At 2:35 PM -0400 10/17/05, Mitre, Edward (NIH/NIAID) wrote: >[snip] I've been using an >isotype control to set the threshold for positivity. I reasoned that even >if this didn't allow me to define true CD25 positivity, at least the use of >an isotype would allow me to remain consistent in what I defined as CD25 >positive from one experiment to the next. As another naive question to the list: is there any such thing as a TRUE positive cell for a particular antigen? If there is a spectrum of cell surface expression levels, that will be reflected in the data. I would argue that any "cutoff" be taken from some specific biologic endpoint, be it functional studies, transplantation, whatever. Not knowing a whole lot about the described experimental system, I can't comment much more than that... -J -- J Thompson, M.D. jamest@mail.med.upenn.edu Research Associate, Hematology-Oncology Division University of Pennsylvania 421 Curie Blvd. Philadelphia, PA 19104Received on Wed Oct 19 14:58:00 2005
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