Foxp3 expression in pancreatic carcinoma cells as a novel mechanism of immune evasion in cancer

The forkhead transcription factor Foxp3 is highly expressed in CD4+CD25+ regulatory T cells (Treg) and was recently identified as a key player in mediating their inhibitory functions. Here, we describe for the first time the expression and function of Foxp3 in pancreatic ductal adenocarcinoma cells and tumors. Foxp3 expression was induced by transforming growth factor-beta2 (TGF-beta2), but not TGF-beta1 stimulation in these cells, and was partially suppressed following antibody-mediated neutralization of TGF-beta2. The TGF-beta2 effect could be mimicked by ectopic expression of a constitutively active TGF-beta type I receptor/ALK5 mutant. Down-regulation of Foxp3 with small interfering RNA (siRNA) in pancreatic carcinoma cells resulted in the up-regulation of interleukin 6 (IL-6) and IL-8 expression, providing evidence for a negative transcriptional activity of Foxp3 also in these epithelial cells. Coculture of Foxp3-expressing tumor cells with naive T cells completely inhibited T-cell proliferation, but not activation, and this antiproliferative effect was partially abrogated following specific inhibition of Foxp3 expression. These findings indicate that pancreatic carcinoma cells share growth-suppressive effects with Treg and suggest that mimicking Treg function may represent a new mechanism of immune evasion in pancreatic cancer.

The WD repeat protein FAN regulates lysosome size independent from abnormal downregulation/membrane recruitment of protein kinase C

FAN (factor associated with neutral sphingomyelinase [N-SMase] activation) exhibits striking structural homologies to Lyst (lysosomal trafficking regulator), a BEACH protein whose inactivation causes formation of giant lysosomes/Chediak-Higashi syndrome. Here, we show that cells lacking FAN show a statistically significant increase in lysosome size (although less pronounced as Lyst), pointing to previously unrecognized functions of FAN in regulation of the lysosomal compartment. Since FAN regulates activation of N-SMase in complex with receptor for activated C-kinase (RACK)1, a scaffolding protein that recruits and stabilizes activated protein kinase C (PKC) isotypes at cellular membranes, and since an abnormal (calpain-mediated) downregulation/membrane recruitment of PKC has been linked to the defects observed in Lyst-deficient cells, we assessed whether PKC is also of relevance in FAN signaling. Our results demonstrate that activation of PKC is not required for regulation of N-SMase by FAN/RACK1. Conversely, activation of PKC and recruitment/stabilization by RACK1 occurs uniformly in the presence or absence of FAN (and equally, Lyst). Furthermore, regulation of lysosome size by FAN is not coupled to an abnormal downregulation/membrane recruitment of PKC by calpain. Identical results were obtained for Lyst, questioning the previously reported relevance of PKC for formation of giant lysosomes and in Chediak-Higashi syndrome. In summary, FAN mediates activation of N-SMase as well as regulation of lysosome size by signaling pathways that operate independent from activation/membrane recruitment of PKC.

Regulation of regulatory T cells: role of dendritic cells and toll-like receptors

Regulatory T cells (Treg) are characterized by high-level surface CD25 and intracellular FoxP3 expression. Treg are instrumental in the maintenance of peripheral immune tolerance and the control of adaptive immune responses. Naturally occuring Treg suppress T-cell responses by cell contact-dependent mechanisms, whereas induced regulatory cells, including Tr1 cells, secrete inhibitory cytokines such as transforming growth factor (TGF)-beta and interleukin-10. The interplay between Treg and antigen-responsive T cells is modulated by dendritic cells (DC). Whereas immature myeloid precursors of DC suppress T-cell activation per se and immature DC support Treg development, mature DC can override Treg-mediated suppression in vitro and in vivo. Mature DC activated through Toll-like receptor (TLR) pattern recognition receptors produce proinflammatory cytokines, including interleukin-6, which render responder T cells refractory to the suppressive effect of Treg. In addition, Treg also express certain TLR, and the activation and/or suppressor function of Treg is modulated directly by the respective ligands. In this review, we discuss current models of how signals delivered through innate immune receptors in response to pathogen-associated molecular patterns affect adaptive immune responses via modulation of Treg function.

Expression and function of Toll-like receptors in T lymphocytes

Toll-like receptors (TLRs) are widely expressed in the innate immune system. They recognize conserved microbial ligands such as bacterial lipopolysaccharide, lipopeptides or viral and bacterial RNA and DNA. TLRs play an essential role in innate immune responses and in the initiation of adaptive immune responses. However, certain TLRs are also expressed in T lymphocytes, and the respective ligands can directly modulate T cell function. TLR2, TLR3, TLR5 and TLR9 act as co-stimulatory receptors to enhance proliferation and/or cytokine production of T-cell receptor-stimulated T lymphocytes. In addition, TLR2, TLR5 and TLR8 modulate the suppressive activity of naturally occurring CD25(+)CD4(+) regulatory T cells. The direct responsiveness of T lymphocytes to TLR ligands offers new perspectives for the immunotherapeutic manipulation of T cell responses.

Perspectives of gammadelta T cells in tumor immunology

Subsets of human gammadelta T cells recognize tumor cell-expressed ligands that are not seen by the T-cell receptor of conventional alphabeta T cells. Vdelta1 T cells recognize MHC class I chain-related molecules A and B and UL-16-binding proteins expressed at variable levels on epithelial tumor cells and some leukemias and lymphomas. In addition, therapeutically used aminobisphosphonates and synthetic phosphoantigens activate Vdelta2 T cells, the dominant subset of gammadelta T cells in human peripheral blood that display strong cytotoxicity towards various epithelial tumors. Intentional activation of gammadelta T cells in vivo and/or adoptive cell therapy with in vitro expanded gammadelta T cells holds considerable promise as a novel immunotherapy in certain types of cancer.

Secretory lysosomes and their cargo in T and NK cells

Secretory lysosomes are specialized organelles that combine catabolic functions of conventional lysosomes with an inducible secretory potential. They are present in various hematopoietic cell types commonly characterized by the need for rapid mobilization and secretion of effector proteins. As an example, the cytotoxic effector function of T cells and natural killer cells strictly depends on the activation-dependent mobilization of such vesicles to the cytotoxic immunological synapse. This review focuses on some molecules that have been identified as cargo of secretory lysosomes and which play a major role in effector function of CTL and NK cells. We also briefly point to the fact that the dysregulation of formation and transport of secretory vesicles is causative for severe immunodeficiencies and autoimmunity observed in patients and also in mice that have been used as representative model systems to analyze the pathophysiological relevance of secretory vesicles in vivo.

An optimized method for the functional analysis of human regulatory T cells

Naturally occurring regulatory T cells (Treg) suppress the activation of antigen-responsive T cells in a cell contact-dependent manner. In order to investigate the impact of soluble mediators and receptor-ligand interactions on the interplay between naive T cells and Treg, a reproducible suppressor cell assay which functions in the absence of additional feeder cells or antigen-presenting cells is mandatory. Here, we describe such a method which is suited to study the modulation of responder T cell/Treg interactions in vitro. Treg were isolated from negatively purified total human CD4+ T cells by positive selection using anti-CD25 monoclonal antibody (MoAb)-coated Dynabeads followed by a detachment step. The remaining CD4+ CD25- responder T cells were cocultured with CD4+ CD25+ Treg in the presence of T-cell Activation/Expansion Beads from Miltenyi Biotec pre-coated with anti-CD3 plus anti-CD28 monoclonal antibody (MoAb). The optimal concentration for coating was 5 microg/ml for both MoAb. At this concentration, strong proliferation of responder T cells was elicited which was almost completely suppressed by Treg at 1:1 cell ratios. When higher concentrations of anti-CD3/anti-CD28 MoAb were used for coating, Treg also showed some degree of proliferation. The optimized suppressor assay proved to be highly reproducible and was used here to confirm the partial or complete reversal of Treg-mediated T-cell suppression by some cytokines (IL-2, IL-15), soluble IL-6 receptor/IL-6 fusion protein and recombinant GITR-ligand. Furthermore, our data confirm that Treg do not need other cell types to suppress proliferation of CD4+ CD25- responder T cells.

Inhibition of TNF receptor 1 internalization by adenovirus 14.7K as a novel immune escape mechanism

The adenoviral protein E3-14.7K (14.7K) is an inhibitor of TNF-induced apoptosis, but the molecular mechanism underlying this protective effect has not yet been explained exhaustively. TNF-mediated apoptosis is initiated by ligand-induced recruitment of TNF receptor-associated death domain (TRADD), Fas-associated death domain (FADD), and caspase-8 to the death domain of TNF receptor 1 (TNFR1), thereby establishing the death-inducing signaling complex (DISC). Here we report that adenovirus 14.7K protein inhibits ligand-induced TNFR1 internalization. Analysis of purified magnetically labeled TNFR1 complexes from murine and human cells stably transduced with 14.7K revealed that prevention of TNFR1 internalization resulted in inhibition of DISC formation. In contrast, 14.7K did not affect TNF-induced NF-kappaB activation via recruitment of receptor-interacting protein 1 (RIP-1) and TNF receptor-associated factor 2 (TRAF-2). Inhibition of endocytosis by 14.7K was effected by failure of coordinated temporal and spatial assembly of essential components of the endocytic machinery such as Rab5 and dynamin 2 at the site of the activated TNFR1. Furthermore, we found that the same TNF defense mechanisms were instrumental in protecting wild-type adenovirus-infected human cells expressing 14.7K. This study describes a new molecular mechanism implemented by a virus to escape immunosurveillance by selectively targeting TNFR1 endocytosis to prevent TNF-induced DISC formation.

Transfusion-Related Risks of Intradermal Allogeneic Lymphocyte Immunotherapy: Single Cases in a Large Cohort and Review of the Literature

PROBLEM

Lymphocyte immunotherapy (LIT) is applied in infertility treatment. Moreover, it has been suggested for prevention of rhesus D-hemolytic disease and as a vaccine for reduction of human immunodeficiency virus-1 susceptibility. Although transfusion-related problems have been rarely reported they were a matter of debate. Here we discuss extensive single-center experience with intradermal LIT for implantation failure and recurrent miscarriages.

METHOD OF STUDY

Retrospective 2- to 3-year follow-up of in vitro fertilization couples treated during 1996-2002 (feedback 2,848/3,041 = 93%), registering 930 deliveries. Prospective survey for acute reactions for 2000-2003 (feedback 2,687/3,246 = 83%). Review of the literature.

RESULTS

Infections of the patient and transplant rejection later in life are minor residual risks. Post-transfusion purpura was suspected once but not verified. Anaphylaxis or malignancy were not promoted. Fetal/newborn alloimmune disease (severe hemolytic disease, thrombocytopenia, neutropenia) were not observed.

CONCLUSION

Based on microbiological, immunological, and hematological testing the risks of intradermal LIT are low.

The murine TRAIL receptor signals caspase-independent cell death through ceramide

Death receptors such as the 55 kDa tumor necrosis factor (TNF) receptor (TNF-R55) or Fas can initiate both apoptotic (caspase-dependent) and caspase-independent routes to programmed cell death (PCD). Here, we demonstrate for the first time that the single murine receptor for (TNF)-related apoptosis-inducing ligand (mTRAIL-R2) can induce a caspase-independent form of PCD with necrosis-like features in addition to apoptosis. Analysis of morphological and cellular features of caspase-independent PCD in response to TRAIL and TNF suggests that mTRAIL-R2 and TNF-R55 elicit caspase-independent PCD through similar pathways, although without participation of cathepsins. Cells overexpressing acid ceramidase (AC), an enzyme that metabolizes the sphingolipid ceramide, show enhanced survival from TRAIL-induced caspase-independent PCD but not from apoptosis, implicating a function of ceramide as a key mediator in caspase-independent PCD (but not apoptosis) induced by mTRAIL-R2. In concert with the enhanced resistance of AC-overexpressing cells against caspase-independent PCD induced by TNF, our results suggest that ceramide acts as a common mediator of caspase-independent PCD caused by death receptors such as mTRAIL-R2 and TNF-R55.

Regulation of FasL expression: A SH3 domain containing protein family involved in the lysosomal association of FasL

As a death factor of T cells and Natural Killer (NK) cells, Fas Ligand (FasL) is stored in association with secretory lysosomes. Upon stimulation, these cytotoxic granules are transported to the cell membrane where FasL is exposed on the cell surface, shed or secreted. It has been noted before that the proline-rich domain within the cytosolic part of FasL is required for its vesicular association. However, the molecular interactions involved in targeting FasL to secretory lysosomes or to the plasma membrane have not been elucidated. We now identified a family of structurally related proteins that upon co-expression with FasL reallocate the death factor from a membrane to an intracellular localization. Members of this protein family are characterized by a similar domain structure and include FBP17, PACSIN1-3, CD2BP1, CIP4, Rho-GAP C1 and several hypothetical proteins. We show that all tested members of this "FCH/SH3-family" co-precipitate FasL from transfectants. The interactions strictly depend on functional SH3 domains within the FCH/SH3 proteins. Since co-expression of FasL with individual FCH/SH3 proteins dramatically alters the intracellular localization of FasL especially in non-hematopoietic cells, our data suggest that FCH/SH3 proteins might play an important role for the subcellular distribution and lysosomal association of FasL.

Identification of HLA-A*0201-presented T cell epitopes derived from the oncofetal antigen-immature laminin receptor protein in patients with hematological malignancies

The oncofetal Ag immature laminin receptor (OFA-iLR) is a potential target molecule for immunotherapeutic studies in several tumor entities, including hematological malignancies. In the present study, we characterize two HLA-A*0201-presented epitopes eliciting strong OFA-iLR peptide-specific human cytotoxic T cell (CTLs) responses in vitro. Both allogeneic HLA-A*0201-matched and autologous CTLs recognized and killed endogenously OFA-iLR-expressing tumor cell lines and primary malignant cells from patients with hemopoietic malignancies in an MHC-restricted fashion but spared nonmalignant hemopoietic cells. Spontaneous OFA-iLR peptide-specific T cell reactivity was detectable in a significant proportion of leukemia patients. Interestingly, in patients with chronic lymphocytic leukemia and multiple myeloma but not in those with acute myeloid leukemia, significant frequencies of OFA peptide-specific CTLs could be detected in an early stage of disease but disappeared in patients with progressive disease. The identification of OFA-iLR-derived peptide epitopes provides a basis for tumor immunological studies and therapeutic vaccination strategies in patients with OFA-iLR-expressing malignancies.

TCR trans-rearrangements: biological significance in antigen recognition vs the role as lymphoma biomarker

V(D)J rearrangements occur within loci of TCR and BCR genes, thus generating the diversity of the AgR repertoire. In addition, interlocus V(D)J rearrangements occur, giving rise to so-called "trans-rearrangements." Such trans-rearrangements increase the diversity of the immune receptor repertoire and can be expressed as functional chimeric TCR proteins on the surface of T cells. Although chimeric receptors are not pathogenic per se, the frequency of AgR trans-rearrangements correlates with the level of genetic instability and thus could be used as a predictive biomarker for lymphoma risk.

The adaptor protein Nck interacts with Fas ligand: Guiding the death factor to the cytotoxic immunological synapse

The Fas ligand (FasL) is a key death factor of cytotoxic T lymphocytes and natural killer cells. It is stored intracellularly as a transmembrane protein of secretory lysosomes. Upon activation, these vesicles are transported to the cytotoxic immunological synapse (IS), and FasL becomes exposed to the cell surface to trigger cell death through ligation of its receptor Fas (CD95) on the target cell. We propose that the FasL-associated adaptor protein Nck is involved in the actin-dependent transport of FasL-bearing secretory lysosomes to the IS. Nck binds to the proline-rich portion of FasL and alters its subcellular distribution when coexpressed in 293T cells. In T lymphocytes, endogenous Nck partially colocalizes with lysosome-associated FasL. When T cell clones or lines are exposed to target cells, both proteins and other components of secretory lysosomes (i.e., granzyme B or cathepsin D) are transported to the cell-cell interface. The present data suggest that T cell receptor engagement provokes a rapid, tyrosine kinase- and actin-dependent transport of Nck-associated FasL-carrying lysosomes to the contact area. Our observations support the previous notion that the unique cytoplasmic tail of FasL is crucial for its directed transport to the cell surface and into the assembling cytotoxic IS.

Direct costimulatory effect of TLR3 ligand poly(I:C) on human gamma delta T lymphocytes

TLR3 recognizes viral dsRNA and its synthetic mimetic polyinosinic-polycytidylic acid (poly(I:C)). TLR3 expression is commonly considered to be restricted to dendritic cells, NK cells, and fibroblasts. In this study we report that human gammadelta and alphabeta T lymphocytes also express TLR3, as shown by quantitative real-time PCR, flow cytometry, and confocal microscopy. Although T cells did not respond directly to poly(I:C), we observed a dramatic increase in IFN-gamma secretion and an up-regulation of CD69 when freshly isolated gammadelta T cells were stimulated via TCR in the presence of poly(I:C) without APC. IFN-gamma secretion was partially inhibited by anti-TLR3 Abs. In contrast, poly(I:C) did not costimulate IFN-gamma secretion by alphabeta T cells. These results indicate that TLR3 signaling is differentially regulated in TCR-stimulated gammadelta and alphabeta T cells, suggesting an early activation of gammadelta T cells in antiviral immunity.

Differential expression of CD126 and CD130 mediates different STAT-3 phosphorylation in CD4+CD25− and CD25high regulatory T cells

IL-6 is a pleiotropic cytokine involved in T-lymphocyte biology. Following IL-6 binding, the soluble IL-6R (CD126)-IL-6 complex can directly activate cells that express the signal-transducing gp130 (CD130) molecule, which mediates two distinct signals, mitogenesis by mitogen-activated protein kinase (MAPK) activation and anti-apoptosis by signal transducer and activator of transcription 3 (STAT-3) activation. This 'trans-signaling', also mediated by the soluble CD126/IL-6 fusion protein hyper-IL-6 (H-IL-6), contributes to the perpetuation of autoimmune diseases such as Morbus Crohn or rheumatoid arthritis. On the other hand, the homeostasis of cellular immune reactions and its failure leading to autoimmune diseases are critically controlled by regulatory T cells (Tregs). Here, we investigated the differential expression of CD126 and CD130 on subsets of human leukocytes in blood, tonsil and spleen. Among CD4+ T cells, differential expression of CD126 and CD130 was observed on the basis of CD25 expression. CD4+CD25- T cells were strongly CD126+ and CD130+, whereas CD25(high) Tregs expressed CD126 but little CD130. Both CD126 and CD130 were down-modulated on CD4+CD25- T cells following ligand binding, whereas only marginal modulation was observed on Tregs. Interestingly, we observed a correlation between CD126 and CD130 expression with STAT-3 phosphorylation in CD4+CD25- T cells compared with Tregs after stimulation with IL-6 or H-IL-6, whereas the MAPK extracellular signal-regulated kinase 1/2 were not activated by CD130 dimerization. The differential expression of CD126 and CD130 and subsequent STAT-3 phosphorylation might be relevant for the recently described role of IL-6 in the control of Treg activity.

The impact of electrical charge on the viability and physiology of dendritic cells

The use of electrical charge for electroporation or electrofusion is widely applied to customize dendritic cells (DC) and their immunological properties as anticancer vaccines. The aim of this study was to evaluate the influence of various electrical field strengths on the recovery, viability and physiology of DC. Immature DC were transferred into low-conductive medium and electrically charged within a range of 0-1500 V/cm. Viability was assessed by Trypan Blue dye exclusion or staining with impermeant nucleic acid stains and fluorescence-activated cell sorter analysis. Additionally, apoptosis was determined by flow cytometry after staining with Annexin-V, endocytosis by uptake of fluorescein isothiocyanate-dextran and metabolic activity by a standardized fluorescent live/dead assay. There was a strong correlation between the electrical field strength and the viability and physiology of DC. Field strengths > or =1000 V/cm significantly impaired viability, metabolism and endocytotic activity. Dual fluorescence with 7-7-amino-actinomycin D and Annexin-V demonstrated that loss of viability was predominantly due to necrosis rather than apoptosis. Field strengths < or =500 V/cm allowed to maintain good cell viability and recovery of DC and did not cause alterations of metabolism and endocytosis. Therefore, the frequently used amplification of field strengths to improve the efficacy of electroporation and electrofusion requires critical re-evaluation.

Activation of V gamma 9V delta 2 T cells by NKG2D

Human Vgamma9 Vdelta2 T cells recognize phosphorylated nonpeptide Ags (so called phosphoantigens), certain tumor cells, and cells treated with aminobisphosphonates. NKG2D, an activating receptor for NK cells, has been described as a potent costimulatory receptor in the Ag-specific activation of gammadelta and CD8 T cells. This study provides evidence that Vgamma9 Vdelta2 T cells may also be directly activated by NKG2D. Culture of PBMC with immobilized NKG2D-specific mAb or NKG2D ligand MHC class I related protein A (MICA) induces the up-regulation of CD69 and CD25 in NK and Vgamma9 Vdelta2 but not in CD8 T cells. Furthermore, NKG2D triggers the production of TNF-alpha but not of IFN-gamma, as well as the release of cytolytic granules by Vgamma9 Vdelta2 T cells. Purified Vgamma9 Vdelta2 T cells kill MICA-transfected RMA mouse cells but not control cells. Finally, DAP10, which mediates NKG2D signaling in human NK cells, was detected in resting and activated Vgamma9 Vdelta2 T cells. These remarkable similarities in NKG2D function in NK and Vgamma9 Vdelta2 T cells may open new perspectives for Vgamma9 Vdelta2 T cell-based immunotherapy, e.g., by Ag-independent killing of NKG2D ligand-expressing tumors.

Adverse effects of intradermal allogeneic lymphocyte immunotherapy: acute reactions and role of autoimmunity

BACKGROUND

Immunotherapy with allogeneic lymphocytes was introduced as a therapeutic option for selected infertile couples in different centres worldwide 20 years ago. It has been suggested for other indications as well, e.g. for pregnant women at risk of a child with Rhesus-D haemolytic disease, or as a vaccine which might reduce the receptiveness for HIV-1 infection. Here we report on our experience on adverse side-effects of intradermal lymphocyte immunotherapy (LIT) for infertile couples using partner's lymphocytes.

METHODS

Prospective 4 week follow-up of all couples from 2000 to 2003 for acute reactions (feedback 2687/3246 [corrected] 83%). All couples treated between 1996 and 2002 received questionnaires after 2-3 years (feedback 1914/3041, 63%).

RESULTS

Local reactions predominantly consisted of redness and itching for approximately 2 weeks. Systemic reactions could be attributed to LIT in 6-8%. Blisters at the injection sites were characteristic of LIT but not dependent on the HLA class I mismatch status between cell donor and host. The incidence of autoimmune disease was 0.1%. Four patients developed thromboembolism in pregnancy which was not ascribed to antiphospholipid syndrome.

CONCLUSIONS

Acute side-effects are comparable to those reported after intradermal vaccination for infectious diseases. Specific risks for anaphylaxis, autoimmune or graft versus host disease were not detected.