Scavenger receptor-mediated endocytosis of chemically modified-low density lipoprotein (LDL) by macrophages or macrophage-derived cells has been intensively studied from the potential link to atherosclerosis. Taking the advantage of the fact that maleyl albumin is also endocytosed via the same receptor, we have investigated the ligand specificity of this receptor by using rat peritoneal macarophages and sinusoidal liver cells. Maleylation of albumin of >50% of its lysine residues resulted in a threshold increase in the ligand activity, whereas demaleylation of maleyl-albumin to 20% did not affect the ligand activity, suggesting that maleylation of selective lysine amino groups of albumin may lead to the formation of the domain structure required for the receptor recognition. To further minimize the ligand domain, five albumin peptides isolated from cyanogen bromide-cleaved albumin were maleylated and determined for their ligand activity. The result demonstrated that albumin peptides with 102 amino acids but not with 37 amino acids gained the ligand activity upon maleylation, suggesting that generation of the ligand activity does not require a whole molecule, but rather, the domain itself might be regional. We next compared maleylalbumin with demaleyl-albumin in their cellular binding and endocytic degradation. Amounts of intracellular degradation of maleyl-albumin were proportionally increased up to a certain level. However, a further increase in cell surface-bound ligands did not affect the subsequent intracellular degradation. Based on these data, we would propose the ‘two binding sites’ model, where two binding sites on surface membranes are involved in the scavenger receptor-mediated ligand recognition; one is specific for the ligand domain and coupled to subsequent intracellular degradation and the other serves a binding site for polyanionic compounds.

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High density lipoprotein (HDL) is known to participate in the removal of free cholesterol from cholesterol-loaded cultured macrophages. To provide some morphological evidence to this phenomenon, endocytic uptake and intracellular pathway of HDL in rat petironeal macrophages were investigated at the electron microscopic level. A horseradish peroxidase conjugate of HDL (HDL-HRP) showed specific binding to coated pits of the plasma membrane on the incubation with the cells at 4°C. When the cells were warmed to 37°C for various periods, HDL-HRP was internalized and delivered through coated vesicles and tubulo-vesicular system to endosomes at the periphery of cytoplasm. Further incubation revealed the distribution in endosomes of the Golgi region as well as trans-Golgi vesiceles, followed by resecretion out of the cells. Thus, these results disclosed the unique endocytosis -resecretion pathway of HDL in macrophages that we call HDL pathway. In addition, comparing the intracellular pathway of transferrin by the same approach, transferrin-HRP conjugates showed their indistinguishable movement through trans-Golgi vesicles from that of HDL.
Trans-Golgi system has recently been emphasized to play an important role in receptor recycling as well as membrane sorting (Pastan & Willingham). In the light of the present findings, we believe that HDL shares the same fate as transferrin through this compartment. Furthermore, it could be postulated that cholesterol transport from cholesterolloaded macrophages to HDL molecule might occur in this unique HDL pathway.

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The foam cell has been recognized as a characteristic feature of xanthomas and atheromas. Many foam cells in these lesions share properties characteristic of the macrophages. Therefore, the macrophage may be the progenitor of certain foam cells that are involved in atherogenesis. Several investigators demonstrated in vitro that macrophages can ingest large amounts of native lipoprotein, such as β-VLDL and WHHL-VLDL and also certain chemically modified lipoproteins, such as acetylated LDL and malondialdehyde-treated LDL through the process of receptor-mediated endocytosis and thereby they become foam cells. Yet modified LDL has not been demonstrated to exist in the body. Recently oxidized LDL is suggested to play an important role in atherogenesis by facilitating the accumulation of lipids in macrophages in vitro. Probucol, originally developed as an antioxidant, prevents this oxidative modification of LDL in vitro. Moreover, there are some clinical reports that probucol causes a regression of cutaneous and tendon xanthomas in homoyzgous FH patients.
Therefore we questioned whether in vivo probucol could prevent the progression of atherosclerosis in homozygous WHHL-rabbits, an animal model for familial hypercholesterolemia. Six months after treatment with probucol, the percentage of surface area of total thoracic aorta with visible plaques was 7.0±6.3%, whereas 54.2±18.8% in untreated WHHL-rabbits in spite of no reduction of plasma cholesterol level. LDL isolated from WHHL rabbits under treatment with probucol were shown to be highly resistant to oxidative modification by cupric ion and to be minimally recognized by macrophages. Thus, probucol could definitely prevent the progression of atherosclerosis in homozygous WHHL rabbits in vivo by limiting oxidative LDL modification and foam cell transformation of macrophages. Our study suggests the possibility that oxidized LDL is the true form of modified LDL that produces foam cells and atherosclerosis in vivo.

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To clarify the relationship between xanthoma cells and hyper or dyslipoproteinemia, we carried out a comparative study between changes in lipid value and PAG electrophoretograms of serum lipoproteins and ultrastructural changes of xanthoma cells with Clofibrate treatment. The electrophoretic patterns remained as type V, III, IIa of WHO classification, but the midband Lps pattern changed from CMLM to LM after the treatment.
In type V, III and broad midband lipoproteinemia, the xanthoma cells contained numerous electron translucent lipid vacuoles. The myelinated lipid vacuoles after treatment suggest that lysosomal processes actively occured in their cytoplasma. The xanthoma cells turned into some spindle, elongated or round shaped cells. The spindle shaped cells were smooth muscle cells and histiocytes, while the elongated cells or the round shaped cells were fibroblasts, lymphocytes or mast cells.
In some lesions of tendon xanthoma is type IIa, though the lipid droplets were deposited among the collagen fibrils, the xanthoma cells were not infiltrated. In other lesions, collagen fibrils appeared either irregularly fragmented or in homogenous matrix. The homogenized masses were composed of the infiltrated xanthoma cells, histiocytes and fibroblasts. LDLs may become the changed LDL, and the changed LDL may degenerate the collagen fibers and be phagocyted by macrophage.

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Intracellular accumulation of lipids occurs in macrophages and smooth muscle cells in atherosclotic vascular lesions and xanthomas associated with hypercholesterolemia. Blood monocytes are originally provided with receptors for native LDL, while macrophages are provided with another kind of receptors for denatured LDL named scavenger receptors. By treating the cells of a monocytic leukemia cell line, THP-1, by a phorbol ester, we could observe a rapid induction of the scavenger receptor with a decrease in LDL-receptor in a very short period of time (80% in 24hr). When we incubated the cells with acetylated LDL, the accumulation of cholesterol and other lipids took place and the cells were changed into foam cell. The cells can also synthesize and secrete apolipoprotein E. When we incubated the cells in the medium containing HDL or artificial lipid paricles containing apolipoprotein E, free cholesterol was released from the cell surface into the medium. The series of experiments provided us a convenient model for the study of development and regression of atherosclerosis. Probucol, a kind of antilipidemic drug provided with an activity as an antioxidant, prevented the lipid storage in macrophages. It inhibited the uptake of acetylated LDL and stimulated the release of cholesterol into the medium. Such in vitro observation explains why probucol is very effective in causing the regression of xanthomas and also in the prevention of atherosclerotic coronary heart diseases.

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Localization of intracellular ferritin in leukemic cells and normal leucocytes from 31 patients with leukemia has been studied by light and electron microscopic immunoperoxidase procedures. With light microscopic observation, positive immunostaining for ferritin was more frequently observed in leukemic cells under conditions of myelogenous and monocytic leukemia. It is noted that positive leukemic cells tended to increase in number in proportion as higher serum ferritin levels in myelogenous leukemia. On the other hand, a majority of leukemic cells and normal leucocytes in lymphatic leukemia exhibited weak or negative immunostaining for ferritin, even in cases with higher serum ferritin levels. With electron microscopic observation, intracellular ferritin which was detected as positive immunostaining with deposits of DAB molecules was diffusely distributed only in cytosol of any positive leukemic cells and normal leucocytes. There was no immunostaining for ferritin in nucleus, rough endoplasmic reticulum, Golgi complexes, mitochondria, and intracytoplasmic granules. Immature and blastic leukemic cells which contained intense positive immunostaining for ferritin were observed in acute myelogenous leukemia and blastic crisis of chronic myelogenous leukemia with considerably high levels of serum ferritin. These results suggested that myelogenous leukemic cells synthesized increased amounts of ferritin by free ribosomes and contributed to high levels of serum ferritin.

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A 59-year-old man was admitted because of fever and nasal obstruction. On admission, bilateral nasal cavities and the palate were replaced by necrotic tissue. Physical examination revealed cervical lymphadenopathy, hepatosplenomegaly and edema but no icterus. Nasal mucosa and cervical lymph node were biopsied and they showed diffuse proliferation of large tumor cells with convoluted nuclei admixing with macrophages. Tumor cells, studied immunohistochemically, were positive for Leu4, MT1, but negative for SmIg, B1, B2, MB1, OKM1, and the tumor was diagnosed as T-cell lymphoma.
During the course, pancytopenia rapidly progressed and the bone marrow aspiration showed hypoplastic marrow with increased large histiocytic cells but no apparent tumor cells. Clinical and laboratory features revealed disseminated intravascular coagulation (DIC). Chemotherapy with the CHOP regimen was initiated but he died of extensive hemorrhagic pneumonia and bronchopneumonia. Autopsy showed lymphoma cell infiltration in pharynx, tonsils, liver, spleen and lymph nodes of neck and carina. Activation of mature histiocytes with marked erythrophagocytosis was characteristic and seen throughout the mononuclear phagocytic system, i.e. splenic red pulp, hepatic sinusoids, lymph node sinuses and bone marrow.
This case would be clinically classified in so-called lethal midline granuloma, but histologically diagnosed as nasal T-cell lymphoma complicated by hemophagocytic syndrome and DIC. Erythrophagocytic histiocytosis was considered to be the reactive process to the opportunistic infection associated with the T-cell malignancy.

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In the present study, we investigated spontaneous amyloidosis occurred in white Pekin ducks to clarify the type of deposit fibrils and the mechanisms of fibril formation.
Amyloid protein of ducks was sensitive to oxidation with potassium permanganate and completely lost the affinity to Congo red. Immunohistochemically the proteins cross-reacted to the rabbit anti-human amyloid AA antibody. So it was concluded that amyloidsis of ducks was secondary type and the major component of amyloid was amyloid AA protein.
The precursor substance of AA protein of ducks was produced by hepatocytes, in similar fashion to human or rodents.
With regard to pathogenesis, ducks amyloidosis was influenced by preceding inflammation, because numerous cases of amyloid ducks showed various inflamed alterations in the sole of the foot zone.
In light- and electron microscopically, morphological deposition pattern of the fibrils showed a typical AA form. The fibrils were observed on the walls of blood vessels and the neighboring connective tissues. However, we could find a characteristic finding that amyloid fibrils were mainly formed in the cytoplasm of reticuloendothelial system cells, especially in the histiocytes. Subsequently, intracytoplasmic fibrils were transformed into a amyloid nodule and the nodules were also fused into a large homogeneous mass.

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Increasing attention has been payed to the development of lymphoma in patients with autoimmune diseases. However, reports of such cases are rare. Although familial aggregations of Adult T cell leukemia-lymphoma (ATLL) which have been frequently observed in Kyushu are pointed out, familial lymphomas other than ATLL are few in Japan.
We reported a case of extranodal lymphoma with transient monoclonal gammopathy via hypogammaglobulinemia occurred subsequent to idiopathic thrombocytopenic purpura after unsuccessive treatment of corticosteroids for 3 years. A 76 years old man developed left pleural effusion in November, 1985. Diagnosis of lymphoma (diffuse large cell, B cell type) was obtained by the examination of pleural biopsy specimens using immunohistochemical techniques. Chemotherapy was started. Chest X-P examined in March, 1986 revealed multiple nodules in the left lung and central nervous system involvement of lymphoma was documented in July, 1986. Patient died in October, 1986. Autopsy revealed neither lymph node swelling nor lymph node involvement of lymphoma.
His daughter who was 41 years old developed gastric pain in August, 1985. Biopsy specimen of gastric mass revealed lymphoma which was the same quality as father. In spite of gastrectomy and chemotherapy, she died in June, 1986

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