Relationships between susceptibility to LAK cell-mediated lysis, conjugate formation and expression of adhesion molecules in B-cell derived non-Hodgkin's lymphomas

Virus or TLR agonists induce TRAIL-mediated cytotoxic activity of plasmacytoid dendritic cells

Among dendritic cells, plasmacytoid dendritic cells (PDC) represent a functionally distinct lineage. Regarding innate immunity, PDC secrete large amounts of type I IFN upon viral exposure or stimulation by microbial products such as unmethylated CpG-motif containing oligo-DNA due to their selective expression of TLR7 and TLR9. We asked whether they could acquire cytotoxic functions during the early phases of infection or after activation with TLR7 or TLR9 agonists. In the present study, we describe a human PDC cell line called GEN2.2, derived from leukemic PDC, that shares most of the phenotypic and functional features of normal PDC. We show that after contact with the influenza virus, GEN2.2, as well as normal PDC, acquires TRAIL and killer activity against TRAIL-sensitive target cells. Moreover, we show that activation of GEN2.2 cells by CpG-motif containing oligo-DNA or R848 also induces TRAIL and endows them with the ability to kill melanoma cells. Therefore, PDC may represent a major component of innate immunity that could participate to the clearance of infected cells and tumor cells. This phenomenon could be relevant for the efficacy of TLR7 or TLR9 agonists in the therapy of infectious disease and cancer.

A defective expression of ICAM-1 (CD54) on secretory endometrial cells is associated with endometriosis

A defect in the cytolytic activity against autologous endometrial cells refluxed in the peritoneal cavity has been hypothesized as being involved in the etiology of endometriosis, although its causes have not been definitively identified. Cell adhesion molecules are necessary not only for cell-to-cell contact but also for the binding of immune effectors to their targets. In this study, the expression of CD54, CD58 and CD106, three adhesion molecules with a crucial role in cytotoxic mechanisms, was quantitatively studied on fresh endometrial cells by immunofluorescence and flow cytometry. Samples were collected from endometriosis patients (n=10) and controls (n=12), either during the follicular or luteal phase of the cycle. While no significant differences were observed for CD58 and CD106, a significantly reduced expression of CD54 in the secretory endometrial cells of women with endometriosis was observed (-75% with respect to apparently healthy controls). These findings could account for an apparently cyclic defect in the expression of CD54 that could result in poor binding of immune effectors to secretory endometrial cells in vivo. The defective recognition and removal of refluxed endometrial cells could, at least in part, be involved in the pathogenesis of endometriosis.

Cell mediated cytotoxicity assessment by relative changes in viable target absolute counts

We measured absolute counts (cells/microl) of Calcein-AM stained target cells that remained viable [i.e. not permeable to the viability probe 7-AAD (7-Amino Actinomycin D)] following a four-hour incubation with effectors [NK, CTL (cytotoxic T lymphocytes)] without using beads or standards. The absolute counts were evaluated by a Cytoron Absolute (Ortho) flow cytometry apparatus. Median triplicate counts were compared at 0 and 4h, in single targets and increased effector/target ratios. The Coefficient of Variation (CV) of the cell concentration (cells/microl) at the beginning of the experiment was below 6%. The % changes of viable target counts were correlated to the effector/target ratios by linear regression. The methodology was applied in pairs: 17 for allogenic stem cell transplantation from unrelated donors, 3 of healthy unrelated individuals, 10 for measuring NK activity and 7 autologous. In 15/20 allogenic MLC (mixed lymphocytes culture) and for all NK assays the cytotoxicity was positive (p < 0.05, r2 > 0.9) while in 5/20 allogeneic MLC and in all autologous MLC the outcome was negative (p > 0.05, r2 < 0.4). The proposed method offers the advantage of combining absolute counts with flow cytometry analysis of viable targets, assessment of cell behavior during the cytotoxic phenomenon, the use of a small amount of cells and excellent sensitivity. Our method can estimate frequencies higher than 1:100 for CTL assays.

Different Mechanisms of Resistance to Lymphokine-activated Killer (LAK) Cells in Leukemic Cell Sublines Selected by Etoposide or by LAK Cells

Two models of in vitro induction of human IM-9 lymphoblastoid cell line resistance to LAK cell-mediated killing were compared. IM-9 cell line variants were selected in vitro by prolonged exposure to LAK cells or to etoposide. Sensitivity to killing by LAK cells or by etoposide, conjugation with LAK cells and surface marker patterns were compared. Both LAK-cell-selected cell subline (IM-9/SL-15) and etoposide-selected cell subline (IM-9/ER) have acquired resistance to LAK cell-mediated death. IM-9/ER cells, but not IM-9/SL-15 cells, were 3.2-fold less sensitive to etoposide as compared to parental IM-9 cells. IM-9/SL-15 cells revealed decreased conjugation with LAK cells and augmented CDlla/CD18 surface molecule expression as compared to IM-9 line. In contrast, IM-9/ER cells displayed a level of conjugation with LAK cells equal to IM-9 cells, but loss of CD11a/C18 expression. Our results suggest different mechanisms of acquired resistance to LAK cells are operative in etoposide- or LAK-selected sublines, involving deterioration of LFA-1 molecule expression and altered conjugation properties, respectively.

From the study of tumor cell immunogenicity to the generation of antitumor cytotoxic cells in non-Hodgkin's lymphomas

The question of the immunogenicity of non-Hodgkin's lymphoma (NHL) B cells has been investigated in an attempt to support the development of new immunotherapeutic treatments for this disorder, which remains resistant to conventional treatments in most cases. In the present review, we report and discuss our new findings in the field of NHL B cell immunogenicity. One aspect of our work is the description of the expression and functions of membrane molecules associated with antigen presentation. The expression levels of adhesion molecules was measured, and the relevance of this expression to the sensitivity of malignant B cells to cell-mediated lysis was studied. Since the T cell response relies on the expression of both HLA class I and II molecules, we also investigated whether or not these molecules were present at the surface of NHL B cells. Subsequently, we asked whether antitumor CTL and LAK cells could be developed and analyzed the mechanisms of cell lysis involved. Since the generation of a T cell response requires the expression of the costimulatory molecules CD80 and CD86, we investigated their in vivo expression and their modulation in vitro during contact with responding T lymphocytes. The understanding of the immunogenicity of NHL B cells has enabled us to develop a new culture protocol to induce antitumor specific autologous CTL. The originality of NHL B cells--unlike most other tumor cells--is to be able to function as antigen presenting cells (APC) and to activate a T cell response in the absence of other professional APC. Over the next few years, these findings should allow the generation of anti-NHL specific T cells for adoptive immunotherapy and for the identification of NHL-associated antigens.

Differentiation of antitumor-specific cytotoxic T lymphocytes from autologous tumor infiltrating lymphocytes in non-Hodgkin's lymphomas

The present study describes a new culture protocol allowing the activation and proliferation of autologous tumor infiltrating T lymphocytes (TIL), and the generation of antitumor specific CTL in non-Hodgkin's lymphoma (NHL). Cells from eight patients with indolent NHL were used. We performed 3-week co-cultures of TIL with irradiated autologous malignant B cells in the presence of low doses of IL-1beta, IL-2 and IL-12. The proliferation, phenotype and cytotoxicity, and antitumor specificity of T cells recovered were studied. T-cell clonality was analyzed using TCRgamma gene rearrangement amplification by a multiplex PCR. Under these culture conditions, TIL proliferated, and the CD8+ T lymphocytes that were in a minority at the beginning of the culture increased dramatically in 6 out of 8 cases. In two cases, CD4+ T lymphocytes expanded. We showed that an oligoclonal selection of reactive T cells occurred in culture. Specific cytotoxicity developed against autologous malignant B cells in the 6 cases where there was an expansion of CD8+ T lymphocytes. Inhibition experiments performed with mAb directed against HLA class I and II molecules, CD4, CD8 and TCRgammadelta showed that the cytotoxic effector cells were CD8+ T lymphocytes probably expressing TCRalphabeta+. Cytokine secretion was analyzed in culture medium, and we detected significant levels of IFN-gamma, TNF-alpha, and IL-10 and no IL-4 (except in one case). Our results demonstrate that memory T cells from lymphoma patients can be amplified and differentiated into antitumor cytotoxic cells using a combination of the cytokines IL-1beta, IL-2, and IL-12 in association with non modified tumor cells.