Normal Blood and Marrow- Progenitor and Myeloid

Question 1

What is the immunophenotype of uncommitted

Hematopoietic stem cells ?

Answer 1

• CD34
• HLA-DR (dim)
• CD133

IMP: as the cells mature and differentiate they gain CD38 (activation marker)

• many HSC are quiescent and do not divide (no Ki677) and don’t gain CD38

Question 2

What are the normal percentages of progenitor cells

within the bone marrow ?

Answer 2

• CD34: 1-2%
• CD117: 2-4%
  
  • this marker is expressed beyond the progenitor cells

***be careful of regenerating bone marrows that can have more than this.

Question 3

What is a pitfall of often seen in regenerating marrows,

or in patient’s who receive G-CSF therapy ?

Answer 3

• CD56 can be expressed on the graunlocyte and monocyt precursors

Question 4

What is the pattern of expression of CD45

in stem cell precursors ?

Answer 4

• CD45 (pan-leukocyte antigen)
  
  • dim in marrow precursor cells including myeloblasts, monoblasts, precursor B cells and erythroblasts
  • bright on mature cells
  • negative in erythroid precursors

Note: CD13 is a marker of early myeloid maturation.

Question 5

What are the normal markers of progenitor populations

found in the bone marrow ?

Answer 5

• CD34+// CD117+// CD45(dim)// CD13 +
  
  • Normal myeloid/monocytic progenitor population
• CD34+// CD117-// CD45(dim)// CD13-
  
  • Normal precursor B-cell population
    
    • would need additional B cell lineage markers

Question 6

What cells are considered part of the

myeloid lineage ?

Answer 6

• Neutrophils
• Eosinophils
• Basophils
• Monocytes
• Erythroids
• Megakaryocytes
• Mast cells
• Dendritic cells

Question 7

In what populations, other than progenitor cells,

is CD34 brightly expressed ?

Answer 7

• committed normal lymphoid and granulocyte-monocyte precursors
• CD34 is then lost with further differentiation
  
  • similar finding with HLA-DR
• Myeloblast
  
  • CD34+// HLA-DR +//CD117+
  • Note: CD117 is expressed into Promyelocytes, but lost in Myelocytes

Question 8

What cells is CD117 positive in ?

Answer 8

• Myeloblast
• Promyelocyte
  
  • CD34-// HLA-DR -// CD117+

Note: Mast cells will also be positive for CD117.

Question 9

What is the maturation pattern seen in myeloid

lineages with CD13 and CD33 ?

Answer 9

• CD13 and CD33 increase in intensity on myeloblasts up until the promyelocyte stage
  
  • Then the intensity wanes but is still positive as the cells mature into neutrophils
• Monocytes**
  
  • CD13 and CD33 show a continual increase in intensity

Question 10

What are late antigens that appear during the

myelocyte-neutrophil stage ?

Answer 10

• CD15 - first appears during the late promyelocyte stage
• CD11b- also late promyelocyte stage
• CD10 and CD16 - expressed from metamyelocyte-band stage
  
  • IMP: sometimes these markers can be used to ID sepsis

Question 11

What is the phenotype of mature neutrophils ?

Answer 11

• CD45+// CD13+// CD33+// CD11b+// CD15+// CD16+

Note: CD64 may be expressed on early myeloblasts but disappears beyond this stage

• CD64 when seen on neutrophils may indicate sepsis
• CD64 seen in promyelocytes and myelocytes

Question 12

How is the expression of HLA-DR different in early

monocytes compared to myeloid cells ?

Answer 12

• HLA-DR expression is present throughout monocytic differentiation
  
  • in contrast it stops at the promyelocyte stage for myeloid precursors

Question 13

What is the pattern of CD4 expression in monocyte maturation ?

Answer 13

• CD4 becomes acquired at the promonocyte stage
• Normal monocytes retain dim CD4
• this is similar to CD64 and CD11c
• CD14 becomes brightly expressed in the mature monocyte stage

Question 14

What are three markers that are useful for

identifying a monocytic lineage ?

Answer 14

• CD4
• CD64
• CD14

Note: CD64 can be seen on myeloblasts (early), dendritic cells, and activated neutrophils

Question 15

CD15 is expressed on what populations of cells ?

Answer 15

• expressed on both neutrophils and monocytes