Everything You Never Wanted to Know About
Polarization But Were Afraid You Might Find Out
Most practitioners of cytometry, whether "flow jocks" or
more casual users ("Joe and/or Josie Three-Color"), mea-
sure the intensity of scattered light and fluorescence emis-
sion in one or more selected wavelength regions, and pay
no attention to the degree or direction of polarization of
that light. Most of the time, we have gotten away with it.
However, the article by Asbury, Uy, and van den Engh in
this issue of Cytometry provides incontrovertible evi-
dence that the time has come to pay more attention to
what may be the biggest skeleton in our cytometric closet.
Because the light emitted by most lasers used as light
sources in cytometry is polarized, the light scattered by,
and the fluorescence emitted by, cells are also polarized.
Scattering and emission occur in many directions, over a
large range of angles to the incident beam; the polarized
nature of the scattered and emitted light makes the inten-
sity of detected signals more dependent on the angle and