Abstract. The monoclonal antibody AM-3K, which was developed using human pulmonary macrophages as the immunogen, immunocytochemically labels most human macrophages except for blood monocytes and dendritic cell populations. AM-3K also shows cross-reactivity in some animal species. To evaluate the usefulness of AM-3K, the present study investigated the detailed distribution of AM-3K-immunopositive macrophages in normal and diseased tissues of dogs, cats, horses, cattle, pigs, and rabbits. Zamboni's solution-fixed, paraffinembedded sections were the most available for the immunocytochemistry with AM-3K. In all animal species examined, AM-3K labeled most macrophages in splenic red pulp, lymph node sinuses and thymus, and tissue macrophages in the interstitium of various organs and sites such as the kidneys, lungs, heart, pancreas, intestines, and skin. Alveolar macrophages and perivascular microglial cells were also immunoreactive for AM-3K. Interestingly, Kupffer cells of dogs, cats, and horses were labeled for AM-3K, but those of cattle, pigs, and rabbits were not. Furthermore, in tumor tissues and inflammatory lesions such as liver fibrosis and encephalomalacia that were obtained from dogs, infiltrating macrophages were stained with AM-3K, but not all infiltrating macrophages reacted to AM-3K. In addition, only 30-50% of pulmonary and peritoneal macrophages obtained from cats and dogs were reactive for AM-3K. AM-3K did not react with blood monocytes, dendritic cell populations, and osteoclasts. These observations indicate that AM-3K specifically labels most exudate and tissue macrophages in the animal species examined. However, the expression of antigens recognized by AM-3K on macrophages may be dependent on differential maturation stages or different functions evoked by some conditions. AM-3K immunoreaction products were seen on the cytoplasmic membrane of macrophages by immunoelectron microscopy. AM-3K would be useful for detection of macrophage populations in the animal species examined here.

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A cell line (KMY-J) was established from a transplantable tumor (MM-KMY) derived from a spontaneous malignant meningioma arising in an aged F344 rat, and three cloned cell lines (KMY-1, KMY-2 and KMY-3) were induced from the parent KMY-J. Morphologically, KMY-J and tumors induced in syngeneic rats by KMY-J showed cell pleomorphism. All neoplastic cells in KMY-J and its tumors were immunoreactive to vimentin; occasional cells reacted to ED1 (rat macrophage/histiocyte-specific antibody) and alpha-smooth muscle actin (alpha-SMA), indicating expression of histiocytic or myofibroblastic immunophenotypes of meningioma cells. In contrast, KMY-1, KMY-2 and KMY-3 consisted of a uniform cell population differing from each other. KMY-1-induced tumors were similar histologically to meningeal fibrosarcomas. Dendritic cells seen in KMY-2 cultures gave an appearance of arachnoid trabecular cells. In KMY-3 and its tumors, large round cells and multinucleated giant cells were predominant. Cells of these cloned cell lines also reacted to vimentin, but were negative for ED1 and alpha-SMA. By the bioassay using PC12 cells and reverse transcription-polymerase chain reaction for nerve growth factor (NGF) mRNA, production of NGF was demonstrated in the parent and cloned cell lines. The present cell lines may prove useful for studying the histological features of meningeal tumors and the bioactive factors produced by meningeal cells.

Renal interstitial fibrosis was induced in rats by chronic unilateral ureteral obstruction (UUO). To identify the mechanisms behind the fibrosis, macrophage influx, myofibroblast involvement, and the localization of transforming growth factor-β (TGF-β, a fibrogenic cytokine) were investigated immunohistochemically in rats euthanatized at 0 (controls), 3,6,9,12, and 15 days after UUO. The number of α-smooth muscle actin-positive myofibroblasts began to increase significantly in the medulla from day 3, and the development of medullary fibrosis was confirmed from day 6 by morphometric analysis. From day 9, papillary fibrosis also developed in association with an increased number of myofibroblasts. These myofibroblasts showed a parallel orientation to the mucosal surface of the pelvis. In the medulla and papilla, from day 6 the number of ED1 (primary antibody)-positive macrophages began to increase significantly. There appeared to be a relationship between macrophage influx and myofibroblast involvement. By contrast, in the cortex there was no marked increase in myofibroblasts nor development of fibrotic tissues, regardless of increased number of macrophages from day 6. Immunohistochemically, no staining for TGF-β was found in infiltrating macrophages or myofibroblasts. However, TGF-& b e t a ; was localized on some cortical proximal renal tubules both of normal control and obstructed kidneys in the early stages on days 3, 6, and 9, suggesting that the possible origin of TGF-β may be renal epithelia. However, the staining intensity for TGF-β on the renal epithelia tended to be weakened in advanced obstructed kidneys on days 12 and 15. The likely contribution of TGF-β to the advanced stages of UUO-induced renal fibrosis remains to be determined.

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