C2 soluble mediators Flashcards
2 soluble blood components
complement
antimicrobial proteins
types of antimicrobial proteins and their role (are the inactive or active)
lactoferrin- binds iron
bactericidal/permeability- increasing protein
a and b defensins- cationic peptides, disrupt membranes
often present in inactive form and activated when an immune responses is taking place
what are the three pathways that activate complement and what is needed
classical
alternative
lectin
lots of proteases (an enzyme that catalyses proteolysis, breaks down proteins into smaller polypeptides/single aa, act in a controlled manner)
what is the exception to the a-small product rule
C2 where C2a is big
what do anaphylatoxins initiate with receptor example
may initiate localised inflammatory responses by binding to specific receptors such as
complement component 3a receptor 1 and complement component 5a receptor 1
what do the b in complement pathways result in and bind to
Big product
bind to targets near activation sites
opsonins ie C3b, C3dg, and iC3b interact with cell surface receptors such as complement component receptor 1
complement component receptor 2
integrins alpha-M/beta-2 integrin
alpha-X/beta-2 integrin
function of active form C1q
binds directly to pathogen surfaces or indirectly to antibody bound to pathogens thus allowing autoactivation of C1r
function of active form C1r
cleaves C1s to activate protease
function of active form C1s
cleaves C4 and C2
function of active form C4b
covalently binds to pathogen and opsonises it
binds C2 for cleavage by C1s
function of active form C4a
peptide mediator of inflammation (weak acctivity)
function of active form C2a
active enzyme of classical pathway C3/C5 convertase
cleaves C3 and C5
function of active form C2b
precursor of vasoactive C2 kinin
function of active form C3b
binds to pathogen surface and acts as opsonin
initiates amplification via the alternative pathway
binds C5 for cleavage by C2a
function of active form C3a
peptide mediator of inflammation (intermediate activity)
what is the classical pathway initiated by
by C1 components
what is the alternative pathway initiated by
by C3
what is the lectin pathway initiated by
by mannan binding protein (mannan binding ligand MBL)
end point of the lectin pathway
C3a and C5a recruit phagocytic cells to the site of infection and promote inflammation
end point of classical pathway
phagocytes with receptors for C3b engulf and destroy pathogen
end point of alternative pathway
completion of the complement cascade leads to formation of a membrane attack complex (MAC) which disrupts cell membrane and causes lysis
defensins, cathelicidins, and histatins and activated by what to release what
activated by proteolysis to release an amphipathic antimicrobial peptide
(amphipathic- peptide with both hydrophilic and hydrophobic parts
how do lysozymes act on bacteria
bacteria have an outer membrane that has carbohydrate chains, interlocked by short peptide strands
lysozymes break down carb chain and damages structural integrity of the bactrial outer membrane
bacteria burst under their own internal pressure
what are lysozymes inactive and active against
inactive against most gram -ve bacteria
cannot penetrate the outer membrane to reach peptidoglycan
very active against gram +ve bacteria
how do defensins work
disrupt membrane of pathogen forming a pore
electrostatic attraction and the transmembrane electric field bring the defensin into the lipid bilayer
where are cathelicidins stored and how are they released
stored in neutrophil granules as inactive precursors (prepropeptides
released when cleaved by neutrophil elastase
what is the one cathelicidin gene (CAMP) identified in humans, codes for what peptide
LL-37
what is LL-37 expressed in
lots of cells
circulating neutrophils, myeloid bone marrow cells
epithelial cells of skin and GI tract, epididymis and lungs
