Search for the critical characteristics of phenotypically different B cell lines, Burkitt lymphoma cells and lymphoblastoid cell lines, which determine differences in their functional interaction with allogeneic lymphocytes

Recognition of B-CLL cells experimentally infected with EBV by autologous T lymphocytes

We compared 5-day-old cultures of two B-CLL clones experimentally infected with EBV for their interaction with autologous T lymphocytes. The clone which was strongly activated by the virus stimulated autologous T cells. It was also damaged by the cytotoxic T cells which were generated in mixed cultures with autologous lymphoblastoid cell lines (LCL). Cultured, non-infected CLL cells were not lysed by these effectors. The other B-CLL clone, which was activated to considerably lesser extent by the virus, did not stimulate the autologous T lymphocytes. While, also in this case cytotoxic function was generated in the mixed T cell-LCL culture, the effectors did not damage the EBV-infected CLL cells. The results with B-CLL cells can be regarded as a model for the EBV genome carrier normal B lymphocytes. They substantiate the current concept that such cells persist in seropositive healthy individuals undisturbed by the specific immune response as long as they maintain the phenotype of resting cells. However, after activation they can be recognized and eliminated by T cells.

In vitro culture of B-lymphocytes derived from Epstein-Barr-virus-associated posttransplant lymphoproliferative disease: cytokine production and effect of interferon-alpha

Epstein-Barr-virus-associated posttransplant lymphoproliferative disease ranges from transient lymphadenitis to aggressive lymphoma. This study characterizes an in vitro model to study the pathogenesis of this disease with a cell culture system. Five B-cell lines derived from posttransplant lymphoproliferative disease tissue were characterized with regard to immunophenotype, karyotype, molecular genetics, cytokine production, and growth regulation. All cell lines expressed CD19, CD21, CD22, CD43, and CD77, but not CD10 antigens. Immunoglobulin light chain restriction was seen in four of five cell lines, and cytogenetic abnormalities were demonstrable in three of the five. Cells proliferating in culture contained multiple Epstein-Barr virus episomes and showed lytic viral replication. All cell lines produced tumor necrosis factor-beta and interleukin-10 without evidence of autocrine growth regulatory loops involving these cytokines. No evidence of IL-1 alpha, IL-2, IL-4, IL-5 or IL-6 production was found by reverse transcriptase polymerase chain reaction. Adding 500 U IFN-alpha/ml to the culture medium resulted in 30% inhibition of [3H]thymidine incorporation.

Adhesion molecule CD11a/CD18-deficient Burkitt's lymphoma cells lack the transcript for the beta, but not the alpha, integrin subunit

Adhesion to cells and matrices participates in the regulation of lymphocyte proliferation, maturation and tissue localization. Consequently, abnormal patterns of adhesion molecule expression may contribute to the pathophysiology of lymphoproliferative disorders. Integrins are major cell-surface adhesive proteins composed by alpha and beta subunits. In contrast to normal lymphocytes, Burkitt's lymphoma (BL) cells lack the beta2 integrin CD11a/CD18. To study the molecular mechanism underlying this deficiency, presence of the transcript for each subunit was analysed by Northern blotting in group I BL lines (BL biopsy-like) and, for comparison, Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCLs). While transcripts for both CD11a (alpha subunit) and CD18 (beta subunit) were readily detected in LCLs, BL lines contained the transcript for the alpha subunit only. Treatment of BL cells with phorbol ester for 72 h induced expression of the beta subunit mRNA and the CD11a and CD18 antigens on the cell surface. The results indicate that the CD11a/CD18 deficiency of BL is due to absence of the beta subunit transcript and that this defect is restored by stimulation of the cells.

B-CLL cells experimentally infected with EBV enter DNA synthesis, produce cytokines and stimulate T-lymphocytes

Several B-chronic lymphocytic leukemia (B-CLL) clones, represented by different patients can be infected with EBV in vitro. A proportion of the cells becomes activated by the virus, but they rarely yield immortalized cell lines. We used cells from two B-CLL patients which differed in sensitivity to EBV infection. After 7 days in culture, we studied the CLL cells exposed to the B-cell activators Staphylococcus aureus, IL-2 and/or to EBV for expression of the activation markers CD23, CD39 and the adhesion and costimulatory molecules CD54 and CD80, for DNA synthesis, for production of various cytokines and for capacity to stimulate autologous and allogeneic T-lymphocytes. Generally the frequency of cells expressing cytokines in the cytoplasm correlated with the activation status of the populations and with their capacity to stimulate T-cells. It is likely that the difference between the clones with regard to sensitivity to the viral infection, is determined by the maturation state of the CLL cells. It may therefore reflect the variation in the response within a normal B-cell population. The results obtained in the present and in our earlier experiments with EBV provide information concerning the events after primary EBV infection in vivo. The T-lymphocyte stimulatory capacity of the infected CLL cells may be considered as an in vitro correlate to the syndrome of infectious mononucleosis. The detection of cytokines in the infected B-CLL cells suggests that their production by the B-blasts contributes to the level of T-lymphocytosis induced by the primary infection.

Characterization of B-cell lines from SLE patients and their relatives

Epstein-Barr-virus (EBV)-transformed lymphoblastoid B-cell lines were generated from peripheral blood lymphocytes of 55 patients with systemic lupus erythematosus (SLE) and 44 healthy relatives. All donors have previously been extensively characterized with regard to clinical, serologic, and genetic parameters. Here, peripheral blood lymphocytes and lines were characterized for cell surface antigens. Furthermore, autoantibody production and proliferation rate of the cell lines were monitored. A significant difference between patients and relatives was the lower proliferation rate of EBV-transformed cell lines of the SLE patients. All SLE cell lines are available for interested researches and can be obtained from the European Cell Bank, Salisbury, UK.

Novel tumor-associated accessory molecules involved in the gamma/delta cytotoxic T-lymphocyte-Burkitt's lymphoma interaction

BACKGROUND

Tumor specific cytotoxic T lymphocytes (CTL) recognize antigen via the T-cell receptor (TCR). In addition, recognition requires accessory molecules involved in adhesion and signal transduction. The authors previously have characterized an autologous, Burkitt's lymphoma specific CTL line that uses the gamma-delta TCR to recognize antigen in a nonclassical context. The current study was undertaken to identify novel accessory molecules involved in this unusual TCR-tumor cell interaction.

METHODS

A panel of monoclonal antibodies was generated against a Burkitt's lymphoma cell line and was screened for inhibition of autologous, tumor specific, cytolysis by a gamma-delta CTL line. Proteins identified by these monoclonal antibodies were further characterized by fluorescent-activated cell sorter analysis, Western blot and immunoprecipitation.

RESULTS

Three known (CD5, CD43, and CD11a/CD18) and three novel (BAM-1, BAM-2, and BAM-3) cell surface molecules involved in the gamma-delta CTL-Burkitt's lymphoma interaction were identified and characterized.

CONCLUSIONS

This study identifies and provides a preliminary characterization of three novel Burkitt's lymphoma-associated molecules involved in the gamma-delta CTL-tumor cell interaction and demonstrates that CD5, CD43, and CD11a/CD18 are involved in this interaction. It is likely that other unidentified accessory molecules are also involved in this and other effector cell-tumor interactions. Identification of such molecules may be useful in the design of new immunotherapeutic approaches.

EBV infection of B-CLL cells in vitro potentiates their allostimulatory capacity if accompanied by acquisition of the activated phenotype

Epstein-Barr virus (EBV)-carrying immortalized lymphoblastoid cell lines (LCLs) stimulate autologous T lymphocytes in vitro. This T-cell response is independent of the EBV-specific cellular memory because it also occurs in experiments with cells of seronegative individuals. The question can be posed whether the T-cell-stimulatory potential of the LCL is coupled to its immortalized state. B-CLL cells were exploited to study this question because the majority of clones, represented by different patients, can be infected with EBV but they rarely become immortalized. We have investigated the phenotypic changes and the T-cell-stimulatory capacity of EBV-infected B-CLL cells. One aliquot of CLL cells was infected with EBV, another was activated with a mixture of Staphylococcus aureus (SAC), IL-2 and the supernatant from the T-cell hybridoma MP6 (activation mixture, AcMx) and the third aliquot received both treatments. In accordance with the individual features of the clonal populations represented by each patient, the immunophenotypic changes imposed by these treatments differed. With the samples of 3 patients the allo-stimulatory potential showed the following ranking order: EBV and AcMx-treated cells > AcMx-treated > EBV-infected. An analysis of several activation-related surface markers and adhesion molecules on the cells did not reveal any association between their expression and the EBV-imposed potentiation of allostimulatory capacity. These results may be extrapolated to EBV-genome-carrying normal B cells, suggesting that they can persist in vivo only as long as they have the resting phenotype. Once they are activated, these cells may be recognized and eliminated by T lymphocytes.

Morphologic and immunophenotypic characterization of a cell line derived from liver tissue with Epstein-Barr virus associated post-transplant lymphoproliferative disease

A B-cell line was established from the liver of an 11-yr-old boy with Epstein-Barr virus (EBV)-associated post-transplant lymphoproliferative disease (PTLD). The cells were morphologically heterogenous, CD10 (CALLA) negative, and expressed several B-cell antigens, including CD23, in a manner reminiscent of lymphoblastoid cell lines (LCLs) reported in the literature. However, the cells also showed expression of the CD77 antigen, carried a 14q32+ chromosomal anomaly, and showed IgM-kappa immunoglobulin isotype restriction immediately after their outgrowth in culture. These latter properties are typically associated with Burkitt's lymphoma cell lines rather than LCLs. Aberrant expression of the L60 antigen on these B-cells was found as additional evidence of altered growth regulation in these cells. EBV infection was demonstrated by the abundant expression of EBNA-2 and LMP viral antigens in culture. The cell line described should be useful in planning in vitro experiments designed to understand the factors that modulate the growth of PTLD in vivo.

Action of natural killer cells and macrophages in cancer

According to the results obtained in several types of experiments the immunological anti-tumor effects that reflect the clinical situation involve T lymphocytes. The products of natural effector cells can contribute to anti-tumor immunity as part of the cytokine network. In addition, some cytokines can act on the tumor cells by influencing directly their proliferative capacity and/or through modification of their phenotype. In the tumor tissue the interaction between malignant cells and host cells on the one hand, and between the various types of host cells on the other hand, is complex. The participating mechanisms can act in both directions, with the result that the outcome of the balance may be either inhibition or stimulation of tumor growth.

Comparison of integrin adhesion molecules expressed by primary brain lymphomas and nodal lymphomas

The expression of 17 adhesion molecules was immunohistochemically examined in 5 primary cerebral lymphomas (PCL) and in 5 histologically similar nodal lymphomas (NL) to evaluate their possible involvement in selective targeting of lymphoma cells to the brain. PCL and NL tumor cells showed very similar expression patterns: they were consistently positive for alpha 3, alpha 4 and beta 1 integrin chains; negative for alpha 1, alpha 2, alpha 6, beta 3 and beta 4 integrin chains; and heterogeneous for alpha 5, alpha L, alpha M, alpha X, beta 2 and beta 7 integrin chains, as well as for intercellular adhesion molecule-1 (ICAM-1) and the selectin LECAM-1. Loosely infiltrating PCL showed lower levels of the alpha L beta 2 integrin than compact cell clusters. Vessels stained for ICAM-1 and vascular cell adhesion molecule-1 (VCAM-1). We conclude that the adhesion molecules implicated in the extravasation of non-neoplastic leukocytes (alpha 4 beta 1/VCAM-1 and alpha L beta 2/ICAM-1) are also expressed by both PCL and NL. The adhesion molecules examined are apparently not selective mediators of lymphoma cell homing to the brain, but at least alpha L beta 2 integrin might be related to the infiltration pattern of PCL within the brain parenchyma.