Thrush- Complement Cascade Flashcards
what are the functions of the complement cascade?
causes cell lysis, results in opsonization (tagged substance removed by phagocytic cells) of Ag and mediates inflammation
if a cell is going to be lysed, what are the membrane attack complexes (MAC) that need to be used?
MAC C5b-C9
of the 30 different proteins required for the complement cascade activation, which area of the body is most important site of synthesis for these proteins?
the liver
once the proteins are activated they are generally split into components. which of the fragments is more likely to stimulate inflammation and which is likely to remain bound to the target cell?
smaller fragment-> inflammation
larger fragment-> bind to target cell
what antibodies can activate the classical pathway? and what regions have to be close to C1 to help activation?
IgG and IgM.
multiple Fc regions (at least 2) need to be in close proximity C1 for binding and then activation
if a patient has a mutation for a faulty C3, how will the complement cascade be affected?
the complement cascade wont work because C3 is the branch point
what is the importance of C3a?
is stimulates inflammation
how is the alternative pathway activated?
by surface components (bacterial LPS, cell wall components) binding to C3b
the MBP (lectin) pathway is activated by what?
collectins like Mannan-binding protein that activate the cascade by binding a microbe to its lectin binding domain and having cell interaction at its collagen domain
is it more likely that the classical pathway be activated via IgM binding or IgG binding?
IgM because it contains 5 Fc regions in one molecule, where as 2 IgG molecules would need to be next to each other for possible activation
what binds to Ch2 in the classical pathway? and upon binding what does it allow to take place?
C1q binds to Ch2.
upon binding C1r activates C1s
what does C1s activate? and how does it lead to the production of an enzyme?
activates C4 and C2.
C4b then binds to C2a (C4a and C2b float and diffuse away respectively). C3 convertase is the product of C4b2a
C3 is cleaved by C3 convertase. but which subunit (C3b or C3a) binds with C4b2a to form C5 convertase? what happens with the other subunit?
C3b binds to C4b2a to form C5 convertase.
C3a diffuses away to become an inflammatory meidator
what creates the Membrane attack complex (MAC)? and what does it cause?
when C5b binds C6, C7, C8, C9.
causes lysis
in the alternative pathway what are some initiators?
LPS, teichoic acid (gram positive bacteria), zymosan (fungal/yeast wall), viruses, parasites, human IgG, IgA and IgE complexes