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Xifeng Yang
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Date: 2/27/97 7:36 PM
To: cyto-inbox
From: DODONNEL@svherc.ucd.ie
Michelle Fiordalisi wrote
"I calculate % positivity using BD's formula: (Activ. sample - activ. isotype
control) - ( Unstim.
sample - Unstim. isotype control)."
I would be interested in other intracellular flow-ers opinion of this formula:
do you use it
widely?
I have a problem with subtracting the unstimulated sample values. I presume
tnat this is
intended to allow for non-specific intracellular staining that can occur after
permeabilisation.
However, in some ex vivo situations where effector lymphocytes are already
activated a small
percentage of even unstimulated cells may be clearly positive relative to their
isotype control. I
doubt that it would occur in peripheral blood lymphocytes but I have certainly
seen it for IFN-g
in activated BAL cells in pulmonary disease. It occurred in situations where
the clinical disease
was highly active. By subtracting this percentage of cells from that in the
stimulated sample
one might be underestimating the total % of cytokine-expressing cells.
What do the erudite people think?
Dearbhaile O' Donnell,
University College Dublin
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Date: Mon, 27 Aug 1956 20:59:22 +0000 (GMT)
Subject: Re: Intracellular % Formula
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CD-ROM Vol 3 was produced by Monica M. Shively and other staff at the
Purdue University Cytometry Laboratories and distributed free of charge
as an educational service to the cytometry community.
If you have any comments please direct them to
Dr. J. Paul Robinson, Professor & Director,
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