Innate immunity

Mike Clark mrc7 at cam.ac.uk
Mon Feb 17 11:55:22 EST 2003


In article <t474a.1162$sv3.220992 at news20.bellglobal.com>, Geronimo
<URL:mailto:user at server.com> wrote:
> 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.
> 
> 

The point I would make is that sometimes it helps not to be blinkered by
dogma but rather to see if the observations are consistent with the
hypothesis.

You say 

'That much AB production requires Ag stimulation, be it T-dependent or
T-independent.'

You are stating that as if it is an absolute fact, whereas I will agree it
is an accepted dogma. However imagine the situation of a germ-free animal,
a specific-pathogen free animal and a hyperimmunised animal. How different
is the total 'immunoglobulin' concentration in each?

Is it true that in the absence of any antigen stimulation no
'immunoglobulin' is ever secreted?

[ It may help if I point out that I use the term antibody for an
immunoglobulin for which I know the antigen. Thus all antibodies are
immunoglobulins, but an immunoglobulin is only an antibody when I know it
is specific for an antigen. Thus immunological semantics raises its head
again! ]

Returning to the original question. Innate immunity is an immune response
that exists prior to any exposure to the antigen. The receptors for the
innate immune system are germline encoded and inherited and expressed in a
ubiquitous fashion. So why can't some antibody specificities be expressed
in the absence of prior exposure to antigen?

Indeed I would go as far as saying that most antibody specificities are
expressed before exposure to antigen, it is just that they are of such a
low frequency in the total population of molecules that we don't see them!
But what if some of these specificities are not of a low frequency?

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




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