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Difference between revisions of "CD33"

From www.haemtologyetc.co.uk

 
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CD33 is not expressed by mature erythrocytes, platelets, B-cells, T-cells or NK cells. CD33, but is expressed on mature myeloid cells
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CD33 is not expressed by mature erythrocytes, platelets, B-cells, T-cells or NK cells. However, CD33 is expressed throughout myeloid maturation and so is found on mature myeloid cells
 
   
 
   
  

Latest revision as of 15:02, 10 October 2019


  • CD33 is a useful marker contributing to the diagnosis of AML,
  • Less specific than myeloperoxidase and may be less sensitive than CD117
  • There is recognised aberrant expression by primitive lymphoid cells (10-20%)
  • Mature cells of myeloid lineage also express CD33 so gating is essential



Normal expression and function

CD33 is a transmembrane receptor that recognizes sialic acid-bearing glycans It is thought that CD33 functions as an inhibitory protein – supressing signals of the innate immune system. CD33 is strongly expressed on multi-lineage hematopoietic progenitors and myelomonocytic precursors; but is absent from the more primitive pluripotent hematopoietic stem cells. Expression of CD33 is down-regulated on mature granulocytes. CD33 is also expressed on human mast cells and blood basophils.



Diagnostic role


  • Overall around 80-90% of AML will express CD33; it tends not to be expressed in the most immature forms or those with erythroid or megakaryocytic differentiation
  • High CD33 expression may correlate with NPM1 mutation
  • Approximately 10–20% of B lymphoblastic or T lymphoblastic leukaemia/lymphomas may aberrantly express CD33.
  • CD33 can also be aberrantly expressed on some cases of plasma cell myeloma (up to 25%)


CD33 is not expressed by mature erythrocytes, platelets, B-cells, T-cells or NK cells. However, CD33 is expressed throughout myeloid maturation and so is found on mature myeloid cells


Other relevant information:


CD33 has received particular attention as the molecular target of antibody-based treatment strategies in the therapy of AML. Gemtuzumab ozogamicin (GO; Mylotarg) consists of a recombinant humanized anti-CD33 antibody conjugated to a derivative of the cytotoxic antitumor agent calicheamicin.



SUMMARY TABLES


Expression by acute leukaemias and by haematogones

Notes

*In ALL the expression of CD33 is more likely in B-lineage, but is also seen in T-ALL

**In AML CD33 is expressed in around 80% of cases

***In haematogones expression of CD33 is frequent


Expression by B-lymphoproliferative disorders


*CD33 is occasionally expressed in mature lymphoid malignancies, more frequently in B cell types



KEY


The indicated expression frequency, indicates the approximate frequency of occurrence in each particular disease type.


Rare.png

rare (<5%)

Poss.png

possible (5-20%)

Mod.png

likely (20-40%)

Freq.png

frequent (40-80%)

Hi.png

expected (>80%)


Where expression level is unusual or characteristic of a disorder this is indicated by text: