[Cytometry] how to interpret whole population shifts

Stuart Peter Berzins berzins at unimelb.edu.au
Fri Dec 3 06:29:54 EST 2010

Hi all,

We continually come up against situations where the histogram profile of
antigen expression is near-identical in shape to the negative control (be it
unstained sample, isotypes or non-expressing cells). In essence, the whole
population of the test sample shifts slightly to the right so the shape of
the curve is maintained, but on an overlay, the middle of the 'positive'
sample, now aligns with the leading edge of the 'negative' sample. People
disagree about what this sort of data means. My question is how to
interpret/describe the outcome. Should we...

1. Describe the sample as being (as an example) 30% positive for the antigen
in question because a gate starting at the edge of the negative sample takes
in 30% of the test sample?

2. Describe the sample as being 100% positive because the whole population
appears to have shifted to the right (perhaps suggesting the expression of
the antigen is higher.

3. Not express the sample as % positive at all and instead simply describe
the results as shift in the MFI of the population.

Or perhaps we should simply be suspicious of background staing because the
shape of the curve hasn't shifted (in instances where we are not expecting
100% of cells to express the antigen).



Dr Stuart Berzins
NHMRC RD Wright Fellow
Department of Microbiology and Immunology,
The University of Melbourne,
Parkville 3010,
email: berzins at unimelb.edu.au
Ph (office): +61-3-8344-5706
Ph (lab): +61-3-8344-5704
Fax: +61-3-9347-1540
Mobile: 0427 849 123

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