CD33expressing

CD33expressing refers to cells that display the surface receptor CD33. CD33, also known as Siglec-3, is a member of the sialic acid-binding immunoglobulin-like lectin (Siglec) family. It is a transmembrane glycoprotein with immunoreceptor tyrosine-based inhibitory motifs that modulate signaling in myeloid cells.

Expression pattern: In humans, CD33 is primarily expressed on cells of the myeloid lineage, including monocytes, granulocytes, and many myeloid dendritic cells. It is commonly found on blasts in many cases of acute myeloid leukemia (AML) and certain myelodysplastic syndromes, but is generally absent from normal hematopoietic stem cells and mature lymphocytes.

Clinical significance: CD33expression is used as an immunophenotypic marker in diagnostic flow cytometry and immunohistochemistry to characterize myeloid leukemias and related disorders. It has therapeutic significance; CD33-targeted treatments, such as antibody-drug conjugates and other experimental approaches, aim to deliver cytotoxic agents specifically to CD33expressing cells. These strategies can effectively target leukemic blasts but may also affect normal myeloid cells, with associated hematologic toxicity. Ongoing research explores CD33-directed therapies including bispecifics and CAR-based approaches, as well as considerations of expression level and heterogeneity.

Limitations and variability: Not all AML blasts express CD33, and expression levels can vary among patients and over time, potentially influencing treatment response and prognosis. Detection typically relies on flow cytometry or immunohistochemical staining in conjunction with other markers.