Effect of IL-15 addition on asbestos-induced suppression of human cytotoxic T lymphocyte induction

BACKGROUND@#Asbestos fibers possess tumorigenicity and are thought to cause mesothelioma. We have previously reported that exposure to asbestos fibers causes a reduction in antitumor immunity. Asbestos exposure in the mixed lymphocyte reaction (MLR) showed suppressed induction of cytotoxic T lymphocytes (CTLs), accompanied by a decrease in proliferation of CD8@*METHODS@#For MLR, human peripheral blood mononuclear cells (PBMCs) were cultured with irradiated allogenic PBMCs upon exposure to chrysotile B asbestos at 5 μg/ml for 7 days. After 2 days of culture, IL-15 was added at 1 ng/ml. After 7 days of MLR, PBMCs were collected and analyzed for phenotypic and functional markers of CD8@*RESULTS@#IL-15 addition partially reversed the decrease in CD3@*CONCLUSION@#These findings indicate that CTLs induced upon exposure to asbestos possess dysfunctional machinery that can be partly compensated by IL-15 supplementation, and that IL-15 is more effective in the recovery of proliferation and granzyme B levels from asbestos-induced suppression of CTL induction compared with IL-2.

The Comparison of Cytotoxic T-Lymphocyte Effects of Dendritic Cells Stimulated by the Folate Binding Protein Peptide Cultured with IL-15 and IL-2 in Solid Tumor

The current modalities for treating cancer employ not only single but multiple approaches involving surgery, radiotherapy and chemotherapy. Unfortunately, the survival outcome is not promising even with these approaches. Alternative approaches for cancer therapy are now emerging. Immunotherapy is aiming at both increasing the power, and in redirecting the specificity of the patients' immune system to attack the tumor cells. Recently, many studies using tumor associated lymphocytes (TAL) isolated from malignant ascites cultured in a media containing interleukin-2 exhibit antitumor responses. IL-2 is a lymphokine produced by T-cells. It facilitates activation, sustained growth and rescue from apoptosis. Lately, newly developed IL-15 has also exhibited antitumor activity similar to IL-2. IL-15 is a newly described cytokine produced from monocytes-marcrophages and T-cells. It has a different molecular structure but it functions like IL-2 by binding to the IL-2R beta and gamma c chain. These antitumor responses are mediated by the cytotoxic T lymphocytes (CTL) that recognize the antigen in the context of the MHC molecules using the T cell receptors. CD8+-CTL recognize the peptide epitopes that are processed from the cellular proteins in the context of the MHC class I molecules. These peptides have a restricted length of 8-11 amino acids. The folate binding protein (FBP) is overexpressed in over 90% of ovarian and 20-50% in breast cancers. The FBP is the source of the antigenic peptides that are recognized by a number of these CTL-TAL, and is antigenic to both ovarian and breast cancer in vivo. To define the antitumor response of IL-15 and its' FBP immunogenicity, a peptide defining epitope E39 and E75 were presented by the PMBC derived dendritic cells (DC) from healthy donors isolated by the CD14 method to ovarian and breast CTL-TAL. Stimulating both ovarian and breast CTL- TAL by E39 or E75 pulsed DC (DC-E39, DC-E75), in the presence of IL-15 and IL-2 can rapidly enhance or induce the E39 or E75 specific CTL activity. The antitumor activities were measured by a chromium release assay for the tumor specific lysis activity using the ovarian and breast cancer cell lines. The tumor specific lysis activity for the ovarian TALs for IL-15 vs IL-2 were 28.6+/-3.9% and 30.3+/-3.2%, respectively and in the breast TALs, they were 14.8+/-3.1% vs 13.5+/-2.9%, respectively. Using autologous tumor cells, a slightly higher tumor specific lysis activity was obtained for the ovarian TALs cultured in IL-15 compared to IL-2 (72.0+/-8.2% vs 68.5+/-3.6%). However, for the breast TALs, they were 39.5+/-4.2% vs 41.5+/-3.3%, respectively. IL-15 is a newly developed cytokine that shows promising antitumor activity similar to IL-2. However, it requires lower dosage and is less toxic. Therefore, IL-15 might be a potential anticancer immunotherapeutic agent.

Restoration of P-glycoprotein function is involved in the increase of natural killer activity with exogenous interleukin-15 in human immunodeficiency virus-infected individuals

A depressed level of natural killer (NK) activity is one of the various immunologic abnormalities in human immunodeficiency virus (HIV) infection. Interleukin-15 (IL-15), an immunotherapeutic candidate in HIV infection, increases NK activity and induces the excretion of CC-chemokines from divergent immune cells, but the mechanisms of NK activity enhancement by IL-15 stimulation is not clearly established in HIV infection. This study examined whether CC-chemokines, which are known to increase NK activity, are secreted adequately in HIV-infected individuals, and also investigated whether P-glycoprotein is involved in NK activity enhancement after IL-15 administration. NK activity increased with IL-15 stimulation in NK cells of HIV-infected individuals, as it does in normal NK cells. IL-15 stimulates NK cells to secrete CC-chemokines, such as, macrophage inflammatory protein-1alpha (MIP-1alpha), macrophage chemotactic protein-1alpha (MCP-1alpha) and regulated upon activation, normal T cells expressed and secreted (RANTES) in both HIV-infected individuals and controls with no significant difference. P-glycoprotein expression and function is decreased in HIV-infected individuals and restored only in NK cells of HIV-infected individuals after IL-15 stimulation. P-glycoprotein may play a role in the mechanism of increased NK cell activity in HIV-infected individuals after IL-15 stimulation.

Spontaneous programmed cell death of peripheral blood mononuclear cells from HIV-infected persons is decreased with interleukin-15

Interleukin 15 (IL-15) is an important regulatory cytokine in cellular immunity. In vitro replacement of IL-15 has been shown to enhance immunity in Human immunodeficiency virus type 1 (HIV-1) infected lymphocytes. We evaluated the effect of IL-15 on the survival of peripheral blood mononuclear cells of HIV patients by examining in vitro lymphocyte apoptosis, and correlated the process with Bcl-2 and Fas gene regulation. Peripheral blood mononuclear cells (PBMC) from 21 HIV-infected adults and 24 HIV-seronegative healthy individuals were isolated and cultured to determine the effect of escalating doses of IL-15 (0, 1, 10, 100, 1000 ng/mL) on apoptosis. Lymphocyte proliferation assay with (3H) TdR was measured and Bcl-2 and Fas gene regulation was observed. The results were as follows: 1) IL-15 reduced culture induced lymphocyte apoptosis in HIV patients in a dose dependent manner, and reached a plateau level at a concentration of 100 ng/ml; 2) IL-15 significantly reduced the level of apoptosis after 3 days (14%) and 5 days (15%) of culture in HIV patients, while no difference was observed in HIV (-) donors; 3) The percentage of viable cells among the total number of lymphocytes was significantly enhanced by 25% in HIV patients with IL-15; 4) Bcl-2 expression was decreased in HIV patients (53.9 +/- 12.3%) compared to HIV (-) donors (93.0 +/- 3.7%), and IL-15 increased Bcl-2 expression by 21.2 +/- 5.2% in HIV patients; 5) Fas expression was increased in HIV patients (70.2 +/- 4.6%) compared to HIV (-) donors (32.4 +/- 4.3%), and IL-15 increased Fas expression by 8.4 +/- 1.2% in HIV (-) donors. Our findings indicate that IL-15 may influence immunologic abnormalities in HIV infection, particularly its ability to prevent apoptosis of lymphocytes by suppressing the down-modulation of Bcl-2. This may provide an experimental basis for IL-15 immunotherapy.