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  #1  
Old 11-02-2012
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Immunology IgG and IgM and The Complement Pathway

The molecules of IgG required to activate the classic complement pathway is:
A. Half the molecules of IgM required
B. Same as the molecules of IgM required
C. Double the molecules of IgM required
D. Quadruple the molecules of IgM required
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Old 11-02-2012
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i think D) quadruple the molecules of IgM required..........either B or D

coz, igM is pentamer so has 5 binding sites for complement attachment......but i'm not at all sure..

may i know the source of question........thanks
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Old 11-02-2012
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Default my answer :)

C. Double the molecules of IgM required
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Old 11-02-2012
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Dont know the answer
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Old 11-02-2012
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Quote:
Originally Posted by subbi View Post
The molecules of IgG required to activate the classic complement pathway is:
A. Half the molecules of IgM required
B. Same as the molecules of IgM required
C. Double the molecules of IgM required
D. Quadruple the molecules of IgM required
This is a tough question. I realize now that I don't know too many details in immunology But, to activate the classic pathway of the compliment you need the interaction between the antigen and the epitopes which will result in binding of the complement C1 to Fc portion, right? So, if IgM is a pentimer, does it need 5 molecules of C1 to activate the compliment? I don't know. But I think one would be enough. That's why I choose B) Same as the molecules of IgM required.

P.S This is scary!!!
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Old 11-02-2012
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C ... Double that of IgM ... ( googled for it .. And also IgG4 has no role in activating compliment .. Only the other three can activate the classical compliment pathway )
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Old 11-02-2012
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C ... Double that of IgM ... ( googled for it .. And also IgG4 has no role in activating compliment .. Only the other three can activate the classical compliment pathway )
Did you also find the explanation? Because I don;t see any....
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Old 11-02-2012
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@ Teona :Yeah .. There is no explanation anywhere ... ( may be that is why they say IgM is a potent activator of compliment .. If I find any explanation , I'll let you know Teona! )
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Old 11-02-2012
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Originally Posted by Teona View Post
Did you also find the explanation? Because I don;t see any....
It's CC...Goljan did mention it,it's because IgM is a pentamer (can bind 10 antigens at once while IgG binds only 2)
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Old 11-02-2012
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@blade : if that is the logic , shouldn't it make a 4: 1 ratio ???
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Originally Posted by alice View Post
@blade : if that is the logic , shouldn't it make a 4: 1 ratio ???
Logically,It should be but that's what he said & that's how I annotated it in my FA. these are from master Goljan
Just know that IgG to IgM is 2:1
IgM is a better activator of Classic PW than IgG
IgM starts in acute state while IgG is chronic cases
IgM drives the PW upto production of C1-C9 while IgG stops at C3
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@blade..............goljan mentioned it for antigen pal, not for complement.........regarding binding, IgM, a pentamer and is divalent, thus can bind 10 antigens/epitopes, and only 5 complements.........

the answer here is not related to the binding sites or affinity.............they can't be quantified:...........just remember that when every single IgM molecule can activate the complement, >2 IgG molecules are required for the same effect...................so best answer here would be DD..........>2...................this gives the concept that IgM is the most potent activator of complement, but how potent??-cannot be quantified..............2 or less than 2 molecules of IgG can't activate with same potency is a fact seen experimentally.....................
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Quote:
Originally Posted by subbi View Post
@blade..............goljan mentioned it for antigen pal, not for complement.........regarding binding, IgM, a pentamer and is divalent, thus can bind 10 antigens/epitopes, and only 5 complements.........

the answer here is not related to the binding sites or affinity.............they can't be quantified:...........just remember that when every single IgM molecule can activate the complement, >2 IgG molecules are required for the same effect...................so best answer here would be DD..........>2...................this gives the concept that IgM is the most potent activator of complement, but how potent??-cannot be quantified..............2 or less than 2 molecules of IgG can't activate with same potency is a fact seen experimentally.....................
Hey,I don't get your point.you said Goljan mentioned binding to antigens and not complement?I don't get it?it binds antigens to activate the complements right?maybe you should listen to him again.
What's your source for the quadruple IgG pls?
As I said before,it's even more logical for pentagonal IgG not even bi/quadruple IgG
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Originally Posted by blade View Post
Hey,I don't get your point.you said Goljan mentioned binding to antigens and not complement?I don't get it?it binds antigens to activate the complements right?maybe you should listen to him again.
What's your source for the quadruple IgG pls?
As I said before,it's even more logical for pentagonal IgG not even bi/quadruple IgG
sorry pal...........i didn't mean to say you're wrong..........thank you for your information on IgG and complement...............i just meant to say that here the question asks about complement...........IgM would bind 5 complements and 10 epitopes/antigens...............thanx.........
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Originally Posted by subbi View Post
sorry pal...........i didn't mean to say you're wrong..........thank you for your information on IgG and complement...............i just meant to say that here the question asks about complement...........IgM would bind 5 complements and 10 epitopes/antigens...............thanx.........
Noo...you totally got me wrong.just want to know your source because it contradicts what I heard from Goljan.
In his blood transfusion rxn lectures,he said IgM is a better activator of classic PW,cos it takes seconds and drives production of All complements while IgG needs 2 mol. and stops at C3.
Maybe he is wrongAm learning from you buddy
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Quote:
Originally Posted by blade View Post
Logically,It should be but that's what he said & that's how I annotated it in my FA. these are from master Goljan
Just know that IgG to IgM is 2:1
IgM is a better activator of Classic PW than IgG
IgM starts in acute state while IgG is chronic cases
IgM drives the PW upto production of C1-C9 while IgG stops at C3
thanks for the info.......i think i forgot goljan totally
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Quote:
Originally Posted by blade View Post
Noo...you totally got me wrong.just want to know your source because it contradicts what I heard from Goljan.
In his blood transfusion rxn lectures,he said IgM is a better activator of classic PW,cos it takes seconds and drives production of All complements while IgG needs 2 mol. and stops at C3.
Maybe he is wrongAm learning from you buddy
Hey no offense man...............may be you're very talented but I just told what I knew ok?............this is a past question in the exam and for a source, you can see Kaplan micro Pg. 83 Fig I-7-13...........see just before C1.......there's labelled IgM or >2 IgG............this explanation was the one I got from my fren taking Kaplan active classes in the USA last year...............thanx.

sorry if I made you wrong (I didn't mean to)...........you learn from Goljan not me...........i'll not post any questions in this forum if my answers hampers the knowledge of the members..............thanx.......
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Old 11-03-2012
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Some sources may not be available but we've got to share things we know..........
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Old 11-03-2012
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Originally Posted by subbi View Post
Hey no offense man...............may be you're very talented but I just told what I knew ok?............this is a past question in the exam and for a source, you can see Kaplan micro Pg. 83 Fig I-7-13...........see just before C1.......there's labelled IgM or >2 IgG............this explanation was the one I got from my fren taking Kaplan active classes in the USA last year...............thanx.

sorry if I made you wrong (I didn't mean to)...........you learn from Goljan not me...........i'll not post any questions in this forum if my answers hampers the knowledge of the members..............thanx.......
Dude, i mean nothing here but just want to mention. Lots of small details varies from source to source. Why that above guy asked for source. So that he or she may check it out and rectify there doubt and discuss with us here. Thats what we are doing right?
By putting questions you are doing great thing. Helping us to sharpen our knowledge. We all are on same track and no one is superior or inferior in knowledge. As just chill dude and keep posting your questions.
Meanwhile i also wanted to know your questions source. As they are quite scary but seems i will pass that source asking question
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Originally Posted by koolkiller88 View Post
Dude, i mean nothing here but just want to mention. Lots of small details varies from source to source. Why that above guy asked for source. So that he or she may check it out and rectify there doubt and discuss with us here. Thats what we are doing right?
By putting questions you are doing great thing. Helping us to sharpen our knowledge. We all are on same track and no one is superior or inferior in knowledge. As just chill dude and keep posting your questions.
Meanwhile i also wanted to know your questions source. As they are quite scary but seems i will pass that source asking question
Thanx for your queries man and thanx for cooling me down.............hehe........the source for this question: i've already mentioned in the above post with even page numbers...........lol.............this was from my friend........
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