensitivity work (3)
Peptide-MHC binds with TCR on Th1 cell
Th1 cell releases cytokines, activating macrophage
Macrophage releases TNF and Interferon y (gamma) which further activate macrophages
How long does it take for a type IV hypersensitivity to form
Hours
What causes the swelling in a Mantoux test
macrophages
What has over activation of macrophages been associated with (3)
Atherosclerosis
Alzheimer’s
type II Diabetes
What are the 3 types of graft rejection and their time frames
Hyperacute - Minutes
Acute - Several days to a few weeks
Chronic - months to years
What is the cause of hyper acute graft rejection
Pre-existing antibodies to blood groups or to MHC by pre-sensitisation
