| Comments |
P.1771 left column 2nd paragraph: "To correlate leukocyte retention with cell size, leukocyte diameter was measured in two ways (Table 1, Fig. 2): by use of axial light extinction in the pulse width mode on a flow cytometer (refs 5,34) and with a Coulter counter (ref 40). As measured by flow cytometer, ... lymphocytes (were) the smallest with a mean diameter of 6.05 µm...These results were confirmed by the Coulter counter and did not appear to change significantly when the cells were fixed and dehydrated (Table 1)." This is the optically determined flow cytometry value based on three donors of 11,000 to 70,000 cells per donor. It is NOT the Coulter Counter ~7µm value calculated from impedance-based volume measurements which Downey states have significant problems for this particular cell type (i.e. heavily folded plasma membrane and impedance mismatch to calibrating material). He therefore ignores the Coulter Counter impedance-based volume estimates converted to the ~7µm diameter readings in his Table-1. Optical measurement of the diameter of a spherical cell form is the least convoluted, most practical, and most easily cross-checked against other like-measurements (confer Schmid-Shonbein, 1980, Morphometry of human leukocytes light microscopy - 5.75µm transmission electron microscopy 6.2µm). In summary, Downey places the diameter at 6µm (6.05µm, p1771) based on the average of the three runs of the optical flow cytometer data, with a corresponding volume (calculated) of 110-120µm^3. |