Dear Flowers, We have an investigator who is studying cytokine production in response to mitogenic stimulus. We observe a down regulation of the CD4 molecule ( in surface staining) by 24 hours that renders this population unidentifiable. They are looking at intracellular cytokines, and surface molecules are stained first, cells are fixed, permeabilzed, and then stained for cytokines. Has anyone seen this? We have repeatedly seen a decrease in the fluorescence of CD3 after PHA stimulation, but never to the point where the population can no longer be seen--this has been reported in the literature. Is there another way to identify the CD4 population using this kind of staining protocol? Cells not stimulated have good surface expression of CD4. Thanks in advance. Kathy -------------------------------------------------------------- Kathy Schell Supervisor, UWCCC Flow Cytometry Facility 600 Highland Ave. K4/535 Madison, WI 53792 Voice: 608-263-0313 e-mail: kschell@facstaff.wisc.edu
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