Immunohistochemical characterization of two new monoclonal antibodies (LN-4, LN-5) reactive with human macrophage subsets and derived malignancies in B5-fixed, paraffin-embedded tissues.

Two monoclonal antibodies (LN-4, LN-5) reactive to human macrophages in B5 formalin-fixed, paraffin-embedded tissue sections have been produced by using deparaffinized cell extracts of peripheral blood mononuclear cells. Both monoclonal antibodies were initially identified on paraffin-embedded sections of hyperplastic lymph nodes by using the immunoperoxidase staining procedure. Specificity screens on normal human tissues show that LN-4 and LN-5 stain the cytoplasm of macrophages and histiocytes in hematopoietic organs including Kupffer's cells of the liver and Langerhans' cells of the skin. LN-4 also showed strong positivity with acini of the stomach, whereas LN-5 was positive with mantle zone B lymphocytes of the lymph node and spleen, spermatogonia, and chief cells of the stomach. Both antibodies were strongly reactive with cases of true histiocytic lymphoma but, except for infiltrating macrophages, were entirely negative in Hodgkin's disease and non-Hodgkin's lymphomas. In all cases of nodular sclerosis Hodgkin's disease, LN-4 was positive in macrophagelike cells present in the collagen bands surrounding the Hodgkin's lesions. Both monoclonal antibodies were also positive in macrophages and histiocytes present in a variety of benign lymphoid lesions including persistent generalized lymphadenopathy, Gaucher's disease, sinus histiocytosis, and dermatopathic lymphadenopathy. Because of their specificity for human macrophages, and their ability to stain B5-fixed, paraffin-embedded tissues, LN-4 and LN-5 are important new reagents for the diagnosis and classification of malignant and benign histiocytic lesions.