Should it be CD64+ and CD34 - And CD 15+ and CD33-

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AML M2 flow cytometry immunophenotype CD34 CD64 CD33 CD15 markers

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Now I have all the information needed to give a clear, accurate answer.

Your notes are correct

Looking at the image, the textbook shows two flow cytometry scatter plots for AML-M2, and your handwritten correction/annotation is accurate. Here's the breakdown:

Plot C (left): CD64 vs CD34

The dot cluster sits in the upper-left quadrant - high CD34, low CD64
The textbook labels this: "CD34 and CD64 positive"
But your annotation correctly questions this, because the dot cluster is clearly CD34+ / CD64- (upper-left = high Y axis / low X axis)

Yes - it should be CD34+ and CD64-

CD64 is a monocyte marker (FcγRI). AML-M2 is a granulocytic/myeloid leukemia with maturation, not monocytic. The blasts are CD34+ (immature stem cell marker retained) but do not express CD64.

Plot D (right): CD15 vs CD33

The dot cluster sits in the upper-left quadrant - high CD33, low CD15
The textbook labels this: "CD33 and CD15 positive"
But your annotation correctly questions this - the cluster is CD33+ / CD15- (upper-left quadrant)

Yes - it should be CD33+ and CD15-

AML-M2 is a blast-predominant leukemia. CD33 is an early myeloid marker expressed on blasts, while CD15 is a marker of more mature granulocytes. Since M2 blasts have arrested maturation, they express CD33 brightly but CD15 is typically absent or only weakly expressed on the blast population.

Summary table

Marker pair	Textbook label	Correct interpretation	Why
CD34 / CD64	"Both positive"	CD34+ / CD64-	CD64 is a monocyte marker; M2 is not monocytic
CD33 / CD15	"Both positive"	CD33+ / CD15-	CD15 marks mature granulocytes; M2 blasts are immature

This is confirmed by NCBI/NBK flow cytometry in leukemia: "AML with maturation (FAB M2) usually expresses MPO, CD11b, CD13, CD15, CD33, and CD65... HLA-DR, CD34, CD38, and CD117 are usually positive." CD64 is specifically listed as a monocytic marker, not a standard M2 marker.

The Quick Compendium of Clinical Pathology also states: "M2 blasts may or may not express CD34, but they are usually positive for HLA-DR, CD13, CD33, CD117, and CD15" - and notably CD64 is not listed as an M2 marker.

Your reading of the dot plots is correct - the textbook labels appear to be inaccurate for those two panels.

Left is y axis line is called positive or negative? I m confused

Great question - this is a very common source of confusion!

How to read flow cytometry quadrants

In a 2-color flow cytometry plot:

X-axis = marker written at the bottom (horizontal)
Y-axis = marker written on the left side (vertical)

Positive = HIGH value = far from the origin (0)

So:

High on Y-axis = Y-axis marker is POSITIVE
Low on Y-axis = Y-axis marker is NEGATIVE
Far right on X-axis = X-axis marker is POSITIVE
Far left on X-axis = X-axis marker is NEGATIVE

Applied to your plots

Plot C (CD34 on Y-axis, CD64 on X-axis)

High CD34 |  [dots here] |
          |              |
Low CD34  |              |
          _______________
          Low CD64    High CD64

The dots are upper-LEFT = CD34 HIGH (positive) + CD64 LOW (negative)

→ CD34+ / CD64- ✓

Plot D (CD33 on Y-axis, CD15 on X-axis)

High CD33 |  [dots here] |
          |              |
Low CD33  |              |
          _______________
          Low CD15    High CD15

The dots are upper-LEFT = CD33 HIGH (positive) + CD15 LOW (negative)

→ CD33+ / CD15- ✓

Simple rule to remember

Quadrant	Interpretation
Upper-right	Both positive
Upper-left	Y+ / X-
Lower-right	Y- / X+
Lower-left	Both negative

So left side of the plot does NOT mean negative - it just means the X-axis marker is negative. The Y-axis marker can still be positive if the dots are high up.

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