Histiocytosis-X: in situ characterization of cutaneous infiltrates with monoclonal antibodies.

Cutaneous lesions in three cases of histiocytosis-X were studied by light microscopy, electron microscopy, and immunoperoxidase technics. In each case, Birbeck granule-containing histiocytosis-X cells infiltrated the epidermis and were apposed to lymphocytes. The histiocytosis-X cells and normal Langerhans cells stained with anti-T6 and anti-I1 (Ia-like) antibodies but were negative with anti-T3, anti-T8, anti-M1, and anti-lysozyme antibodies. In addition, the histiocytosis-X cells also stained with anti-T4 antibodies, which react with T-cells associated with helper/inducer phenotype. This study supports the hypothesis that histiocytosis-X cells are abnormal Langerhans cells. The presence of T4/T6-positive cells in cutaneous disease may be a marker for abnormal Langerhans cells.