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A transfusion-transmitted hepatitis E case by blood from a donor infected via the zoonotic food-borne route and the progress of HEV markers in the entire course are demonstrated. Further studies are needed to clarify the epidemiology and the transfusion-related risks for HEV even in industrialized countries.

The clinically observed HBV infection risk caused by blood components from occult HBV carriers with low anti-HBc titers who slip through the JRC screening system is more than 10-fold lower than the transmission risk by donations in the pre-HBsAg and/or MP-NAT window phase.

The patient was infected with HEV via transfused blood from a volunteer donor. A potential risk of posttransfusion hepatitis E should be considered even in nonendemic countries.

Eighteen mouse monoclonal antibodies were selected for reactivity with cell surface antigens of the immunizing human melanoma cell line SK-MEL-28. Six distinct antigenic systems were defined by direct serological assays and absorption tests with a panel of 41 cell lines derived from normal and malignant human tissues. Biochemical analysis indicated that two of the antigens are glycoproteins with molecular sizes of 95,000 and 150,000 daltons (gp95 and gplS0). Two other antigenic systems (05 and the R24 group) are associated with heat-stable molecules having the characteristics of glycolipids.The remaining two antigens (M19 and R%) are heat labile, but molecular characterization has not been possible. Each of the antigenic systems has a distinctive pattern of distribution on various cell types, varying from a broad representation to a more restricted occurrence. Os appears to be a species antigen, being present on virtually every human cell type tested. gp95, gplS0, M19, and R8 are found on a characteristic proportion of melanomas, astrocytomas, and epithelial cancers and on normal kidney cells. The antigen defined by the R24 antibody has the most restricted distribution of all. Reactivity is found with melanomas and astrocytomas, whereas epithelial cell types, fibroblasts, and cells of hematopoietic origin lack R24. Although occurrence of gp95, gpl50, M19, and B8 distinguishes a small subset of melanomas not expressing these antigens, R24 is found on all melanoma cells. Cloning of Hybridomas and Passage in Mice. After cell colonies 1-2 mm in diameter formed, samples of supernatants were harvested and assayed for antibody by using PA-MHA tests against an initial screening panel of 10 human cell lines-5 melanoma cell lines (SK-MEL-13, -27, -28, -31, -37) and 5 nonmelanoma cell lines (SK-RC-6 and -7, ME-180, EBV-B cells, and sldn fibroblasts). Cells from wells containing antibody were passaged at low cell density (two to five cells per well) and, if antibody continued to be detected, the cells were cloned (one cell per well) two consecutive times. Cultures of cloned hybridomas were injected subcutaneously into nu/nu mice (Swiss background) and also were stored in liquid nitrogen. Sera from mice with progressively growing tumors were collected, stored at either -20'C or -70'C, and used for serological and biochemical analysis. Sera were obtained from mice prior to tumor inoculation, and only mice with low levels of preexisting natural antibody against human cells were used.Immunoprecipitation Procedures. SK-MEL-28 cells were labeled as follows: (i) surface labeling with 125I by the lactoperoxidase procedure (4), (ii) metabolic incorporation of[a5S]methionine (Amersham, 1000 Ci/mmol; 1 Ci = 3.7 X 101" becquerels) by using 250 MCi in 10 ml of methionine-free minimal essential medium containing 1% fetal bovine serum for 16 The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely...

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We recently reported that thymocytes from 6-month-old preleukemic AKR mice express higher levels of murine leukemia virus (MuLV)related antigens than thymocytes from 2-month-old mice. We have now found that the level of xenotropic MuLV (defined operationally as MuLV able'to infect mink cell cultures) is also-markedly increased in thymus of 6-month-old AKR mice and that-this increase in virus correlates closely with increased MuLV-antigen expression. There is no increase of MuLV antigen or xenotropic virus in spleen or lymph nodes. Production of ecotropic MuLV remains unchanged with age in thymus, lymph nodes, and spleen. Thymic grafts from 6-month-old AKR mice, but not from 2-month-old mice, induce both amplified MuLV-antigen expression and xenotropic virus production in the thymus of young AKR recipients. Experiments with lethally irradiated AKR mice reconstituted with syngeneic bone marrow cells indicate that age-related changes in the thymus rather than in bone marrow precursor cells are responsible for MuLV-antigen amplification.The critical role of the thymus in murine leukemogenesis is well known (1). In many strains of mice with a high incidence of spontaneous leukemia, the thymus is the first site of recognizable disease, and thymectomy early in life prevents its development (2). The great majority of such leukemias have T-cell markers (3), indicating that these cells have undergone some phase of their differentiation in the thymic environment. The etiology of mouse leukemia is complex, with murine leukemia virus (MuLV) (4, 5), genetic factors that limit or facilitate virus or leukemia cell replication and spread (5, 6), and humoral factors presumably elaborated by thymic stromal cells (1, 7) each playing a role.Before the onset of leukemia, characteristic changes occur in the thymus of mice from the high-leukemia AKR strain: (a) the thymic cortex is reduced in size, and structures resembling lymphoid follicles and germinal centers may appear in the medulla (1); (b) the level of adenylate cyclase in the thymus increases (8); and (c) the thymocyte undergoes a marked change in the expression of certain cell surface antigens (9, 10). We have reported recently that starting at about 4-5 months, MuLVrelated antigens (GIx, GCSA, p3O, and gp7O) and H-2 alloantigens on thymocytes show a progressive increase, whereas the differentiation alloantigen Thy-i is reduced (9).The present study is a further analysis of the preleukemic changes occurring in AKR mice, with the following questions Abbreviations: MuLV, murine leukemia virus; anti-NTD, (W/Fu X BN)F1 anti-W/Fu leukemia (C58NT)D antiserum. t Present address: