The cells are fixed after FACS Lysis treatment, you could use a lower concentration of formaldehyde, 0.5 or 1%. You can also wash the fixative out after an hour or two and suspend your cells in PBS, the cells will remain in pretty good shape for a few days or longer. Often after formaldehyde fixation the autofluorescence of all cells increases gradually, washing the fixative out prevents this. Best wishes Simon Monard FACS Lab Manager Trudeau Institute Saranac Lake NY12983 Ph 518 891 3080 X352 >>> Lorrie Epling <lepling@medsfgh.ucsf.edu> - 2/14/02 3:37 PM >>> Dear Purdue site: Currently we use a 1:4 dilution of methanol free, EM grade, 10% formalin in PBS as a fixative for immunophenotyping of human blood. We have some preliminary evidence that this concentration is contributing to a decrease in fluorescence for CD45RA Fitc when analyzed at 24 hours. A literature review indicates this is a stronger concentration than the norm (0.5, 1.0 or 2%). Our specimens are processed with either FACS Lysis or Coulter Immunoprep, then fixed. Any opinions or suggestions concerning what concentration best preserves as well as inactivates viral components? Thanks. Lorrie Epling Laboratory Supervisor UCSF/SFGH Core Immunology Lab General Clinical Research Center Phone 415-476-5279 Fax 415-206-8200
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