Lecture 20 Flashcards
what are hypersensitivity diseases
diseases caused by immune system
how do hypersensitivity diseases work
when responses are not adequately controlled the immune system becomes the cause of the disease
how many types of hypersensitivity diseases are there
4
what is type 1
IgE mediated for allergic responses
what are IgE responses needed for
responding to large complex molecules
how does mast cell degranulation work
IgE binds to Fc receptor on the outside of the mast cell which activates the cell for degranulation. Granules are released off of the outside of the cell which causes a cross link between IgE and antigens on mast cells. this causes the release of mediators
what are the mediators released during mast cell degranulation
chemoattractants, activators and spasmogens
what are chemoattractants
tell other immune cells to get to sites
what are activators
increase blood glow at the site
what are spasmogens
compounds which have roles in muscle contractions and mucus secretions
what are allergies
misdirected IgE responses
what are 4 types of allergies
hay fever caused by dust pollen
insect stings caused by proteins in venom
food allergies caused by wheat protein, milk protein, peanuts
small molecules caused by penicillin, codeine
what is the sensitisation phase
mast cells are coated with allergen specific IgE and remain armed for a period of time
what does the sensitisation phase do
gets memory to allergen after first exposure
what does IgE do during the sensitisation phase
sit on the receptor of the mast cell without the specific allergen bound
what is the effector phase
allergen enters a second time while mast cells already armed triggering a hypersensitivity reaction
what are the steps of the sensitisation and effector phase
1) first exposure to allergen
2) activation of Th2 cells and stimulation of IgE class switching to B cells
3) production of IgE specific to allergen
4) binding of IgE to Fc receptor on mast cells and gets hypersensitivity reaction from first exposure resulting in pre loaded mast cells towards specific allergen
5) repeat exposure to allergen
6) immediate activation of mast cells and release of mediators
7) immediately gets lots of symptoms occurring instantly
what are the common sites of allergies
gut, skin, respiratory tract and multiple organs (anaphylaxis)
what are treatments of allergies
avoidance, antihistamines, corticosteroids, epinephrine, desensitisation
how are allergies tested for
blood test through the presence of IgE antibodies in blood and skin prick test which needles coated in diluted antigen
what is the hygiene hypothesis
change in environment results in a change in lifestyle
what is type 2
antibodies binding to antigens on the surface of cells and cause lysis
what antibodies are present in type 2
IgM and IgG
what do antibodies attack in type 2
mobile cells in bloodstream
what is phagocytosis (hemolytic anemia)
IgG coated RBC are cleared from circulation via uptake of Fc receptor bearing macrophages and IgM coated RBC are fixed by complement and directly lysed
what is goodpastures syndrome
antibodies against type 4 collagen in glomerular affects the kidney and aleveoli in the lungs
what happens in goodpastures syndrome
antibodies trigger complement activation that damages epithelial cells
what is type 3 mediated by
IgG
what does type 3 do
antibodies bind antigens and form complexes which gets lodged into places it shouldnt be in and induces an inappropriate inflammatory response
what is an example of type 3
rheumatoid arthritis and serum sickness
what is type 4 mediated by
T cells
how does type 4 mediated work
delayed hypersensitivity which results in trafficking
what is an example of type 4
contact sensitivity caused by direct contact with certain antigens
