-----Original Message-----
From: Michel Canton [SMTP:mcanton@wcube.fr]
Sent: Thursday, September 18, 1997 12:14 AM
To: Bob Ashcroft
Cc: cytometry@flowcyt.cyto.purdue.edu
Subject: RE: Cell surface receptor
Dear Bob (Ashcroft),
I fully agree with your comments about my statement on radio-binding being a
gold standard. This implies radio-binding is operated with homogenous cell
lines expressing a single class of specific binding sites. In case of a
doubt, Scatchard analysis may ascertain the point.
Also one has to ensure high level of cell viability (I recommend over 90
percent assessed with Trypan Blue test). In addition non-specific binding
should be determined using control tubes containing excess amount of
unlabeled ligand.
I agree with Bob that radio-binding only provides a bulk reporting response
I consider that this response should be compared to the mean fluorescence
intensity (corrected from background obtained using an irrelevant isotype
monoclonal antibody at a matched concentration).
An example of comparison between radio-binding and quantitative flow assay
of MDR molecules can be found in Cytometry, 23: 120-125, 1996 (Ferrand VL et
al).
I take the opportunity to correct a misstyping that appeared in the part A
of my answer:
Instead of "A recent study from Wagner et al (....) showed that even when
the target antigen is expressed ......"
one should read "A recent study from Wagner et al (....) showed that when
the target is expressed .....".
It seems to us that the word "even" was missleading.
Part B of the answer is coming.
Philippe Poncelet, PhD
BioCytex
France