CD11c (also known as Leu-M5 or Integrin alpha X) [5D11] is a member of the leukointegrin family. CD11c is a cell surface adhesion receptor and is predominantly expressed in tissue macrophages, dendritic cells, monocytes, NK cells and granulocytes. CD11c has been shown to be both sensitive and specific for hairy cell leukemia (HCL) (1). CD11c can be used to differentiate hairy cell leukemia from other small B-cell lymphomas (1). Vardiman et al demonstrated that when a bone marrow biopsy showed HCL, virtually all leukemic cells were positive for CD11c (2). In another study, all hairy cell leukemia cases were positive for CD11c and negative for CD5 (3). A panel of CD103, CD11c, CD25, CD5, CD10 and CD23 has been useful in definitively diagnosing hairy cell leukemia (3). Chronic myelomonocytic leukemia monocytes display a population of monocytes with CD11c underexpression which may aid in the diagnosis of chronic myelomonocytic leukemia (4). A panel using CD20 and/or DBA.44 as well as either TRAP, CD11c or Annexin A1 improves specificity when evaluating normal lymphocytes from hairy cells (5).
Dendritic cells play a key role in immunosurveillance. CD11c marks dendritic cells and was evaluated with regard to high-grade cervical intraepithelial neoplasia and prognosis. Specimens with higher rates of CD4+ T-cells, CD11c+ dendritic cells and T-bet+ transcription factors showed a strong correlation with favorable clinical outcomes (6). In a separate study, CD11c positive dendritic cells were dramatically reduced and macrophages were significantly increased in the skin of immunosuppressed renal transplant recipients which may correlate with increased risk of squamous cell carcinoma in these patients (7).