Eos have highly positively charged granule proteins. FITC has a net negative charge and stains fixed permeabilized human eos stain quite brightly. Eosin (the dye that eosinophils are named after) is actually structurally related to fluorescein and binds to eo for the same reason. I can send you the papers if you'd like. Cytometry 26, pg. 75-76 (1996) Cytometry 36, pg. 77-82 (1999) Other means to identify eos are high autofluorescence and high side scatter after fix/permeabilization. After permeabilization the side scatter of the neuts drops, whereas the eos stays high. Presumably, this is due to the fact that about 50% of the eosinophil content is granule and is essentially solid protein. I think the FITC method is the most robust of the choices. Alexa dyes appear to behave similarly, although we have yet to do definitive experiments. Your mileage with rat cells may differ. Calman _______________________ Calman Prussin Laboratory of Allergic Diseases NIAID/ National Institutes of Health > ---------- > From: Karim Vermaelen > Sent: Tuesday, November 5, 2002 17:00 > To: Cytometry Mailing List > Subject: rat blood eosinophils > > > Hi everybody, > Can anyone recommend an accurate method to count eosinophils in rat > blood using FACS? Someone in our lab is currently doing manual counts > using eosin-treated whole blood... quite excruciating indeed > Thanks for any suggestions! > Karim Vermaelen > > Karim Y. Vermaelen, MD > Dept. of Respiratory Diseases > Ghent University Hospital 7K12ie > De Pintelaan 185 > B-9000 Ghent > > tel +32 9 240 2605 > fax +32 9 240 2625 > e-mail Karim.Vermaelen@rug.ac.be, karimv@mac.com > >
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