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Old 03-21-2011
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Immunology Anti-id antibody

Hi all,
help me please to make clear some things.

The question: A monoclonal IgG ab directed against the HA of influenza A virus acts to neutralize the binding of the virus to the target cells. A second IgG ab is made against the idiotype region of the first ab, and it inhibits viral infection. Which of the following is most likely recognized by the IgG anti-idiotype ab?

Of course we know that HA works against sialic acid, so correct answer will be "Sialic acid"

Explanation (if you need): An anti-id ab is directed against the portion of the ab that recognized the original antigen and in many ways will resemble the original antigen. Sialic acid is the receptor for influenza virus. Because the original ab prevents the binding of HA to sialic acid, the anti-id won't to HA. Binding to complement is a normal property of IgG. By difinition, the anti-id will bind to the anti-HA, because anti-HA was the immunogen to which the anti-id was made.

My questions: I didn't understand which region of "second" ab has receptor to sialic acid (is it site for binding to FC receptors)? Because if it would be a abtigen-binding site it could be immunologic reacton...
Why we need ABs with "sialic acid" like binding shape? How it can help with influenza infection?
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Old 03-21-2011
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Quote:
Originally Posted by deyneko View Post
My questions:

1. I didn't understand which region of "second" ab has receptor to sialic acid (is it site for binding to FC receptors)? Because if it would be a antigen-binding site it could be immunologic reacton...

2. Why we need ABs with "sialic acid" like binding shape? How it can help with influenza infection?
1. I think the second Ab (Ab2) would recognize sialic acid with its Fab - that's the whole point of Jerne's theory of idiopathic antibodies, right?

2. Maybe to protect the sialic acid from the neuraminidase?
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Old 03-22-2011
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Originally Posted by Mondoshawan View Post
1. I think the second Ab (Ab2) would recognize sialic acid with its Fab - that's the whole point of Jerne's theory of idiopathic antibodies, right?
Hmm.. Not sure. We know that sialic acid presents on surface of human cells erythrocytes (?) and other human's cells for example cells of upper respiratory tract. So why the influenza virus use it for attach (by HA). If an AB attach to sialic acid by FAB site (antigen binding site) - it is means only one - "I found an enemy". A cell marked by an antibody will be destroyed at the end. So we will have immuno reaction in "reumatic fever" style. Do we have something like this during influenza infection? Am I correct?

I just remember info in the qustion explanation: " Binding to complement is a normal property of IgG" - why I thought second AB could attach to sialic acid by FC region looks like it use FC receptor with complement or other immologic cells.

But in the other hand if AB is attached to not immuno cells by FC region and by antigen binding site to antigen what will happen?

I guess all people around know the answer and can explain but smiling and keep silence... Hey people help us! :sorry:
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