APC detection anomaly
pal.jakso at aok.pte.hu
Thu Nov 24 08:14:56 EST 2005
To set up a new compensation matrix I used BD Compbeads stained with
different florochrome conjugated antibodies. Unfortunately I
experienced very strange result in the APC channel.
First I tried to measure positive beads stained with CD7 APC antibody
and I surprised because only a fraction of the events showed
positivity with APC. Previous to this I adjusted the gain using
negative unstained beads so that the events took place at the 1st
quadrant of the four decade axis. I used the antibody in the
concentration what the manufacturer suggested.
I could reproduce this anomaly with T-lymphocytes too. I stained a
blood sample with CD2 PE, CD3 PE-Alexa700 and CD7 APC. The ratios of
the CD2 and CD3 positive cells were the same but the CD7 positive
ratio was lower significantly (19 percent of the CD2/CD3 positives).
Then I stained this sample with CD2 PE and CD7 FITC and the ratio was
Second, as I lowered the gain for the FL4 channel the ratio of the
positive beads decreased! I've never seen such a thing before.
I checked the beads with FITC staining and 99,5% of them were
positive in addition adjusting the gain didn't modify the ratio of
the positive events in the FL1 channel.
Had anybody such an experience before ? Something may be wrong with
the photomultiplier ?
University of Pecs
Faculty of Medicine
Dept. of Pathology
12. Szigeti str.
H-7643 Pecs, HUNGARY
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