Langerin (CD207) staining in normal pediatric tissues, reactive lymph nodes, and childhood histiocytic disorders

Langerin is a recently identified lectin for which antibodies can be used as immunohistochemical markers of Langerhans cells (LCs). We describe the distribution of staining in autopsy pediatric tissues, dermatopathic and other reactive lymph nodes, and childhood histiocytic lesions using the 12D6 antibody (Novocastra). We also correlate CD1a (antibody O1O) staining to these factors. Langerin on epidermal LCs has a coarsely granular cell membrane and a cytoplasmic staining pattern that is always associated with CD1a expression. All 6 skin samples had Langerin(+)/CD1a(+) LCs within the epidermis. Six of 8 thymuses showed single scattered dendritic-shaped cells in the medulla and rare cells within Hassall corpuscles that coexpressed Langerin and CD1a. Cortical thymocytes were CD1a(+)/Langerin(-). Four of 8 livers examined showed a sinusoidal lining pattern of Langerin(+)/CD1a(-). All 15 autopsy lymph nodes showed a similarly strong Langerin(+)/CD1a(-) sinus pattern of staining on fixed tissue elements, mostly in medullary sinuses. All 12 dermatopathic lymph nodes showed accumulation of Langerin(+)/CD1a(+) cells in the pale paracortical nodules. All 24 instances of LC histiocytosis (LCH) were Langerin(+)/CD1a(+). All 12 non-LCH histiocytic disorders are negative for Langerin in the histiocytes of interest. We conclude that Langerin is coexpressed with CD1a on LCs and LCH. Lymph node sinuses and hepatic sinusoids show Langerin(+)/CD1a(-) cells, indicating that, when used alone to confirm LCH infiltration, the 12D6 antibody should be used with caution. At other sites, its diagnostic accuracy is similar to that of CD1a.