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Hello, my name is Dr. Mike Clark.
I was formerly Reader in therapeutic and
molecular immunology in the Department of Pathology, Cambridge University.
This is part of the lecture on antibody structure and function,
this is the second part of that lecture dealing with the functions of antibodies.
In this lecture, we're going to deal with
the structure of the different classes and subclasses of antibody.
In particular, we're going to deal with
the significance of valency in antigen recognition,
and also the role of different classes and
subclasses of antibodies in their immune functions.
Let's return now to something that we were discussing earlier,
the valency of the antibodies for binding antigen.
Essentially lining up these structures, IgG,
IgA, and IgM to use as examples.
As I mentioned before, we've got a monomeric type structure for the IgG,
where we have two antigen-binding sites.
We've got a dimeric structure for the IgA dimer,
where we have four antigen-binding sites.
We've got that pentameric structure
(five repeated subunits) for the IgM,
where we've got 10 binding sites.
We can discuss the valency of IgG as being bivalent,
we can discuss the valency of IgA as being
tetravalent, and we discuss the valency of IgM as being decavalent,
so two valencies, four valencies, ten valencies.
That's the maximum number of antigens that each of these molecules could
bind simultaneously through the Fab arms that are available in individual molecule.
That becomes crucial to an understanding of how these molecules interact with antigen.
What I want to do is to discuss how the valency of the antibody (that