Effect of interleukin-15 on effector and regulatory function of anti-CD3/anti-CD28-stimulated CD4(+) T cells

Azithromycin modulates immune response of human monocyte-derived dendritic cells and CD4+ T cells

Azithromycin (AZM) is a macrolide antibiotic that exhibits anti-inflammatory activity aside from its antimicrobial effect, a feature that may ameliorate certain inflammatory disorders and prevent graft-versus-host disease in patients receiving stem cell transplantation. In the present study, we investigated the ability of AZM to influence the function of human monocyte-derived dendritic cells (DCs) and CD4⁺ T cells. We found that AZM down-regulated CD80, CD86, and HLA-DR expression in lipopolysaccharide (LPS)-stimulated DCs and suppressed interleukin (IL)-6, IL-10, IL-12, and tumor necrosis factor-alpha production in these cells. In addition, AZM increased endocytosis and/or expression of Toll-like receptor (TLR)2, TLR4, and TLR9 in DCs and suppressed anti-CD3/CD28-induced CD4⁺ T cell proliferation and interferon-gamma production, an effect that was synergistic with dexamethasone. Finally, AZM suppressed DC-induced allogeneic T cell proliferation and cytokine production. Our study demonstrates that AZM modulates DC and CD4⁺ T cell function and may be of therapeutic benefit in various inflammatory disorders.

Interleukin-15 enhances the expansion and function of natural killer T cells from adult peripheral and umbilical cord blood

Invariant natural killer T cells (iNKT cells) are innate-like non-conventional T cells restricted by the CD1d molecule that are unique in their ability to play a pivotal role in immune regulation. Deficient iNKT function has been reported in patients receiving umbilical cord blood (UCB) transplantation. We sought to determine the effect of interleukin (IL)-15 on α-galactosylceramide (α-GalCer)-expanded iNKT cell function from UCB and adult peripheral blood (APB) mononuclear cells (MNCs). Fresh APB and UCB MNCs were cultured with IL-15 (50 ng/ml) in the presence or absence of α-GalCer (100 ng/ml) for 10 days. Cells were harvested for examination of cell yield, apoptosis, cytokine production and cytotoxic function of Vα24(+)/Vβ11(+) iNKT cells. We observed that α-GalCer-expanded APB and UCB iNKT cells and such expansion was further enhanced with IL-15. The percentage of CD3(+)CD56(+) NKT-like cells in both APB and UCB MNCs was increased with IL-15 but not with α-GalCer. Apoptosis of UCB iNKT cells was ameliorated by IL-15. Although APB and UCB iNKT cells secreted lower IFN-γ, it could be enhanced with IL-15. The expression of perforin in APB iNKT cells can also be enhanced with IL-15. UCB Vα24(+)Vβ11(+) iNKT cells further augmented K562 cytotoxicity mediated by IL-15. Taken together, these results demonstrated the relative functional deficiencies of α-GalCer induced UCB iNKT cells, which can be ameliorated by IL-15. Our findings suggest a therapeutic benefit of IL-15 immunotherapy during the post-UCB transplant period when iNKT function remains poor.

Interleukin‑15: a potent adjuvant enhancing the efficacy of an autologous whole‑cell tumor vaccine against Lewis lung carcinoma

Lung cancer is a major cause of cancer‑associated mortality worldwide due to its limited response rate to current chemotherapy and radiation, thus immunotherapy is rapidly becoming the most promising approach. Although the highly specific tumor‑associated antigen of lung cancer has been found, autologous whole‑cell tumor vaccines remain indispensable in the development of therapeutic cancer vaccines. Interleukin (IL)‑15 is a T helper type 1 cytokine that has been demonstrated to have a marked antitumor immune response and the potential ability to reverse the host tolerance of tumor antigens in certain preclinical trials. In the present study, a cationic liposome encapsulating IL‑15 gene‑loaded plasmid acted as an adjuvant of an autologous whole‑cell tumor vaccine by subcutaneous injection. The combination immunotherapy resulted in significant inhibition of tumor growth without side effects in the preventive tumor inhibition and adoptive therapy study. Cytotoxic lymphocyte assay detection of the serum antigen and cytokines using an enzyme‑linked immunosorbent assay suggested that the IL‑15 gene can significantly improve the cellular immune response and humoral immune response provoked by autologous whole‑cell tumor vaccines. These results demonstrated that the IL‑15 gene was an effective adjuvant of autologous whole‑cell tumor vaccines against mouse lung cancer and may provide an attractive vaccine strategy for cancer immunotherapy.

Generation of tumor-specific T lymphocytes using dendritic cell/tumor fusions and anti-CD3/CD28

Adoptive immunotherapy with tumor-specific T cells represents a promising treatment strategy for patients with malignancy. However, the efficacy of T-cell therapy has been limited by the ability to expand tumor-reactive cells with an activated phenotype that effectively target malignant cells. We have developed an anticancer vaccine in which patient-derived tumor cells are fused with autologous dendritic cells (DCs), such that a wide array of tumor antigens are presented in the context of DC-mediated costimulation. In this study, we demonstrate that DC/tumor fusions induce T cells that react with tumor and are dramatically expanded by subsequent ligation of the CD3/CD28 costimulatory complex. These T cells exhibit a predominantly activated phenotype as manifested by an increase in the percentage of cells expressing CD69 and interferon gamma. In addition, the T cells upregulate granzyme B expression and are highly effective in lysing autologous tumor targets. Targeting of tumor-specific antigen was demonstrated by the expansion of T cells with specificity for the MUC1 tetramer. Stimulation with anti-CD3/CD28 followed by DC/tumor fusions or either agent alone failed to result in a similar expansion of tumor-reactive T cells. Consistent with these findings, spectratyping analysis demonstrates selective expansion of T-cell clones as manifested by considerable skewing of the Vbeta repertoire following sequential stimulation with DC/tumor fusions and anti-CD3/CD28. Gene expression analysis was notable for the upregulation of inflammatory pathways. These findings indicate that stimulation with DC/tumor fusions provides a unique platform for subsequent expansion with anti-CD3/CD28 in adoptive T-cell therapy of cancer.

The regulatory function of umbilical cord blood CD4(+) CD25(+) T cells stimulated with anti-CD3/anti-CD28 and exogenous interleukin (IL)-2 or IL-15

The abundance of CD4(+) CD25(+) regulatory T cells in umbilical cord blood (UCB) might contribute to the decreased severity of graft-vs.-host disease (GVHD) for UCB transplantation. This study aims to characterize the phenotypes and suppressive function of UCB CD4(+) CD25(+) T cells under the influence of anti-CD3/anti-CD28 (CD3/CD28) and exogenous interleukin (IL)-2 or IL-15. Higher percentages of CD4(+) CD25(high) and FoxP3(+) cells were detected in UCB compared to their adult counterparts. IL-15 was as effective as IL-2 in enhancing the proliferation of CD3/CD28 stimulated UCB CD4(+) CD25(+) T cells. Phenotypically, IL-2/IL-15-stimulated UCB CD4(+) CD25(+) T cells expressed higher level of CTLA-4, GITR, membrane bound transforming growth factor-beta (mTGF-beta), and especially Foxp-3 than controls. IL-2/IL-15-stimulated UCB CD4(+) CD25(+) T cells also produced much higher IL-10 and TGF-beta than controls; while IL-2/IL-15-stimulated UCB CD4(+) CD25(-) T cells showed increased TGF-beta, but not IL-10 production. IL-2/IL-15-cultured UCB CD4(+) CD25(+) T cells showed comparable suppressor activity on allogeneic adult CD4(+) T-cell proliferation compared to controls, partly through a contact-dependent fashion. Taken together, IL-2/IL-15-stimulated UCB CD4(+) CD25(+) T cells show distinct regulatory T-cell phenotypic and functional features, and may be applied for the alleviation of GVHD severity following UCB transplantation.

Alloreactivity of ex vivo-expanded T cells is correlated with expansion and CD4/CD8 ratio

Background We have demonstrated previously that retroviral-mediated transfer of a suicide gene into bone marrow (BM) donor T cells allows an efficient control of graft-versus-host disease (GvHD) after allogeneic BM transplantation. However, the 12 days of ex vivo culture required for the production of gene-modified cells (GMC), including soluble CD3 monoclonal antibody (MAb)-mediated activation and expansion with interleukin (IL)-2, induced a decrease of GMC alloreactivity and a reversal of their CD4/CD8 ratio. Improving the culture protocol in order to maintain the highest alloreactivity is of critical importance in obtaining an optimal graft-versus-leukemia (GvL) effect. Methods Peripheral blood mononuclear cells were activated with soluble CD3 MAb or CD3 and CD28 MAb co-immobilized on beads and expanded for 12 days in the presence of IL-2, IL-7 or IL-15 before analysis of alloreactivity and phenotype. Results Replacing the CD3 MAb by CD3/CD28 beads led to similar in vitro alloreactivity but improved the expansion and in vivo alloreactivity of GMC. Replacing the IL-2 with IL-7, but not IL-15, or decreasing IL-2 or IL-7 concentrations, improved the in vitro alloreactivity of expanded cells but was associated with lower expansion. Indeed, the alloreactivity of expanded cells was negatively correlated with cell expansion and positively correlated with CD4/CD8 ratio and CD8 expression level. Discussion Quantitative (i.e. low CD4/CD8 ratio) and qualitative (e.g. low CD8 expression) defects may account for the decreased alloreactivity of GMC. Using CD3/CD28 beads and/or IL-7 is more beneficial than CD3 MAb and IL-2 for preventing perturbations of the alloreactivity and phenotype of GMC.

Hematopoietic Growth Factors Including Keratinocyte Growth Factor in Allogeneic and Autologous Stem Cell Transplantation

The aim of hematopoietic stem cell transplantation (HSCT) is to cure patients of malignancies, autoimmune diseases, and immunodeficiency disorders by redirecting the immune system: the often described graft-versus-leukemia (GVL) or graft-versus-tumor (GVT) effects. Unfortunately, fulfillment of this goal is often hampered by relapse of the underlying disease, graft-versus-host disease (GVHD), or severe opportunistic infections, which account for the majority of post-transplantation deaths. Moreover, studies of long-term survivors of transplantation indicate an accelerated immune aging due to the transplantation procedure itself, preceding chemo- or radiotherapy, and acute and chronic GVHD. Significant advances have been made towards overcoming these obstacles by enhancing immune reconstitution with hematopoietic growth factors (HGFs) such as granulocyte colony-stimulating factor (G-CSF) or erythropoietin (EPO) or through the application of cytokines. In addition, there are approaches to promote the thymic-dependent development of naive T cells, which are prepared for the interaction with a multitude of pathogens. Examples are the application of keratinocyte growth factor (KGF), neuroendocrine hormones such as growth hormone or prolactin, sex hormone ablation, or the invention of a three-dimensional artificial thymus based on a cytomatrix. Might these measures result in a higher rate of healthy and fully recovered patients? Here we review progress in each of these areas.

Differential cyclosporin-A sensitivity on survival and activation of umbilical cord and adult peripheral blood CD4+ T cells

Enhanced cyclosporine-A (CsA) sensitivity of umbilical cord blood (CB) CD4(+) T cells may contribute to the lower incidence of graft-versus-host disease (GVHD) after mismatched CB transplantation. Interleukin (IL)-15, an IL-2 like gamma-chain signaling cytokine, may bypass CsA inhibition and play an important role in GVHD pathogenesis. The present study examines CsA sensitivity of IL-15-driven CB CD4(+) T cell survival, activation and proliferation, comparing adult peripheral blood (APB) CD4(+) T cell responses. We establish that (1) resting CB CD4(+) T cells were more susceptible to CsA-induced cell death than their adult counterpart; (2) IL-15 help support the survival of resting CB CD4(+) T cell under the influence of CsA, though to a lesser degree that observed in adults; (3) higher CsA sensitivity of CD25 up-regulation following TCR activation was observed in CB but more readily counteracted by IL-15 compared to adults; (4) IL-15-driven proliferation of TCR-activated CD4(+) T cells was more susceptible to CsA inhibition than corresponding adults; and (5) TCR-activated CB CD4(+) T cells surviving high dose CsA (5 microg/ml) in IL-15-supplemented cultures expressed significantly lower percentages of CD45RO(-)/CD25(+) subsets compared to corresponding APB. Taken together, the differential CsA sensitivity and IL-15 response between CB and APB CD4(+) T cells may contribute to the lessened GVHD severity in the setting of CB transplantation.

TCR-independent cytokine stimulation induces non-MHC-restricted T cell activity and is negatively regulated by HLA class I

Recent evidence suggests that the functional status of T cells activated independently from their TCR differs substantially from classical MHC-restricted T cells. Here, we show that TCR-independent, short-term stimulation via the common gamma-chain of the IL-2/IL-15 receptor induces non-MHC-restricted cytotoxicity and sustained cytokine secretion in purified CD4+ or CD8+ T cells. NK-like cytotoxicity is directed against MHC class I-negative targets and can be inhibited by classical and non-classical HLA class I molecules. Known inhibitory receptors, such as CD85j (ILT2) and leukocyte-associated Ig-like receptor-1, are not responsible for this HLA-mediated inhibition. NK-like cytotoxicity can be costimulated by NKG2D (CD314) triggering, but 2B4 (CD244) and DNAM-1 (CD226) are not involved. NK-like T cells display an activated phenotype and secrete various cytokines, including IFN-gamma, TNF-alpha, IL-5, IL-13 and MIP-1beta. Under normal conditions, HLA class I-mediated inhibition may function as a safety mechanism to prevent unbalanced cytokine production and effector killing mechanisms by T cells that were activated independently from their TCR. Non-MHC-restricted activity represents a functional status rather than a property of distinct T cell subpopulations. Thus, cytokine-induced, non-MHC-restricted T cells may be relevant in immune responses against tumors showing aberrant MHC expression through their capacities of cytokine production and direct tumor cell eradication.