Annette Byrne wrote: > Hello all > > Does anyone have an info on relative sizes of the following cell types: > Fibroblasts, endothelial cells, smooth muscle cells and macrophages. I am > trying to make a gross distintion of a mixed cell population containing the > cells above based on their FSC/SSC. > > If anyone could order them based on largest to smallest cell type I would > be eternally grateful ! > FSC does not measure cell size!!!!!!!! In some instruments, 5.5 um plastic beads have bigger FSC signals than 5.0 um plastic beads (and in other instruments, they don't). These beads are relatively uniform and smooth-surfaced and spherical, and all have pretty much the same refractive index; FSC (and SSC) signals are influenced by both size and refractive index. The refractive indices of cells, by contrast, vary with the cells' content of water and of proteins and other macromolecules. If you can't reliably use FSC to tell that a large lymphocyte is bigger than a small one, you certainly can't use FSC to compare relative sizes of different cell types. If you happened to have access to pure populations of the cell types you were interested in, you could produce FSC vs. SSC plots for each, which might help in resolving a mixture, provided the cells in the mixture had not been exposed to conditions that could change their refractive indices or sizes. The best way to identify mixed cell types on FSC vs. SSC plots is to gate individual cell types based on the presence of a specific marker, but you have to be sure of the marker specificity - see my reply to a posting from Ray Hester on reticulocytes. And, as far as sizing goes, while Coulter volume has its problems, it's far more accurate than scatter measurements. -Howard
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