Antwort: simultaneous screening of 2 cell lines

Richard Haugland richard.haugland at
Thu Mar 21 03:02:49 EST 2002

I suspect that one might be able to do the following:

Separately label the cell populations with calcein AM (or CellTracker Green
CMFDA) but to different levels of brightness by using more or less of the
tracer (or leave one population unlabeled). Both will have green fluorescence
but one should be able to get at least a 10-fold difference in the intensities.
The calcein will leak out of dead cells (a bit less likely in the CMFDA-stained
cells) so it is preferable to label both cell lines. As a dead cell stain I
would also recommend the green fluorescent SYTOX Green stain. Its much greater
intensity in dead cells should make it easy to distinguish dead cells from live
cells even in the presence of other green-fluorescent labels. Of course, one
would have to balance the brightness of both green-fluorescent stains to get
complete discrimination. Alternatively 7-AAD may be suitable for dead cells.
For antigen discrimination a simple R-PE conjugate should then suffice.

Currently there is not a particularly good tracer that can be detected in the
far red with 488 nm excitation, although DiD (DiIC18(5)), which is structurally
analogous to DiC18(3) (which is the structure of PKH26) may be bright enough
even when excited at 488 nm with emission beyond 650 nm.

eug.kreysch at wrote:

> Laird,
> you could possibly use green fluorescent PKH2-GL (FL1) or red fluorescent
> PKH26-GL (Sigma) (FL2) for membrane labeling, respectively, and 7-AAD for
> dead cell exclusion in FL3. Thus, FL1 or FL2 could be used for detection of
> antibody binding.
> Best regards
> Georg
> LBloom at am 15.03.2002 23:10:56
> An:   cytometry at
> Kopie:
> Thema:    simultaneous screening of 2 cell lines
> Hi,
>            I'm looking for a method to label two cell lines differentially
> so
> that they can  be mixed and then tested together for binding to an antibody
> sample and for viability.  The two cell lines differ only by the surface
> antigen to which the antibodies are directed, so the differential labeling
> cannot use a surface antigen.       My cytometer is a FACSCalibur, with
> standard
> optics (488 nm excitation, and detection filters FL1=530/30, FL2=585/42,
> and
> FL3=650LP).
>            A recent paper (Yang, E-P, et. al.  2002.  BioTechniques
> 32:678-682)
> used the dyes CMFDA and CMTMR (Molecular Probes)  for differential cell
> labeling in the FL1 and FL2 channels, and a surface antigen was detected
> with a Cy-chrome fluorophore (BD) in FL3.  Live/dead discrimination was not
> attempted in this paper, and the difference in FL3 signal between positive
> and negative cell lines was not very large.
>             Presumably a cell line labeled with a single dye could be mixed
> with an unlabeled line to achieve the same purpose as using the two dyes,
> leaving one channel available for live/dead discrimination. Does anyone
> have
> an idea for a good combination of fluorophores that would allow me to do
> this with minimal bleedthrough?  It is particularly important that the
> surface antigen fluorophore is well separated from potential bleedthrough
> from the other two dyes, since it will most likely be the dimmest of the
> three signals.
>            Would the following be reasonable:  Alexa 488 in FL1 for the
> surface
> antigen, CMTMR in FL2, and 7-AAD in FL3?  What about CMFDA or BCECF in FL1,
> PE in FL2, and 7-AAD in FL3?  Are there any good generic cell dyes for FL3?
> Any suggestions would be welcome.
> Thanks,
> Laird Bloom
> Phylos, Inc.
> 128 Spring St.
> Lexington, MA  02421
> tel. (781) 862-6400 ext. 253
> fax (781) 402-8813

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