CD1a (LEU6) is an MHC class I-related glycoprotein of the CD1 family expressed on the surface of Langerhans or dendritic cells. CD1A proteins present antigens to T-cells in order to induce an immune response to certain pathogens. In addition to the response to bacterial invasion, CD1a-reactive cells have also found to regulate the immune response in individuals with bee and wasp venom allergies. Likewise, there is evidence that CD1a regulates and amplifies the inflammatory response in a number of inflammatory skin diseases. In immunohistochemistry, CD1A has membranous staining in cortical thymocytes, interdigitating reticulum cells and Langerhans cells. In cancer, CD1A stains positively in thymomas, precursor T-lymphoblastic leukemia or lymphoma, and Langerhans cell histiocytosis X.
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