Flow cytometry confusion about scatter plot

[Lothric]

Hey,

FA says that the right lower quadrant is empty because all CD8-expressing cells also express CD3. However, the cells in this quadrant are positive for CD8 and negative for CD3.

Isn't that a paradox? If the cells are negative for CD3, how can they say that they express CD3? And why does this have this effect of making a quadrant empty?

See image.

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[HybridEarth]

If you look just at the X axis, you will see that all the CD8+ cells happen to be CD3+ as well. I.e., there are no CD8+ cells that DON'T have CD3+. Only both.

 

[Lothric]

If you look just at the X axis, you will see that all the CD8+ cells happen to be CD3+ as well. I.e., there are no CD8+ cells that DON'T have CD3+. Only both.

Thanks,

The text however says "Cells in right lower quadrant are positive for CD8 and negative for CD3". So this is just "theoretical", and not real, right? There is no light scatter in the right lower quadrant, so there are no actual cells despite the text saying that "the cells are positive for CD8 and negative for CD3 there".

 

[HybridEarth]

Thanks,

The text however says "Cells in right lower quadrant are positive for CD8 and negative for CD3". So this is just "theoretical", and not real, right? There is no light scatter in the right lower quadrant, so there are no actual cells despite the text saying that "the cells are positive for CD8 and negative for CD3 there".

Yeah I think we're on the same page. Their wording isn't the best. What they should have said was, "Right lower quadrant is empty because there are no cells that co-express CD8 and CD3."