In article <397769DE.4AE2861B at shef.ac.uk>, Tom Barr
<URL:mailto:mdp96tab at shef.ac.uk> wrote:
> Russ,
> I assume your talking about determining titre by ELISA, and if so I
> offer the following advice. Titres will vary wildly between tests as
> conditions are never the same and different scientists will perform the
> tests with slight differences. Different antigens could also be in use
> (and certainly different batches). Values are normally obtained from a
> comparison with normal (non immune) serum (i.e. a titre of 256 would
> indicate the dilution at which experimental sera has a Ig level
> comparable to normal serum). In this case you guess correctly; the
> standard varies.
> It would only be possible to convert a titre to an actual
> concentration if a positive control of known concentration was included
> with each test. This is in unlikely, unless you have a mAb or quantified
> antiserum against the antigen, and at best would give only an approximate
> value.
> Hope that was of some use...
>> Cheers,
>> Tom
I agree with Tom but would add the following.
Antibodies in the blood vay by both concentration and by affinity/avidity.
Indeed because they are polyclonal they will have a range of
concentrations at a range of affinities. On top of this there will be
different classes and subclasses which will vary in the ways they are
detected in most assays used.
The measured titre is a functional integral of the all the above and
without measuring or guestimating several variables at the same time it is
virtually impossible to convert a titre to a concentration. On the other
hand the measured titre can in some instances give a good estimate of the
functional ability of an antisera to recognise or neutralise an antigen.
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
