A transplantable tumor line (KB) was established in syngeneic rats from a naturally occurring sarcoma that had arisen in the thymus of a 24-month-old male F344 rat. Further, a cell line (KB-P) was induced from KB and a cloned cell line (KB-D8) was isolated from KB-P. The primary thymic tumor and KB tumors showed heterogeneous histological growth patterns such as sheet-like, ill-defined bundle, fascicular and interwoven fashions, consisting of spindle cells, oval cells and histiocytic large round cells. Immunohistochemically, neoplastic cells in KB tumors and KB-P and KB-D8 cultures reacted to vimentin and were labeled with antibodies of OX6 (for rat major histocompatibility complex class-II antigens), ED5 (for rat follicular dendritic cells; FDCs) and RED-1 (for interdigitating dendritic cells) in varying degrees, indicating that neoplastic cells exhibited the immunophenotypes of rat dendritic cells. In addition, neoplastic cells were immunoreactive to ED1 (for rat monocytes/macrophages) and ED2 (for rat tissue macrophages), and also showed positive reactions to histiocytic lysosomal enzymes such as acid phosphatase and non-specific esterase. Ultrastructurally, neoplastic cells had cell surface projections, cisterna-like structures and variously developed lysosomes in the cytoplasm. Based on these findings, the present tumor was regarded as dendritic cell-derived sarcoma capable of expressing macrophage-like and histiocytic nature. A reverse-transcription polymerase chain reaction method revealed that the addition of lipopolysaccharide dose dependently increased the expression of mRNA of transforming growth factor-beta1, a proinflammatory factor, in KB-D8 cells. The transplantable line (KB) and cell lines (KB-P and KB-D8) may become useful tools for studying the histogenesis and pathobiological functions of dendritic cells.

Abstract. We examined the morphologic characteristics of pulmonary macrophages in 42 specimens of Odontoceti (Globicephala macrorhynchus, Grampus griseus, Tursiops truncatus, Stenella attenuata, Stenella coeruleoalba, Berardius bairdii), using light and electron microscopes as well as immunohistochemistry with SRA-E5. SRA-E5-positive alveolar macrophages and pulmonary interstitial macrophages contained graphitic soots, indicating the clearance of airborne, aspirated foreign bodies. Pulmonary intravascular macrophages (PIMs), positive with SRA-E5, were present within pulmonary capillaries, attaching to applied endothelial cells by cell junctions. They showed cytoplasmic tubular structures of micropinocytosis vermiformis and erythrophagocytosis, indicating their contributory role in the clearance of blood-borne particles. The uptake of pathogens by PIMs may be associated with the inducement of acute lung injury, especially bacterial infectious pneumonia. This study revealed for the first time the presence of PIMs in cetaceans.Key words: Cetaceans; lung; morphology; pulmonary intravascular macrophage.Pathogens flowing in the blood stream, such as bacteria and endotoxins, aged erythrocytes, and cellular debris, are rapidly removed by macrophages. According to the mononuclear phagocyte system (MPS) theory, macrophages are mononuclear cells derived from the bone marrow, are resident cell types in contact with the blood circulatory system, and play an important role in host defenses. 1,21 Interestingly, it has been reported that MPS-derived cells, called pulmonary intravascular macrophages (PIMs), exist within pulmonary capillaries in the order Artiodactyla (cattle, goats, sheep, deer, and swine), in the order Perissodactyla (horses and burros), and in cats. 2,7,21 To our knowledge, however, there have been no reports on PIMs in cetaceans. We examined the detailed morphologic characteristics of resident macrophages in the lungs of cetaceans. This article is the first description of PIMs in cetaceans.We examined lung samples from 42 animals of Odontoceti caught for the purpose of fisheries by small-type whaling or hand-harpoon fisheries off the coast of Wakayama and Chiba prefectures in 2001-2003, Japan. Specimens comprised 16 Globicephala macrorhynchus, 12 Grampus griseus, six Tursiops truncatus, three Stenella attenuata, two Stenella coeruleoalba, and three Berardius bairdii (Table 1). These samples were provided for our study by the National Research Institute of Far Seas Fisheries, Japan. The age class (adult or immature) of animals was estimated on the basis of standard body length measurements. [8][9][10][11][12]14,15 One or two pieces (4 cm 3 ) of lungs were fixed by immersion in 10% neutral buffered formalin and Zamboni's solution and then embedded in paraffin. For light microscopy, sections were stained with hematoxylin and eosin (HE) and Berlin blue stain. The formalin-fixed lung tissues of G. macrorhynchus and G. griseus were postfixed in 1% osmium tetroxide and embedded in epoxy resin. Ultrathin sections wer...

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Basically, dendritic cell-derived sarcomas are characterized by expression of major histocompatibility complex class-II molecules, but the biological properties of the tumor cells remain to be elucidated. Recently, we established a novel transplantable cell line (KB-D8) from a dendritic cell sarcoma found in an F344 rat. In the present study, we investigated immunophenotypical changes of KB-D8 tumor cells and tumor-associated macrophages (TAMs) appearing in relation to tumor development in syngeneic F344 rats. A number of neoplastic cells in 0.5-cm-diameter KB-D8 tumors showed immunoreactions to OX6 (specific for rat antigen-presenting cells), ED1 (for rat exudate macrophages), and ED2 (for rat resident macrophages), and 72% and 11% of the OX6+ cells were double-immunostained with ED1 and ED2, respectively. Interestingly, the immunoreactions to these antibodies were gradually reduced with increasing size of KB-D8 tumors of 1-, 2-, and 3-cm diameter. These findings indicated that immunophenotypes of dendritic cell-derived sarcomas may be changeable depending on microenvironmental conditions in vivo. Many TAMs seen outside KB-D8 tumors reacted to OX6, ED1, and ED2; the numbers of TAMs immunopositive for these antibodies also decreased as the tumor grew. Similarly, the earlier temporary increase and subsequent gradual decrease in ED2+ and OX6+ cell numbers were observed in the spleen and liver of KB-D8-bearing rats. The reverse-transcription polymerase chain reaction showed mRNA expressions of granulocyte/macrophagecolony stimulating factor, monocyte-chemoattractant protein-1, and osteopontin in KB-D8 tumor tissues. Although the functional roles (biphasic roles: suppressing or promoting) of these factors should be investigated further in relation to tumor development, the factors might be partially responsible for the TAM reactions. KB-D8 would be a useful experimental model to investigate the biological characteristics of dendritic cell sarcomas and tumor immunology in the host.

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