Normal and neoplastic Langerhans cells: phenotypic comparison with other types of macrophages.

The antigenic properties of normal epidermal Langerhans cells and their neoplastic counterparts (histiocytosis X cells) were compared with those of other types of macrophages, by immunohistochemical staining of skin and lymph node biopsies with a panel of mono-clonal antibodies. The phenotype of Langerhans cells, histiocytosis X cells, dermal macrophages and interdigitating reticulum cells were similar (HLA-DR+, OKT 6+/-, Leu3+/-, C3-receptor-, Ig-complex-, R4/23-, MO2-), and differed markedly from those of follicular dendritic cells (HLA-DR-, OKT6-, Leu3-, C3 receptor+, Ig+, R4/23+, MO2-, and histiocytic reticulum cells (HLA-DR+/-, OKT6-, Leu3+/-, C3-receptor+, Ig-complex+, R4/23-, MO2+/-). This indicates that Langerhans cells are related to the interdigitating reticulum cells found in the T cell areas of lymphoid organs, and demonstrates that Langerhans cells do not express C3b, C3bi or C3d receptor molecules. Our data also emphasise that the Leu3 antigen is not restricted to cells of the T cell lineage.