Based on more recent publications, it is now thought that uptake of dextran particles takes place by receptor mediated endocytosis, not pinocytosis (this action can be blocked with antibodies to mannose receptors). For pinocytosis, we use lucifer yellow (Molecular Probes), used in the following article along with an array of other assays for APC function: Dendritic cells use macropinocytosis and the mannose receptor to concentrate macromolecules in the major histocompatibility complex class II compartment: downregulation by cytokines and bacterial products. Sallusto F, Cella M, Danieli C, Lanzavecchia A. J Exp Med. 1995 Aug 1;182(2):389-400. Hope this has helped. Keith Bahjat Graduate Assistant University of Florida College of Medicine Gainesville, Florida kbahjat@ufl.edu Bruce H. Davis, M.D. wrote: > I developed a flow cytometric method for measuring pinocytosis, which was > originally published in Cytometry 7:251-262, 1986 ( how time flies). In > those studies, I saw no evidience of quenching due to dextran-FITC > concentration in the range of 0.1 - 10 mg/ml. However, the fluorescence is > quite sensitive to pH, so you need to be concerned about endosomal > acidification and the use of buffered solutions. As for freezing the > solution, I never tried, so I can't help you there. > > Bruce H. Davis, M.D. > Dept. of Clinical Pathology > William Beaumont Hosp. > 3601 W 13 Mile Rd. > Royal Oak, MI 48073-6769 > USA > > Phone: 248-551-5137 > FAX: 248-551-1262 > > "Fang-Yao (Stephen) Hou" wrote: > > > Hi,fellow flow cytometrists: > > > > I am trying to develop a flow pinocytosis assay using fluorescein dextran > > from Molecular Probe (D-1845). This assay will be used to monitor the > > antigen uptake by dendritic cells. Does anyone here try similar approach? > > Please share with me your sucess. > > > > Currently, I have two questions in mind. The first one is about the > > stability of frozen fluorescein dextran in solution in the event that > > we may prepare several stocks and freeze them. The second one is the > > concern that too much dextran may end up with lower fluorescence. I saw > > this phenomenon once and suspected that either quenching or too much > > dextran outside the cells being like a barrier resulted in the lower > > fluorescence. I would appreciate your help and would like to see any > > references as well. Thanks. > > > > Fang-Yao (Stephen) Hou > > FYHOU@DELPHI.COM > > > >
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