Glycosidases from the interferon producing lymphoid cell line Namalva and from three other lymphoid cell lines

1. The occurrence of lysozyme, neuraminidase and fourteen other glycosidases was investigated in the three lymphoma cell lines Namalva, Raji and Daudi derived from a Burkitt's lymphoma and the lymphoblastoid cell line Robinson from Epstein-Barr virus transformed normal peripheral blood lymphocytes. High activity of beta-N-acetyl-D-glucosaminidase was found in three of the cell lines, which also showed fairly high activities of beta-N-acetyl-D-galactosaminidase, alpha-D-mannosidase and beta-D-mannosidase. In Daudi the highest glycosidase activity was found for beta-D-mannosidase. 2. Neuraminidase and lysozyme were not detected in any of the four cell lines. 3. These cell lines showed characteristic enzyme patterns and enzyme ratios which may be used for the identification of the cell lines. 4. When calculated on a protein basis no statistically significant change in glycosidase activities of the cells could be recorded during interferon production.     

In vitro sensitization of human lymphocytes against histiocytic lymphoma cell lines. I. Primary sensitization of lymphocyte subpopulations.

Peripheral blood lymphocytes from normal donors expressed spontaneous cytotoxic activity against human diffuse histiocytic lymphoma cell lines. In the unfractionated state, they could not be further sensitized in vitro against these cell lines. By applying cell separation techniques before culture, subpopulations of lymphocytes were obtained which could be sensitized in vitro and manifested cytotoxic activity against human histiocytic lymphoma cells. Three methods of separation were found effective: E rosette enrichment; elimination of Fc receptor positive cells; and removal of nylon wool adherent cells. Under these conditions, cross-reactive cytotoxicity was observed against non-neoplastic lymphoblastoid cell lines, but not against normal lymphocytes.     

Human leukemia-associated antigens: detection on cells of established lymphoblastoid lines.

Primate and rabbit antisera to different morphologic classes of human leukemia cells, after appropriate absorptions, detected leukemia-associated antigens present on cultured lymphoblastoid cell lines derived from leukemia patients. The primate antisera distinguished antigens on cells derived from myeloid leukemia patients from those on cells derived from lymphocytic leukemia patients. Of particular interest was the fact that antigens of myeloid leukemia, but not of lymphatic leukemia, were detected on lymphoid cell lines established from blood of patients with myeloid leukemia. One of four lymphoblastoid cell lines derived from normal donors expressed antigens of lymphatic leukemia. Leukemia-associated antigens were not found on the HRIK lymphoblastoid line derived from a Burkitt's lymphoma patient on skin fibroblasts or HeLa cells. Expression of these antigens on cultured cells derived from leukemia patients could not be related to the presence of the EB virus or the EB virus genome. Rabbit antisera detected antigens common to cells from patients with myeloid and lymphocytic leukemia. Absorption experiments demonstrated that the antigens detected on cell lines derived from leukemia patients are similar to those detected by the primate and rabbit antisera on fresh peripheral blood leukemic cells. The serologic detection of leukemia-associated antigens on lymphoblastoid cell lines indicates that some of these cultures contain cells with antigenic properties similar to those of human peripheral blood leukemic cells.     

Identification of the Epstein-Barr virus terminal protein gene products in latently infected lymphocytes.

The terminal protein (TP) gene produces two overlapping mRNAs in latently infected lymphocytes that are predicted to encode the similar polypeptides TP1 (497 amino acids) and TP2 (378 amino acids), with TP1 exon 1 providing 119 extra unique residues at the N terminus. Rabbit antisera were raised to procaryotic fusion proteins and used to detect expression of a predicted 53-kilodalton (kDa) TP product in transfected 293 cells and latently infected lymphocytes. Fractionation of transfected 293 cells showed this protein to be localized to an integral membrane preparation. The same fraction of latently infected lymphocytes contained proteins of 53 and 27 to 39 kDa as determined by Western immunoblotting with the TP-specific rabbit antisera. Immunoprecipitation of TP products from 35S-labeled human lymphoblastoid cells (CR/B95-8) was used in pulse-chase experiments and showed that TP1 was a labile protein with a half-life of approximately 2 to 4 h. The anti-fusion protein serum detected a 53-kDa TP1 and degradation products in the range of 25 to 35 kDa. A panel of Burkitt's lymphoma cell lines and cell lines established with virus recovered from the BL cells were analyzed by Western immunoblotting and found to contain the 53-kDa TP1 product, its degradation products, or both. Only two EBV-positive BL cell lines (BL72 and Wewak II) were negative in this assay. The results suggest that a labile TP1 protein may be expressed by most, if not all, EBV-infected cell lines.     

Restricted expression of EBV latent genes and T-lymphocyte-detected membrane antigen in Burkitt''s lymphoma cells.

Certain newly established Epstein-Barr virus-containing Burkitt's lymphoma cell lines do not express the cytotoxic T-lymphocyte-detected membrane antigen (LYDMA) through which EBV infection is normally controlled by the host. When the EB virus recovered from these BL lines was used to transform peripheral blood lymphocytes from seronegative donors, the lymphoblastoid cell lines (LCLs) that arose were all LYDMA positive. This indicates that the LYDMA-negative nature of the BLs is not the result of a mutation in the resident viral genome but is rather a specific adaptation in those cells, perhaps permitting evasion of the host immune surveillance in tumour development. A comparison of the EBV gene expression in six LYDMA-negative and two LYDMA-positive BL lines and in their corresponding LCLs revealed that several of the BL lines did not express all of the viral gene products classically associated with latent transformation by EBV. Four out of eight cell lines showed restricted expression of the latent membrane protein (LMP) and/or the EB nuclear antigen, EBNA 2. A new level of EBV gene regulation therefore appears to be operating in some of the BL cell lines. The patterns of expression of EBV genes in the cell lines did not show any correlation with the known susceptibility of the lines to T cell killing.     

Subpopulations of B cells in germinal centers. III. HJ6, a monoclonal antibody, binds globoside and a subpopulation of germinal center B cells.

To identify surface Ag uniquely expressed on human germinal center B cells, we produced a mouse mAb, HJ6. When tonsillar lymphocytes were examined, HJ6 did not label T cells and labeled only about half of PNA+ B cells that were HK23-. HJ6 did not label mononuclear cells from peripheral blood, splenocytes, and any of 29 cell lines including 23 B cell lines. This binding pattern of HJ6 was very similar to that of a mAb named 5B5. It was shown previously that 5B5 bound a glycolipid named CTH (CD77) and its Ag was expressed on HK23- PNA+ tonsillar lymphocytes and Burkitt's lymphoma cell lines. Despite the similarity, HJ6 differed from 5B5: HJ6 did not stain Burkitt's lymphoma cell lines and stained PNA+ tonsillar lymphocytes in the presence of a large concentration of galactose. When its binding to isolated glycolipids was studied, HJ6 was found to bind globoside and Forssman Ag and not to other glycolipids including CTH. When its binding to neutral glycolipids extracted from tonsillar lymphocytes was studied, HJ6 bound only globoside; Forssman Ag was not detected in tonsillar lymphocytes. Taken together, we conclude that globoside is a B cell Ag expressed on a subpopulation of germinal center B cells.     

Differential activation of cytotoxic responses by Burkitt's lymphoma (BL)-cell lines: relationship to the BL-cell surface phenotype

Epstein-Barr (EB) virus-positive Burkitt's lymphoma (BL) cell lines, recently established from tumour biopsies and displaying chromosomal translocations indicative of their malignant origin, can be classified into two broad sets: (i) lines growing predominantly as single cells/small clumps whose cell surface markers remain close to those of the original tumour cells, and (ii) lines whose growth pattern and cell surface markers have progressed closer to the more "lymphoblastoid" phenotype displayed by all in vitro transformed B-cell lines (LCLs) of normal origin. When compared to LCLs derived from normal B cells of the same patient, BL-cell lines in set (i) generally showed a lower expression of HLA class I and class II antigens and a reduced ability to activate both allospecific and nonspecific (natural killer-like) cytotoxic responses when cocultured with peripheral blood lymphocytes. By contrast, the HLA antigen expression and in vitro stimulatory capacity of most BL-cell lines in set (ii) were much closer to the values displayed by their corresponding LCLs. Since set (i) rather than set (ii) BL cell lines are phenotypically representative of the malignant cells as they exist in vivo, this work suggests that successful outgrowth of the virus-carrying tumour cells in the affected host may be facilitated by the inability of these cells to stimulate strong cytotoxic responses.     

Higher tyrosine protein kinase activity in resting lymphocytes than in proliferating normal or leukaemic blood cells

We have studied tyrosine phosphorylation in particulate fractions from 11 leukaemic cell lines by using as substrate either a synthetic tyrosine containing peptide or the endogenous proteins. The results were compared with those obtained using similar fractions from normal lymphocytes and bone marrow cells. Particulate fractions from all the leukaemic cell lines and normal bone marrow cells exhibited lower levels of tyrosine protein kinase activity compared to normal lymphocytes. When the phosphorylation of endogenous substrates was assayed, proteins were phosphorylated on tyrosine residues (rather than serine or threonine residues) to a larger extent in normal lymphocytes than in leukaemic cell lines. Separation of labelled endogenous substrates on sodium dodecyl sulfate-polyacrylamide gels showed a number of phosphorylated alkali-resistant bands in the range 14-175kd in the lymphoid cell lines; normal lymphocytes exhibited a smaller number of strongly phosphorylated bands. Normal lymphocytes from different individuals showed reproducible patterns of phosphorylated substrates. Normal bone marrow cells and myeloid leukaemia lines showed weak, if any, phosphorylation. Among the leukaemic cell lines no particular pattern of phosphorylated substrates common to cells of similar phenotype could be detected. We suggest that the level of overall tyrosine protein kinase activity in these fractions reflects their position in the cell cycle rather than their normal or malignant status.     

Effect of tumor necrosis factor alpha and infliximab on apoptosis of B lymphocytes infected or not with Epstein-Barr virus

Chronic inflammation and immunosuppressive therapies increase the risk of non-Hodgkin's lymphoma associated or not with Epstein-Barr virus (EBV) infection. A possible link between infliximab treatment and increased risk of lymphoma has been suggested. Indeed, infliximab induces apoptosis of monocytes and activated T lymphocytes, but its effect on B lymphocytes infected or not with EBV is unknown. Secreted tumor necrosis factor (TNF) alpha and the expression level of TNF receptor 1 (TNFR1) and TNFR2 were compared in EBV-positive and negative B-cell lines. The impact of TNFalpha and infliximab on apoptosis of EBV-positive cells was analyzed regarding the activity of NF-kappaB. Increased expression of TNFalpha in EBV-positive cells suggested that infliximab could affect their survival. However, TNFalpha or infliximab incubation had no effect on apoptosis of EBV-positive cells. Loss of NF-kappaB activity sensitized lymphoblastoid cell lines to TNFalpha-induced apoptosis, but no direct effect of infliximab on apoptosis was detected. On the basis of our in vitro data, neither TNFalpha nor infliximab has a direct effect on apoptosis of B lymphocytes and EBV-positive cell lines. Thus, if an increased incidence of lymphoma were induced by TNFalpha blockers, it would not involve a direct effect on B cells but rather an impaired immune surveillance by T cells.     

B lymphoblastoid cell lines with rearranged T cell receptor beta-chain genes retain conventional B cell surface antigen and Ig expression

Transformation of peripheral blood lymphocytes by co-incubation with EBV produces B lymphoblastoid cell lines, but rearrangement of TCR beta-chain genes was observed in three different cell lines derived from two individuals. Because rearrangement of TCR genes in B lymphocytes is considered a rare event, these B lymphoblastoid cell lines with rearranged TCR beta-genes were examined in detail to determine whether there were any additional characteristics to distinguish them from B lymphoblastoid cell lines with germ-line TCR beta-genes. All B lymphoblastoid cell lines contained rearranged Ig H and kappa L chain genes, secreted Ig, and expressed B and not T cell surface markers. Cell lines with rearranged TCR beta-genes had rearranged both IgH genes and had rearranged and subsequently deleted both kappa C region genes. Furthermore all three B lymphoblastoid cell lines with rearranged TCR beta-genes produced small amounts of Ig with lambda-L chains. Although the cellular mechanisms maintaining lineage-specific rearrangement events remain unknown, extensive Ig gene rearrangement and inefficient Ig production by B cells may be indicators of a cellular status where normally stringent lineage-specific control elements fail to function efficiently.     

Influence of ataxia telangiectasia gene dosage on bleomycin-induced chromosome breakage and inhibition of replication in human lymphoblastoid cell lines

Long-term lymphoblastoid cell lines, obtained by E-B virus transformation of peripheral blood lymphocytes, retain many of the features of hypersensitivity to environmental agents found in primary cultures and fibroblast strains from patients with genetic diseases. Primary lymphocyte cultures from patients with ataxia telangiectasia, a cancer-prone genetic disease, have increased sensitivity to chromosomal damage induced by the radio-mimetic drug, bleomycin. In order to study the expression of ataxia telangiectasia gene dosage in lymphoblastoid cell lines, we examined chromosomal aberrations in lines containing two, one, or no alleles for ataxia telangiectasia. These were derived from ataxia telangiectasia homozygotes, from ataxia telangiectasia obligate heterozygotes, and from presumably normal donors, respectively. Chromosome preparations were made 46 h after a 2 h exposure to bleomycin and scored for chromosome breakage, for the relative rate of cell replication as assessed by sister chromatid differentiation patterns, and for the frequency of sister chromatid exchanges. Baseline frequencies of chromosome breakage and sister chromatid exchanges, and baseline rates of cell replication were similar in all nine lymphoblastoid cell lines. Following treatment with 25 or 250 mU/ml bleomycin, all the lymphoblastoid cell lines showed increased chromosome breakage and decreased cell replication. The lymphoblastoid cell lines from the ataxia telangiectasia homozygotes had significantly increased chromosome breakage and decreased rate of cell replication after either bleomycin dose in comparison with the normal or with the ataxia telangiectasia heterozygous lines. Sister chromatid exchange frequencies were not altered by bleomycin exposure.     

Lymphocytes stimulated by allogeneic B cell lines cleave the third component of complement and fix C3 fragments. Their nonspecific lytic capacity is elevated against complement receptor type 2-carrying targets

Human blood lymphocytes stimulated in mixed cultures by allogeneic B cell lines were shown to cleave C3 molecules. The B cell lines were derived from Burkitt lymphoma patients: 1) established from their EBV-negative lymphoma, 2) the EBV-positive sublines converted in vitro, and 3) lymphoblastoid cell lines (LCL) i.e., B lymphocytes transformed in vitro by EBV. These cell lines differed considerably in their capacity to stimulate allogeneic lymphocytes. The split products of C3 were detected in the supernatants and on the surface of the activated lymphocytes at levels which correlated with the strength of stimulation. Lymphocytes cultured with LCL had the highest levels of thymidine incorporation blast transformation, C3 cleavage, and C3 fragment fixation. Lymphocytes exposed to the EBV-negative Burkitt lymphomas were stimulated weakly and their C3-activating capacity was low. Irrespective of the efficiency of lymphocyte stimulation induced in the cultures, 60 to 70% of the blasts were found to fix C3 fragments. The majority of the lymphocytes which fixed C3 fragments were T blasts that carried the CD3 marker and expressed IL-2R (CD25). CD4 and CD8 cells were represented with equal frequency in the C3-fragment fixing and C3-fragment negative populations. Pre-exposure of the MLC-activated lymphocytes to human serum increased their cytotoxic capacity toward CR type 2-carrying targets. The enhanced lysis was abrogated by F(ab)2 rabbit anti-human C3d or rabbit anti-CR type 2 antibodies. The results suggest that the C3 fragments fixed on the lymphocytes bind to CR on the targets and elevate the avidity of binding between the two interacting cells. This was also indicated by an increase in the frequency of lymphocyte-target conjugates.     

In vitro growth of B lymphocytes infiltrating human melanoma tissue by transformation with EBV: evidence for secretion of anti-melanoma antibodies by some transformed cells

Epstein Barr virus was used to transform the B lymphocytes infiltrating metastatic tumor tissue from seven patients with melanoma. In this way it was possible to establish continuously growing B lymphoblastoid cell lines (LCL) derived from the tumor-infiltrating B lymphocytes from each of the seven patients. Antibody production of up to 50 micrograms/ml could be achieved by such cultures, and the lymphoblastoid cells could be cloned readily by limit dilution on a feeder layer of irradiated fetal fibroblasts. Preliminary analysis of the antibodies produced by lymphoblastoid cell lines established from tumors from two of the patients indicated that most were of IgM type and bound to a panel of melanoma cell target cells, as well as to some nonmelanoma tumor cell lines. Cloned LCL were produced from the tumor-infiltrating B cells from one of the patients, and of 100 such clones tested, 9% secreted antibody that bound to autologous tumor cells, and one of these clones produced antibody that appeared to be melanoma specific.     

Cap formation on lymphocytes from patients with leukemic diseases induced by four different lectins.

When ficoll purified peripheral blood lymphocytes were treated with fluorescein conjugated lectins from lentils (LCH), castor beans (RCA) and phaseolus coccineus beans (L-and E-PHA) for 15 min and the percentages of the cap forming cells were examined, the values of leukemic lymphocytes were reduced compared to the values obtained with normal lymphocytes. The reduction was more than half in patients with acute and chronic myelogenous leukemia and immunoblastoma, it was only one quarter in patients with chronic lymphocytic leukemia, Hodgkin's disease and lymphosarcoma. The lowest number of cap forming cells was found in lymphoblasts of established lymphoblastoid cell lines. The four different lectins showed nearly the same capacity in the induction of caps. After successive binding, the different lectins showed cocapping on the lymphocyte surface.     

Sister chromatid exchange in cell lines from malignant lymphomas (lymphoma lines)

Summary The frequency of sister chromatid exchanges (SCEs) was studied in cells from three freshly established lymphoma lines, derived from two patients with Hodgkin's disease and one patient with non-Hodgkin lymphoma. These values were compared to SCE rates found in cells from two long-established lymphoma lines (Raji and BJAB) and to those recorded in control cell lines of normal human donors. The highest SCE levels were demonstrated in the freshly established lymphoma lines, the lowest SCE values separated the lymphoblastoid cell lines from healthy controls, and the older lymphoma lines Raji and BJAB presented rates in between. The influences of BUDR concentration and of the duration of BUDR treatment on the frequency of SCEs were tested. Furthermore, the dependence of the SCE rate on the time interval between establishment of the cell line and its SCE investigation was considered. The connection between elevated SCE rates and the neoplastic nature of lymphoma lines is discussed.     

Human B lymphocytes activated by Epstein-Barr virus (EBV) or by mitogens suppress mitogen-induced immunoglobulin production

Polyclonal activation of human B lymphocytes by LPS or protein A, alone or in combination or by Epstein-Barr virus (EBV), generates suppressive conditions that inhibit the response of human B lymphocytes to pokeweed mitogen (PWM), measured by the induction of immunoglobulin-secreting cells (PFC). Moreover, EBV-transformed B cell lines of normal or neoplastic (Burkitt lymphoma) origin also suppressed the PWM-induced immunoglobulin production of normal B cells. Cell separation experiments have shown that mitogen activated autologous B cells stimulate suppressor T cells in a similar way as B cell-derived lymphoblastoid cell lines. The significance of this phenomenon is considered in relation to the escape of the activating microorganism or virus from immune control and the occurrence of network interactions within the immune system.     

Specific sites for EBV association in the Namalwa Burkitt lymphoma cell line and in a lymphoblastoid line transformed in vitro with EBV

Localization of Epstein-Barr virus (EBV) DNA was studied by in situ hybridization on chromosomes from the Namalwa Burkitt lymphoma cell line and from a lymphoblastoid cell line transformed in vitro (ATL9/g). The five chromosome bands 1p32, 1q31, 5q21, 13q21, and 16p13 showed the presence of EBV DNA in both of the lines. Grain deposition at the site on chromosome 1q of the Burkitt line was particularly intense. It was also found that EBV DNA in the lymphoblastoid cell line co-localized with a stable achromatic gap at 1p32 whose presence seems to confer a proliferative advantage on the cells.     

Interferon production potentials of various human lymphoblastoid cell lines

A number of human lymphoblastoid cells were examined concerning their ability to produce spontaneously liberated and virus-induced interferon (IFN). It was found that, in addition to B cells, various T and nonT-nonB lymphoblastoid cells responded well to Sendai virus infection to form IFN, the characterization of which has been recently reported (20). One B lymphoblastoid cell line from an infectious mononucleosis (IM) patient produced a large amount of IFN-alpha and might become an alternative source of IFN production. Among 68 cell lines examined, 35 cell lines liberated 10 U/ml or more of IFN spontaneously in culture fluid. The presence of Epstein-Barr virus (EBV) genome or its activation appears to have no correlation with the spontaneous liberation of IFN. Spontaneously produced IFN from three cell lines was characterized as IFN-alpha. Comparatively higher amounts of IFN were produced in cells from IM patients than those from Burkitt's lymphoma cases or healthy adults. Spontaneously produced IFN was detected more easily in cells transformed by EBV alone than in those transformed by EBV and a tumor promoter, TPA.     

Immunofluorescent study of non-histone protein-DNA complexes in cultured cells and lymphocytes

Antibody against non-histone chromosomal protein-DNA complex of C-6 cells derived from human lymphoblastoid cells were prepared. By immunofluorescent studies using the antibody, nuclear fluorescence, which was speckled or clumped in appearance, was observed in cultured human lymphoblastoid cell lines, cultured human epithelial cell lines and human peripheral lymphocytes. In the human peripheral lymphocytes, there was a distinct variation in intensity of the nuclear fluorescence among the cell population. On the contrary, no nuclear fluorescence was observed in cultured animal cell lines.