CD34+CD38-

Hi everybbody,

recently we have been sorting CD34Fitc positive CD38PerCPCY5.5 negative BM cells 
on a MoFlo. This population although correct in number of recovered cells shows no 
enrichment whatsoever on reanalysis.
This population is part of a 4-way sort. The other 3 populations when reanalysed have 
purities above 95%. (Total colours = 6)
We switched to using PE-CY5 instead of PerCP5.5. and saw the same problem.

Using exactly the same voltage and compensation settings we did a 4-way sort with 
beads and got 100% purities on all populations...which rules out malfunction of the 
instrument.

We reverted back to labelling the CD38 with Fitc and CD34 on PE and found that the 
purities were back to normal i.e. above 90%.

Has anyone come across a similar problem with tandem conjugates? I am reluctant to 
say that aCD38 cannot be used with a tandem conjugate label and would greatly 
appreciate any plausible explanation for this phenomenon.

We are very much aware of the instability of tandem conjugates and the circumstances 
that exacerbate this, the tandems mentioned are purchased from Beckman Coulter - as 
are most of the tandems we work with and on the whole our experience with them is 
good.
regards
Ann