Hypersensitivity 2 Flashcards
what is the type 2 hypersensitivity reaction?
small molecules that modify cell-surface components perceives as foreign by the immune system
which antibody does type 2 depend on?
what is type 2 also known as?
IgG
antibody-dependent cytotoxicity
what are the 3 main aspects of type 2?
- phagocytes
- NK cells
- complement mediated cell lysis
describe the process involving phagocytes in type 2
- epitopes result in normal cell being mistakenly recognised as non-self
- IgG bind to epitope
- Fc binds to Fc receptor on phagocyte
- Lysosome migrates to phagocyte membrane and content is released
- Self cell lysis
describe the process involving NK cells in type 2
- epitopes result in normal cell being mistakenly recognised as non-self
- IgG bind to epitope
- Fc binds to Fc receptor on NK cell
- NK cell releases perforin and granzyme
- lysis of self cell
describe the process involving complement activation in type 2
which type of pathway is involved?
- epitopes result in normal cell being mistakenly recognised as non-self
- IgG bind to epitope
- C1 binds to bound IgG
- MAC form on self cell surface
- cell lysis
classical pathway
what can also lead to phagocytosis?
what is ADCC?
opsonisation via complement components
antibody dependent cell mediated cytotoxicity
give some examples of type 2 hypersensitivity
blood transfusion reactions
haemolytic disease of the newborn (Rh disease)
drug reactions
Myasthenia gravis (ACh receptor)
explain the differences between ABO blood group antigens
sugars on the surface of RBCs
H antigen
= N-acetyl glucosamine + galactose + fructose
A antigen
= NAG +Gal + Fuc + N-acetylgalactoseamine
B antigen
= NAG + Gal + Gal + Fuc
why do we have different food groups?
having glycosylation of cells in the way microbes get into cells by binding to sugars on the surface
may be less vulnerable to infections by changing sugars on surface
who are the potential donors of each blood group?
why is this?
O = O only
(anti A and B antibodies)
A = O or A
(anti B antibodies)
B = O or B
(anti A antibodies)
AB = O, A, B or AB
(no antibodies)
describe hemoltyic disease of the newborn
RhD- mother can carry an RhD+ foetus
During delivery placenta can rupture
-> some foetal blood enters mother’s system
-> unrecognised antigen
= immune réponse
foetal RBCs trigger B cells to produce IgG targeting antigen
if there’re subsequent RhD+ children
-> mother will have antibodies that can cross placenta
-> recognise RhD+ RBCs
= lyse cells via type 2 hypersensitivity
describe drug induced reactions
e.g. Penicillin
Beta lactam ring of penicillin modified proteins on RBCs
- > creates foreign epitope
- > phagocytosis
describe what happens after complement-coated penicillin-modified RBCs are phagocytosed
- macrophage present peptides from penicillin-protein conjugate
- activate CD4 T cells to become Th2 cells
- B cells activated bu antigen + Th2 cells
- plasma cells secrete penicillin-specific IgG which binds to modified RBCs
- activate complement components C1-C9
-> MAC formation
= lysis
OR
- activates complement components C1-C3
- > phagocytosis
describe what happens in Myasthenia Gravis
- motor neurone releases ACh
- antibodies recognise ACh receptor
- classical complement pathway and immune cell activation
(4. no muscle contraction) - inflammation
- break down muscle membrane
