IgG - IgG interactionS...

Mike Clark mrc7 at cam.ac.uk
Fri May 21 07:07:04 EST 1999

In article <374404ce.104432716 at news.club-internet.fr>, Emmanuel-
<URL:mailto:nony at club-internet.fr> wrote:
> Anyone has some information on the nature of the interactions between IgG.
> I have seen papers describing Fab-Fab and Fab-Fc connections but not much
> details on the nature of these interactions unfortunately...
> Are these interactions really specific such as anti-antibody or
> anti-denatured antibod y ? Is there a constitutive expression of anti-IgG
> in mammalian ?
> => Thanks for help or suggestion regarding where to find information ! Reply @ :
> nony at club-internet.fr

There are various well established ways in which antibodies can interact
with each other.

1) Idiotype / anti-idiotype whereby the Fab (V-regions) of one antibody
binds to the Fab (V-regions) of another. The fact that antibodies have
variable sequences makes for endless possibilities of such interactions.

2) Fab to  Fc interactions is seen for several types of antibodies
occurring naturally in vivo. For example anti-allotype antibodies may
recognise allotypic variation in the constant regions of some classes.
(Such antibodies are frequently observed in transfused patients).
Another example is Rheumatoid factors, these are present in many normal
individuals but may be at raised levels in some diseases.
Characteristically they are low affinity antibodies (often IgM) specific
for the constant regions of other classes (often IgG). They may play a role
in complement activation and in clearance of immune complexes of IgG and

3) Fc to Fc interactions. Some subclasses in some species such as IgG3 in
the mouse and IgG2c in the rat have been shown to form self aggregates
stabalising immune complexes or causing cell agglutination. This appears to
be a feature of 'sticky' patches on the CH3 domains of these antibodies.

4) CHO to Protein. Many (most) antibodies are glycosylated, sometimes in
the V-regions (~10% IgG). Thus their is the potential for antibodies to
form aggregates through interactions between the carbohydrate on one
antibody molecule and protein surfaces on another.

5) Disulphide bond exchange. There is some evidence that IgG4 in humans can
undergo disulphide bond exchange in the hinge region with other IgG4
molecules thus excanging half-subunits.


Mike Clark,                        <URL:http://www.path.cam.ac.uk/~mrc7/>
 o/ \\    //            ||  ,_ o   M.R. Clark, PhD. Division of Immunology
<\__,\\  //   __o       || /  /\,  Cambridge University, Dept. Pathology
 ">    ||   _`\<,_    //  \\ \> |  Tennis Court Rd., Cambridge CB2 1QP
  `    ||  (_)/ (_)  //    \\ \_   Tel.+44 1223 333705  Fax.+44 1223 333875

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