Effect of metabolic inhibitors on membrane immunofluorescence reactivity of established Burkitt lymphoma cell lines

Effect of radiation on the expression of carcinoembryonic antigen of human gastric adenocarcinoma cells

The changes of antigenic expression of cultured human gastric adenocarcinoma MKN45 cells caused by irradiation were investigated to elucidate the immune responses to localized irradiation. The expression of carcinoembryonic antigen (CEA) showed remarkable increases in the culture supernatant and on the surface of the membrane of irradiated cells. The expression of major histocompatibility complex Class I antigen on the membrane also was enhanced by irradiation. In addition, the irradiated cell groups, when analyzed using a CEA-specific probe, showed remarkable increases in the CEA mRNA. These enhancements increased in the 10-Gy and 15-Gy irradiated populations compared with the 5-Gy irradiated population. These results suggest that the enhancement of expression of CEA by radiation takes place at the CEA gene expression (mRNA) level but not at the protein level.

Detection by monoclonal antibodies of an early membrane protein induced by Epstein-Barr virus

Two monoclonal antibodies, E8B3 and E8D2, were raised against Epstein-Barr virus (EBV)-producing cells and were shown to immunoprecipitate a protein with an approximate molecular weight of 105,000 (p105). The protein was detectable only in EBV-containing cells which were supporting the virus lytic cycle, and its synthesis increased after cells were induced with phorbol esters. The molecule was radiolabeled and immunoprecipitated from virus-producing cells that had been extrinsically labeled with 125I, and the antibodies E8B3 and E8D2 reacted in immunofluorescence assays with infected cells; the molecule was also associated with virion particles. Synthesis of p105 was not blocked by phosphonoacetic acid and could be induced in Raji cells by superinfection with virus derived from P3HR1 cells. These data support the conclusion that p105 is an EBV-specific early membrane protein.

Differential induction of Epstein-Barr virus-related antigens in heterokaryon cultures

Different paterns of induction of Epstein-Barr virus (EBV)-related antigens were observed in heterokaryons produced by Sendai virus-mediated fusion of producer and non-producer human lymphoblastoid cells with various other cell types. EBV-related early antigens (EA) and viral capsid antigen (VCA) could obviously be induced in heterokaryons between producer cells (P3HR-1 and QIMR-WIL), normally expressing these natigens at very low frequency, and human FL or HeLa cells. Positive cells were detected as early as 3 h after fusion and there often followed a rapid increase in positive cells. In contrast, in heterokaryons between non-producer cells (Raji and NC-37) and FL or HeLa cells, only EA but not VCA was induced. EA induction was also evident in fusion of human lymphoblastoid cells with monkey cells (Vero) but with mouse cells (L-M(TK-) C11D and MCB-2) no EBV induction occurred. The EBV induction in heterokaryons was significantly enhanced by 5-iododeoxyuridine treatment.

Differential induction of Epstein-Barr virus-related antigens in human lymphoblastoid cells by virus-mediated cell-to-cell contact

Differential induction of Epstein-Barr virus (EBV)-related antigens was observed after Sendai virus-medicated fusion of producer and non-producer cells with various human and mouse cells. The EBV-determined early nuclear antigen (ENA), early antigen (EA) and viral capsid antigen (VCA) could be induced at a high rate in producer cells (P3HR-1 and B95-8), normally expressing these antigens at very low frequency, as early as 12-24 h after fusion with each other or with human amnion FL cells. In contrast, only one antigen, ENA, was induced in producer cells following fusion with non-producer cells. This limited induction occurred also in non-producer cells fused with FL cells, but not after fusion with each other. EBV induction did not result from fusion of either producer or non-producer cells with mouse cells (L-M (TK-) Cl1D and MCB-L). The differential induction was not the result of heterokaryon formation as determined by autoradiography. The implications of these findings are discussed.

Burkitt's lymphoma - a human tumor model system for immunological studies

Burkitt's lymphoma occurs mainly in parts of tropical Africa and has attracted the attention of experimental workers due to its epidemiological and clinical features, which indicate a viral etiology and a host immune response to the tumor. As a result of virological studies, Epstein-Barr virus (EBV) DNA has been demonstrated in almost all tested biopsies of African BL. This contrasts to the absence of EBV in all, or almost all, of the non-African Burkitt's lymphoma-like tumors, even though the number of tested tumors in this group is small, and to the lack of EBV in all other types of lymphoma or leukemia. Immunological studies have revealed the presence of antibodies to different EBV-associated antigens in all African patients with Burkitt's lymphoma. However the antibodies are not specific for Burkitt's lymphoma but are found in most adults all over the world, although at lower levels. They cannot therefore serve diagnostic purposes, but they can give prognostic information and occasionally give clues to the mechanisms behind late tumor recurrences, and possibly guide so-called immunotherapy. Burkitt's lymphoma patients contrast to appropriate control groups where some of the persons are anti-EBV seronegative, and this, together with the presence of EBV in Burkitt's lymphoma biopsies and the absence of EBV in other lymphomas, even though the cell type involved may be infectable by EBV in vitro and the tumor may arise in an EBV-carrying person, favors an etiological role in EBV in Burkitt's lymphoma and speaks against the "passenger" hypothesis, according to which EBV is picked up by the Burkitt's lymphoma cell which happens to be particularly suitable for EBV persistence. To explain the geographical distribution, a cofactor, such as certain forms of malaria, has been implied.

Human sarcomas in culture. Foci of altered cells and a common antigen; induction of foci and antigen in human fibroblast cultures by filtrates

In a study of human sarcomas maintained in culture for periods up to two years, the following observations were made. The most prominent cell type in serially cultured osteosarcomas was fibroblastic in appearance. After 16-20 wk in culture some lines spontaneously developed foci of altered cells resembling the foci produced in monolayer cultures by oncogenic viruses. The presence of these foci in the sarcoma cultures was transient, and usually they did not reappear; but in one instance they recurred with a characteristic periodicity of several weeks. From one of the sarcoma lines, in which foci appeared after 5 months in culture, two subcultures were established from stored frozen cells and these both exhibited foci after approximately the same lapse of time. The same phenomenon has been seen with another line, suggesting that the time of appearance of foci is characteristic for particular sarcomas. Foci of similar type could sometimes be induced in monolayer cultures of human fibroblasts by filtered medium from cultured sarcomas; this bore no relation to the presence or absence of foci in the sarcoma cultures at the time the filtrate was prepared. Electron microscopy of the spontaneous and induced foci, and of the sarcoma cultures, revealed no demonstrable virus. 12 out of 15 sarcoma cultures contained an antigen (S) demonstrable by indirect immunofluorescence with human sera. It was not present in any of the original sarcoma specimens, nor in any culture lines other than sarcomas. At least 3-4 wk in culture appear to be required for its demonstration. The antigen was cytoplasmic, occurred in only a small proportion of the cells, and was unpredictably variable in its expression, even in the same culture line. It could be induced in monolayer cultures of human fibroblasts by filtrates of medium from sarcoma cultures. As with the foci, the induction of S antigen in indicator cultures was not dependent upon the expression of antigen in the sarcoma line from which the filtrates were obtained. There was no association between the presence of foci and of antigen, nor was there any apparent relation between the ability of filtrates to induce foci and their ability to induce antigen. 80% or more of the general population have S antibody, and the titer of antibody in patients with sarcoma is no higher than in normal subjects. Thus, as in the case of Burkitt's lymphoma antigen, it appears that most individuals have been exposed to S antigen. But unlike Burkitt's lymphoma, no relation has so far been established between any particular disease and a corresponding high titer or frequency of occurrence of S antibody. The occurrence of foci of altered cells and of a common antigen, and the transmission of these two characters to indicator cells by filtrates, are all suggestive of a virus specifically associated with human sarcomas, one to which the general population is widely exposed, as indicated by the prevalence of antibody.