Expression of Mononuclear Phagocyte Antigens in Histiocytic Sarcoma of Mice

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Abstract
Twenty cases of histiocytic sarcoma in 15 female and five male (384 to 722 days of age) hybrid F1(C57BL/6 x BALB/c) or F2(F1 x F1) mice were studied for expression of mononuclear phagocyte and other antigens. Histiocytic sarcomas were found most often in liver, uterus, spleen, and lung. Tissues fixed in Bouin's fluid provided preservation of antigen immunoreactivity, using avidin biotin peroxidase complex immunohisto-chemistry, with monoclonal and polyclonal antibodies. The mononuclear phagocyte antigens, lysozyme and Mac-2 (a galactose-specific lectin that binds IgE), were found in 60-70% of the cases. The receptor for the macrophage colony-stimulating factor (CSF-1), c-fms, was expressed in 2/20 (10%) of the cases. Mouse immunoglobulins were not found in histiocytic sarcoma cells. In uterine histiocytic sarcomas, previously reported as Schwannomas because of their histologic appearance, S-100 protein was not expressed by tumor cells, although they usually expressed Mac-2 and lysozyme. Hyaline droplets were found in the renal tubules of only 2/19 cases. Our studies provide evidence that murine histiocytic sarcoma expresses antigens (Mac-2, lysozyme, c-fms) found in cells of the mononuclear phagocyte series, in contrast to the B-cell origin of many human histiocytic tumors.