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  1. A multivalent antibody molecule such as Immunoglobulin M Immunoglobulin A etc bind to more than one antigens or epitopes but I am confused about that wheather these multivalent antibodies bind to identical epitopes or can bind to different epitopes? means if one molecule of Immunoglobulin M being pentameric can bind to 10 epitopes at a time the 10 epitopes that it binds Will be identical or can be different..? Confused about that.. 2. And also another Question I want to ask that as Immunoglobulin G,Immunoglobulin D and Immunoglobulin E are monomers but all of them have 2 antigen binding sites so we consider them as Mutivalent antibodies or not and if we cnsider them as multivalent antibodies then what are the Examples of monovalent antibody that Specifically only bind to One antigen molecule or epitope? Because as far as i Have studied Antibody or Immunoglobulin molecule hae specific "Y" structure that contains 2 binding sites. Similarly in this case also want answer that these momomeric ImmunoglobulinsG,D,E each binds to 2 identical antigens or epitopes or can bind to two different epitopes. Means that if Immunoglobulin G is binding to two epitopes these epitopes will be identical or can be different...??? :/
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  • $\begingroup$ Please separate this into two questions. $\endgroup$ – MattDMo Dec 17 '14 at 18:33
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Any one Plasma Cell that is producing antibody is making one kind of Heavy Chain and one Light Chain. In an IgG, there are two heavy chains each associated with a light chain. Together, a heavy and light chain have one epitope binding region - so in toto, an IgG is multivalent because each heavy chain : light pair can bind a single epitope for a total of two.

If a Plasma Cell is making IgM, it still is making only one kind of heavy chain and one light chain. Because they are pentameric, that does add up to 10 binding locations, but as Matt says above, sterically, all of these sites are unlikely to bind at the same time.

This multivalency is important in crosslinking antigens. Crosslinking is required for the original B Cell Recpetors to activate the B Cell, and it is also useful in clumping antigen in a way that it can be eaten by macrophages or otherwise interfering with the function of the antigen.

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Non-engineered IgM (such as is produced in vivo) has the same binding domain on all "arms" of the pentamer. They don't bind to more than one antigen, instead they can bind to multiple copies of the same epitope. Due to steric hindrance, a single IgM molecule generally will not bind at all 10 binding sites.

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