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Diagnosis and tests

Immunophenotype

The related article (“Flow cytometry (immunophenotyping)”) explains blood tests. This topic looks closely at the result of flow cytometry, the immunophenotype: in effect, a cell’s “identity card”.

Last updated: ~1 min read
A cell with coloured badges.
Figure 1.A cell’s marker identity card.

01Short answer

An immunophenotype describes which markers a cell carries on its surface and inside. Each cell type has its own “set” of markers: B cells carry CD19, CD20 and CD22; T cells carry CD3, CD5 and CD7; myeloid cells carry CD13, CD33 and MPO; and immature cells carry CD34 and TdT. The immunophenotype of a leukaemia cell shows which lineage it belongs to (myeloid, B or T) and how mature it is. Sometimes leukaemia cells carry an unusual combination; this “leukaemia-associated immunophenotype” helps find the few cells left after treatment. Rarely, a cell carries markers of two lineages (mixed phenotype acute leukaemia).

02Simple explanation

Immunophenotype: the cell’s identity card.

A set of markers shows the lineage.

An unusual combination helps follow-up.

03Scientific explanation

Lineage markers: MPO defines myeloid, cytoplasmic CD3 defines T, and CD19 with CD79a/CD22 defines B lineage.

LAIP: the leukaemia-associated aberrant immunophenotype is the basis of MRD measurement.

04What happens in the body?

A cell identity card

Markers are badges that show what the cell is.

A lineage tree

Myeloid, B and T branches grow from the stem cell, each with its own markers.

A tree branching from a stem cell.
Figure 2.A tree of cell lineages.

A fingerprint

A leukaemia cell’s combination of markers can be as unique as a fingerprint.

A fingerprint made of coloured dots.
Figure 3.A unique marker fingerprint.

05How an immunophenotype is built

Four steps.

Root — Early markers.1RootEarly markers.
Lineage — Branch markers.2LineageBranch markers.
Maturity — Markers change.3MaturityMarkers change.
Match — Lineage identified.4MatchLineage identified.

06Main marker groups

LineageExample markers
ImmatureCD34, TdT
MyeloidCD13, CD33, CD117, MPO
B cellCD19, CD20, CD22, CD79a
T cellCD3, CD5, CD7
CLL exampleCD5 + CD19 + CD23

07Key terms

Immunophenotype
A description of a cell’s markers.
Lineage
The family a cell belongs to.
MPO
Myeloperoxidase, a myeloid marker.
TdT
A marker of immature lymphoid cells.
Mixed phenotype
Markers of two lineages together.

08Key points

  • The immunophenotype is the cell’s identity card.
  • Markers show the lineage.
  • They also show the stage of maturity.
  • An unusual combination helps MRD.
  • Let your doctor explain the report.
  • It is read together with other tests.

09Frequently asked questions

CD20 positive: what does that mean?

The cells carry CD20; this may be considered when choosing some antibody treatments.

Can the immunophenotype change?

Sometimes after treatment or at relapse, which is why it is rechecked.

What does mixed phenotype mean?

It is a rare type; your doctor tailors the treatment plan.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. CD20 positive: what does that mean?

  2. Can the immunophenotype change?

  3. What does mixed phenotype mean?

My questions

12Sources

  1. National Cancer Institute (NCI). Definition: flow cytometry
  2. National Cancer Institute (NCI). Adult ALL treatment (PDQ), patient version
  3. National Cancer Institute (NCI). Adult AML treatment (PDQ), patient version
  4. National Cancer Institute. NCI Dictionary of Cancer Terms: absolute neutrophil count
  5. National Cancer Institute (NCI). Hairy Cell Leukemia Treatment (PDQ®) — Patient Version
  6. MedlinePlus (U.S. National Library of Medicine). Bone marrow biopsy
  7. National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: Philadelphia chromosome
  8. Blood (American Society of Hematology), 2022. Diagnosis and management of AML in adults: 2022 recommendations from an international expert panel on behalf of the ELN
  9. National Cancer Institute (NCI). Childhood Acute Myeloid Leukemia and Other Myeloid Malignancies Treatment (PDQ®) — Patient Version
  10. National Cancer Institute (NCI). Understanding Cancer Prognosis
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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