In several recent experiments, CD34+ CD38 negative PKH-bright blood cells
were sorted and put into culture. We used a PerCP-labeled antibody (HPCA2, I
think) against CD34. After 24 hours in culture, the cells were reanalyzed by
restaining with the same antibodies used in the original sort. Surprisingly,
half of the cells had become CD34 negative (even though all cells remained
CD38 negative and PKH-bright).
Biologically, this makes little sense because it is unlikely that
quiescent 38 negative cells could have differentiated that quickly. Thus, we
are looking for a fIow artifact. Is it possible that the CD34 epitope could
have been blocked by HPCA-2 antibodies from the original sort? This
explanation requires that PerCP dissociated from the antibody or
photo-bleached. Is this possible? If this explanation is correct, can we
use a different anti-CD34 antibody directed against a different epitope? In
other words, can the CD34 protein be labeled simultaneously at two epitopes?
Thanks for your thoughts!
Doug Dooley
American Red Cross
Portland OR
DEEKEWB@AOL.COM