Immunology week 4 Flashcards
What is the complement system?
Inert proteins(like 30 of them) that are activated by pathogens
○ They have to be cleaved to become activated
○ If they aren’t activated they aren’t useful!
○ Basically a domino effect
What is the complement system?
Inert proteins(like 30 of them) that are activated by pathogens
what is required to become activated?
Is activation necessary?
What is the complement system?
● Inert proteins(like 30 of them) that are activated by pathogens
○ They have to be cleaved to become activated
○ If they aren’t activated they aren’t useful!
○ Basically a domino effect
What is the complement system?
what are they important for?
Extremely important for inflammation
What is the complement system?
where are they commonly activated?
Commonly activated on the surface of pathogens
What is the complement system?
How many pathways? what result?
There are 3 different pathways that will result in the same end function.
What is the complement system?
what 2 functions?
Has INNATE & ADAPTIVE functions!!!
What is the complement system?
What are the names of the 3 different pathways
classical pathway: antigen:antibody complexes
Lectin Pathway:
Lectin binding to pathogen surface
Alternative Pathway:
Pathogen surface
What is the complement system?
what are the end
results of these pathways?
Recruitment of inflammatory and immunocompetent cells
Opsonization of pathodens
Killing of pathogens
Complement system
What are 3 Ways of protection:
Ways of protection:
1. Some components act as
chemoattractants-
a. Recruit phagocytic cells to sites of
comp.Activation (low-> high conc)
2. Complement proteins that bind
covalently to the pathogens
opsonizing them for
phagocytosis
3. MAC!
a. Creating pores in the pathogens
membrane & destroying it
Complement system
Adaptive immunity functions
what does opsonizarion all allow for?
enhancement of what response to do what?
Adaptive immunity functions
● Opsonization also allows for the uptake
of microbes by APC like DC
● Enhancement of B cell response to
complement coated microbes
Rules of the complement :)
Name is based on order of what?
● Named based on order of discovery
C1-C9
Rules of the complement :)
Smaller fragment =?
Larger fragment=?
Except when?
● Smaller fragment= a
● Larger fragment= b
● Exception for C2 the lg fragment is
C2a!!!!!
○ Please know this!
Rules of the complement
what are alternative pathway components called?
● Alternative pathway components are
called factors!
○ Large fragment=b and small= a
Rules of the complement
what does each system result in?
Each system results in a C3 convertase
bound to the pathogen
Rules of the complement
what does C3 cleave?
what result?
explain?
C3 cleaves C4
○ Results in C5 convertase
○ C3b= VERY NB EFFECTOR MOLECULE
(opsonin molecule)
C3a= mediator of inflammation
Rules of the complement
when C5 Cleaved, what result?
C5 is cleaved
○ C5a= inflammatory peptide
○ C5b= results in the formation of MAC
The classical pathway
what are they IgM and IgG?
what happens?
IgM and IgG= activators
○ 1 IgM molecule of several IgG molecules
bind to an AG and the Fc portion of the
AB binds to the C1 molecule
The classical pathway
C1 has __?_ segments
C1 has 1q,r,s segments
The classical pathway
C1 is activated when what?
C1 is activated when 2 globular heads of
the C1q bind to the Fc region of the AB
that is bound to the AG.
The classical pathway
C1q activation causes what?
this results in what?
C1q activation activates C1r which
cleaves itself then cleaves C1s
The classical pathway
Activates Cls cleaves to what?
Activates Cls cleaves C4
Classical pathway
C4b attaches to the surface of what and/or what?
C4b attaches to the surface of the
microbe or and AG-AB complex
Classical pathway
C1s cleaves what?
C1s cleaves C2
Classical pathway
C2a binds to C4b and makes what?
C2a binds to C4b(C4b2a complex)
Classical pathway
C4b2a is the classical pathway of what?
C4b2a is the classical pathway of C3
convertase
Classical pathway
C3 contratase cleaves C3
true or false
true
C3 convertase cleaves C3 (obvi)
Classical pathway
C2b binds to what?
C2b binds to c3 convertase
Classical pathway
C4b2a3b = what?
C4b2a3b= c5 convertase
Classical pathway
C5 convertase cleaves what?
C5 convertase cleaves C5
Classical pathway
when C5 convertase cleaves C5
C5b remains what/what result?
C5 convertase cleaves C5
○ C5b remains associated with the
C4b2a3b complex which is NB for MAC
Classical pathway
Fill in the blanks
C1 binds to IgM or several IgG–>
C1q cleaving ___?__–>
C1r cleaves Cls—>
Cls cleaves ___?_
this leades to either:
Cb4 attaching to the surface of _?____
or
Cls cleaving C2 –>
C4b2a= ___?___
(this aids in the opsoniisation 1 goal of comp) —>
C3 contravers=cleaves C3—>
C4b2a3b=____?___ –>
C5b=remains associated with the C5 convertase complex=aids in MAC FORMATION
(see slide 8 for diagram)
C1q cleaves C1r
C1s cleaves C4
C4b2a=C3convertase
C4b2a3b=C5 convertase
The lectin pathway :)
What kind of IR?
what does it bind to?
Independent innate IR!
○ Binds to carbohydrate residues of
paths
The lectin pathway
MBL (sim to C1q) & Ficolins can do what?
MBL (sim to C1q) & Ficolins can
recognize microbial specific carbs on the
surface of microbes
The lectin pathway
MBL = binds to what?
what change occurs?
this promotes what?
MBL= binds to the microbe cell wall and
an conformational change occurs which
promotes activation of MBL-associated
serine proteases (MASPs)
The lectin pathway
MASP’s cleave what and what?
MASPs cleaves C4, and C2.
The lectin pathway
C4b2a=
C4b2a= C3 convertase cleaves C3
The lectin pathway
C4b2a3b=
initiates what?
C4b2a3b= C5 convertase
○ Initiates MAC
The lectin pathway
fill in the blank:
MBL binds to __?___
–>
MASPS= ____?___
—>
C4b2a3b= __?______
—>
this aids in ______?____
MBL binds to the cell wall
MASP’s = activated and cleaves C4 and C2
C4b2a=C3 conertase
C4b2a3b=C5 convertase
this aids in MAC Formation
The Alternative Pathway
Utilized the nonspecific (this is called what?)
which does what? to C3
Utilized the nonspecific (spontaneous
cleavage) low level hydrolysis of C3
The Alternative Pathway
If C3b binds to a healthy cell mem what happens?
Are these found on microbial membranes and cell walls?
Residues on the membrance promote what?
If C3b binds to a healthy cell mem it is
rapidly degraded due to sialic acid
(which aren’t found on microbial
membranes and cell walls) residues on
the membranes which promote binding
of C3b to factor H
The Alternative Pathway
what is going on with Factor H and Factor I?
Factor H and Factor I inactive and
degrade the inappropriately bound
C3b
○ “HI”PLS DON”T KILL ME*
The Alternative Pathway
where is this occurring?
On the Microbes surface
The Alternative Pathway
C3b binds to Factor B= ?
C3b binds to Factor B= C3bB
The Alternative Pathway
C3bB=cleaved by factor D=?
C3bB= cleaved by factor D= C3bBb
The Alternative Pathway
C3bBb=C3 convertase (cleabes C3)
stabilized by what?
C3bBb= C3 convertase (cleaves C3)
○ Stabilized by factor P
The Alternative Pathway
C3bBb3B= ?
C3bBb3B= C5 convertase
The Alternative Pathway
Cleaves C5= what?
Cleaves C5= aids in the MAC formation
The Alternative Pathway
The alternative pathway on a host cell
Fill in the blanks
C3 spontaneously cleaved
—> ___?__ binds to cell surface
—> binds to __?__ factor
—> factor __?___
—> “hi” please don’t kill me
—-> degrades __?____
C3–> spontaneously cleaved
—>C3b binds to cell surface
—->binds to Factor H
—-> Factor l
—-> “hi” please don’t kill me
—-> degrades to C3b
The Alternative Pathway
On a microbe membrane
fill in the blank
C3b—>
binds to Factor __?__
—> C3bB complex
—> cleaved by Factor ____?
—> C3bBb= ______?__
–> stabilized by Factor P (Properdin)
—-> C3bBb3B= ___?____
MAC
On a microbe mem
c3B—>binds to Factor B
—>C3bB complex
—->cleaved by Factor D
—->C3bBb=C3 convertase
—>stabilized by Factor P (Properdin)
—> C3bBb3b=C5 convertase
—> MAC
* check this C3bBb3b—on the previous slide it was C3bB3B Idk which one is correct.
What is MAC?!?!?!-> Membrane attack pathway
Constructs a protein complex that makes a hole in the target membrane
and kills the microbe
What is MAC?!?!?!-> Membrane attack pathway
C5 convertase initiates the formation of ?
Classical and lectin=?
alternative =?
C5 convertase initiates the formation of MAC
○ Classical and lectin= C4b2a3b/ alternative= C3bBb3b
What is MAC?!?!?!-> Membrane attack pathway
C5b= recruits what to make what
then C8 binds
C5b= recruits c6 and C7= C5b67 then C8 binds
What is MAC?!?!?!-> Membrane attack pathway
what does it result in?
Results in a hydrophobic region
What is MAC?!?!?!-> Membrane attack pathway
10-16 copies of C9= ?
10-16 copies of C9= make a pore
What is MAC?!?!?!-> Membrane attack pathway
?= make a pore
10-16 copies of C9= make a pore