Well, I have exaggerated in saying "secondary rather than primary". But the
fact remains, there is enough anti(ABO) AB in the serum to agglutinate donor
RBCs in the first incompatible blood transfusion. That much AB production
requires Ag stimulation, be it T-dependent or T-independent. Where does the
Ag come from? If those antigens were present, for example, on the surface of
a pathogen then a secondary IR wouldn't even be necessary against such a
pathogen because the ABs would efficiently neutralize it upon entering the
blood flow. What's so special about the ABO antigens then (AB titres high
enough in the *absence* of the Ag)? We don't know.
"Mike Clark" <mrc7 at cam.ac.uk> wrote in message
news:ant171441345Pk=+ at mrc7acorn1.path.cam.ac.uk...
> In article <o464a.961$mZ2.234059 at news20.bellglobal.com>, Geronimo
> <URL:mailto:user at server.com> wrote:
> > I would also say your question is very interesting, thought for a
> > different reason. I agree with Mike that AB-based immune responses fall,
> > by definition, in the 'adaptive' class. I don't think there is ever an
> > 'adaptive' response without an 'innate' response as well.
> >
> > The ABO antigen example highlights one of the many inconsistencies in
> > Immunology. Although one could argue that anti-ABO ABs are expressed for
> > some reason in every individual, the current paradigm cannot explain
why,
> > in case of a blood transfusion with an incompatible blood type, the
> > immune response has the characteristics of a secondary rather than a
> > primary response. Unless the same antigens are present in some very
> > common pathogens, but that remains to be shown.
> >
>> What of pregnancy?
>> A comparison of the immune response to RhD and to ABO mismatches shows
that
> the former can be a problem during pregnancy whilst the latter normally is
> not. The observation is that the the immune response to RhD exhibits
> affinity maturation and class switching to IgG, which can then cross the
> placenta, whilst the anti-A and B responses remain as low affinity IgM.
>> So I don't regard the immune response to ABO as exhibiting a secondary
type
> immune response. The titres of antibody to A and B remain pretty much
> constant throughout life which is why I am happy to view them as sharing
> properties with components of the innate immune system such as Mannose
> Binding Protein.
>> Mike <URL:http://www.path.cam.ac.uk/~mrc7/>
> --
> M.R. Clark, PhD. Division of Immunology
> Cambridge University, Dept. Pathology
> Tennis Court Rd., Cambridge CB2 1QP
> Tel.+44 1223 333705 Fax.+44 1223 333875
>
