Hairy Cell Marker : CD 103

CD103 (integrin αE) is commonly used as a marker of tissue-resident lymphocytes—particularly CD8+ tissue-resident memory T (TRM) cells and intraepithelial lymphocytes. It binds E‑cadherin on epithelial cells, helping retain immune cells within mucosal and epithelial tissues. CD103 expression also identifies certain tolerogenic dendritic cell subsets in the gut. High CD103 indicates tissue residency rather than circulating cells.

Hairy cell leukemia characteristically shows a B‑cell phenotype: CD19, CD20, CD22 positive, with strong expression of CD11c, CD25, CD103 and CD123. CD200 is often high. Annexin A1 is typically positive (non‑CD marker). It is usually negative for CD5, CD10 and CD23 on flow cytometry, which helps distinguish it from other B‑cell leukemias.

Yes. Classic hairy cell leukemia typically shows strong, bright CD20 expression on malignant B cells. This immunophenotype aids diagnosis alongside markers like CD11c, CD25 and CD103, and supports use of anti‑CD20 therapy (e.g., rituximab) in selected cases. Variant hairy cell leukemia may have a different marker pattern but usually remains CD20 positive.

The classic triad of hairy cell leukemia is: (1) splenomegaly, (2) cytopenias—most notably pancytopenia with marked monocytopenia, and (3) the presence of characteristic “hairy” B‑lymphocytes in peripheral blood and bone marrow (often TRAP‑positive and CD25/CD11c/CD103 positive). Diagnosis uses blood smear morphology, immunophenotyping and bone marrow biopsy; splenomegaly may be massive.

CD103 (αE integrin) is expressed primarily on intraepithelial lymphocytes and tissue-resident memory CD8+ T cells in mucosal and epithelial tissues (gut, skin, lung), where it binds E‑cadherin. It is also found on a subset of dendritic cells in the intestinal mucosa and on certain mucosal CD4+ Tregs and leukocyte populations involved in local immune surveillance and tolerance.

CD markers vary by leukemia type. B‑cell ALL typically shows CD19, CD10 and CD20; T‑cell ALL shows CD2, CD3, CD5, CD7. AML commonly expresses myeloid markers CD13, CD33, CD117 and often CD34 in blasts. CLL characteristically has CD19 with aberrant CD5 and CD23 (CD20 dim). CD34 marks hematopoietic stem cells/blasts; flow cytometry is used for diagnosis.