Immune tolerance induction by integrating innate and adaptive immune regulators

Recruitment of CCR6+ Foxp3+ regulatory gastric infiltrating lymphocytes in Helicobacter pylori gastritis

Helicobacter pylori (H. pylori) infection is associated with an inflammatory response in the gastric mucosa, leading to chronic gastritis, peptic ulcers, and gastric cancer. Increased T-cell infiltration is found at sites of H. pylori infection. The CCR6⁺ subset of CD4⁺ regulatory T cells (Tregs), a newly characterized subset of Tregs, has been reported to contribute to local immune inhibition. However, whether CCR6⁺ Tregs are present in H. pylori gastritis, and what their relationship is to disease prognosis, remains to be elucidated. In this study, gastric infiltrating lymphocytes were isolated from endoscopic biopsy specimens of H. pylori gastritis patients and analyzed. We found that in gastric infiltrating lymphocytes, CCR6⁺  CD4⁺  CD25^high Tregs, which express high levels of CD45RO, are positively associated with more severe inflammation in gastric mucosa during H. pylori infection. Furthermore, the frequency of CCR6⁺ Tregs in gastric infiltrating lymphocytes, but not CCR6^- Tregs, is significantly increased in inflamed gastric tissues, which is inversely correlated with significantly lower expression of IFN-γ⁺  CD8⁺ T cells. We also found that the frequency of CCR6⁺ Tregs is positively correlated with the frequency of CD4⁺  IFN-γ⁺ T cells. In addition, the frequency of CCR6⁺ Tregs, but not that of CCR6^- Tregs, is significantly correlated with increased inflammation in H. pylori gastritis. This study demonstrates that immunosuppression in H. pylori gastritis might be related to the activity of CCR6⁺ Tregs, which could influence disease prognosis.

Extracellular ATP signaling and clinical relevance

Since purinergic signaling was discovered in the early 1970s, it has been shown that extracellular nucleotides, and their derivative nucleosides, are released in a regulated or unregulated manner by cells in various challenging settings and then bind defined purinergic receptors to activate intricate signaling networks. Extracellular ATP plays a role based on different P2 receptor subtypes expressed on specific cell types. Sequential hydrolysis of extracellular ATP catalyzed by ectonucleotidases (e.g. CD39, CD73) is the main pathway for the generation of adenosine, which in turn activates P1 receptors. Many studies have demonstrated that extracellular ATP signaling functions as an important dynamic regulatory pathway to coordinate appropriate immune responses in various pathological processes, including intracellular infection, host-tumor interaction, pro-inflammation vascular injury, and transplant immunity. ATP receptors and CD39 also participate in related clinical settings. Here, we review the latest research in to the development of promising clinical treatment strategies.

Immunometabolic Phenotype Alterations Associated with the Induction of Disease Tolerance and Persistent Asymptomatic Infection of Salmonella in the Chicken Intestine

The adaptation of Salmonella enterica to the eukaryotic host is a key process that enables the bacterium to survive in a hostile environment. Salmonella have evolved an intimate relationship with its host that extends to their cellular and molecular levels. Colonization, invasion, and replication of the bacteria in an appropriate host suggest that modification of host functions is central to pathogenesis. Intuitively, this subversion of the cell must be a complex process, since hosts are not inherently programmed to provide an environment conducive to pathogens. Hosts have evolved countermeasures to pathogen invasion, establishment, and replication through two types of defenses: resistance and tolerance. Resistance functions to control pathogen invasion and reduce or eliminate the invading pathogen. Research has primarily concentrated on resistance mechanisms that are mediated by the immune system. On the other hand, tolerance is mediated by different mechanisms that limit the damage caused by a pathogen’s growth without affecting or reducing pathogen numbers or loads. The mechanisms of tolerance appear to be separated into those that protect host tissues from the virulence factors of a pathogen and those that limit or reduce the damage caused by the host immune and inflammatory responses to the pathogen. Some pathogens, such as Salmonella, have evolved the capacity to survive the initial robust immune response and persist. The persistent phase of a Salmonella infection in the avian host usually involves a complex balance of protective immunity and immunopathology. Salmonella is able to stay in the avian ceca for months without triggering clinical signs. Chronic colonization of the intestinal tract is an important aspect of persistent Salmonella infection because it results in a silent propagation of bacteria in poultry stocks due to the impossibility to isolate contaminated animals. Data from our lab promote the hypothesis that Salmonella have evolved a unique survival strategy in poultry that minimizes host defenses (disease resistance) during the initial infection and then exploits and/or induces a dramatic immunometabolic reprogramming in the cecum that alters the host defense to disease tolerance. Unfortunately, this disease tolerance results in the ongoing human food safety dilemma.

Colonic Insult Impairs Lymph Flow, Increases Cellular Content of the Lymph, Alters Local Lymphatic Microenvironment, and Leads to Sustained Inflammation in the Rat Ileum

BACKGROUND

Lymphatic dysfunction has been linked to inflammation since the 1930s. Lymphatic function in the gut and mesentery is grossly underexplored in models of inflammatory bowel disease despite the use of lymphatic occlusion in early models of inflammatory bowel disease. Activation of the innate and adaptive immune system is a hallmark of TNBS-induced inflammation and is linked to disruption of the intrinsic lymph pump. Recent identification of crosstalk between lymphatic vessel resident immune cells and regulation of lymphatic vessel contractility underscore the importance of the timing of lymphatic dysfunction during tissue inflammation in response to TNBS.

METHODS

To evaluate lymphatic function in TNBS induced inflammation, lymph was collected and flow measured from mesenteric lymphatics. Cellularity and cytokine profile of the lymph was also measured. Histopathology was performed to determine severity of injury and immunofluorescent staining of the mesentery was done to evaluate changes in the population of immune cells that reside near and on gastro-intestinal collecting lymphatics.

RESULTS

Lymph transport fell 24 hours after TNBS administration and began recovering at 72 hours. Significant reduction of lymph flow preceded significant increase in histopathological score and occurred simultaneously with increased myeloperoxidase activity. These changes were preceded by increased MHCII cells surrounding mesenteric lymphatics leading to an altered lymphatic environment that would favor dysfunction.

CONCLUSIONS

Alterations in environmental factors that effect lymphatic function occur before the development of gross GI inflammation. Reduced lymphatic function in TNBS-mediated inflammation is likely an early factor in the development of injury and that recovery of function is associated with resolution of inflammation.

Immunosuppression in early postnatal days induces persistent and allergen-specific immune tolerance to asthma in adult mice

Bronchial asthma is a chronic airway inflammatory condition with high morbidity, and effective treatments for asthma are limited. Allergen-specific immunotherapy can only induce peripheral immune tolerance and is not sustainable. Exploring new therapeutic strategies is of great clinical importance. Recombinant adenovirus (rAdV) was used as a vector to make cells expressing cytotoxic T lymphocyte-associated antigen-4-immunoglobulin (CTLA4Ig) a soluble CTLA4 immunoglobulin fusion protein. Dendritic cells (DCs) were modified using the rAdVs together with allergens. Then these modified DCs were transplanted to mice before allergen sensitization. The persistence and specificity of immune tolerance were evaluated in mice challenged with asthma allergens at 3 and 7 months. DCs modified by CTLA4Ig showed increased IL-10 secretion, decreased IL-12 secretion, and T cell stimulation in vitro. Mice treated with these DCs in the early neonatal period developed tolerance against the allergens that were used to induce asthma in the adult stage. Asthma symptoms, lung damage, airway reactivity, and inflammatory response all improved. Humoral immunity indices showed that this therapeutic strategy strongly suppressed mice immune responses and was maintained for as long as 7 months. Furthermore, allergen cross-sensitization and challenge experiments demonstrated that this immune tolerance was allergen-specific. Treatment with CTLA4Ig modified DCs in the early neonatal period, inducing persistent and allergen-specific immune tolerance to asthma in adult mice. Our results suggest that it may be possible to develop a vaccine for asthma.

Myeloid derived suppressor and dendritic cell subsets are related to clinical outcome in prostate cancer patients treated with prostate GVAX and ipilimumab

Background

Cancer-related disturbances in myeloid lineage development, marked by high levels of myeloid-derived suppressor cells (MDSC) and impaired dendritic cell (DC) development, are associated with poor clinical outcome due to immune escape and therapy resistance. Redressing this balance may therefore be of clinical benefit. Here we investigated the effects of combined Prostate GVAX/ipilimumab immunotherapy on myeloid subsets in peripheral blood of castration-resistant prostate cancer (CRPC) patients as well as the putative predictive value of baseline and on-treatment myeloid parameters on clinical outcome.

Methods

Patients with CRPC (n = 28) received thirteen intradermal administrations of Prostate GVAX, consisting of two allogeneic GM-CSF-transduced and irradiated prostate cancer cell lines (LN-CaP and PC3) and six infusions of escalating doses of anti-CTLA4/ipilimumab. Frequencies and activation status of peripheral blood DC (PBDC) and MDSC were determined before, during and after treatment by flowcytometric analysis and related to clinical benefit.

Results

Significant treatment-induced activation of conventional and plasmacytoid DC subsets (cDC and pDC) was observed, which in the case of BDCA1/CD1c⁺ cDC1 and MDC8⁺/6-sulfoLacNAc⁺ inflammatory cDC3 was associated with significantly prolonged overall survival (OS), but also with the development of autoimmune-related adverse events. High pre-treatment levels of CD14⁺HLA-DR⁻monocytic MDSC (mMDSC) were associated with reduced OS. Unsupervised clustering of these myeloid biomarkers revealed particular survival advantage in a group of patients with high treatment-induced PBDC activation and low pretreatment frequencies of suppressive mMDSC in conjunction with our previously identified lymphoid biomarker of high pretreatment CD4⁺CTLA4⁺ T cell frequencies.

Conclusions

Our data demonstrate that DC and MDSC subsets are affected by prostate GVAX/ipilimumab therapy and that myeloid profiling may contribute to the identification of patients with possible clinical benefit of Prostate GVAX/ipilimumab treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-014-0031-3) contains supplementary material, which is available to authorized users.

Autoimmune effector memory T cells: the bad and the good

Immunological memory is a hallmark of adaptive immunity, a defense mechanism endowed to vertebrates during evolution. However, an autoimmune pathogenic role of memory lymphocytes is also emerging with accumulating evidence, despite reasonable skepticism on their existence in a chronic setting of autoimmune damage. It is conceivable that autoimmune memory would be particularly harmful since memory cells would constantly "remember" and attack the body's healthy tissues. It is even more detrimental given the resistance of memory T cells to immunomodulatory therapies. In this review, we focus on self-antigen-reactive CD(+) effector memory T (TEM) cells, surveying the evidence for the role of the T(EM) compartment in autoimmune pathogenesis. We will also discuss the role of T(EM) cells in chronic and acute infectious disease settings and how they compare to their counterparts in autoimmune diseases. With their long-lasting potency, the autoimmune T(EM) cells could also play a critical role in anti-tumor immunity, which may be largely based on their reactivity to self-antigens. Therefore, although autoimmune T(EM) cells are "bad" due to their role in relentless perpetration of tissue damage in autoimmune disease settings, they are unlikely a by-product of industrial development along the modern surge of autoimmune disease prevalence. Rather, they may be a product of evolution for their "good" in clearing damaged host cells in chronic infections and malignant cells in cancer settings.

Changes in T lymphocyte subsets in mice with CT26 colon tumors after treatment with donor lymphocyte infusion

The objective of this study was to detect changes in T lymphocyte subpopulations in mice with CT26 subcutaneous colon cancer after treatment with donor lymphocyte infusion (DLI) and cyclophosphamide (CP) chemotherapy. A colon cancer model was established by subcutaneous injection of CT26 carcinoma cells into BALB/C mice. The mice were randomized into different treatment groups. We recorded survival times, tumor growth inhibition rates, histopathological changes, and T lymphocyte subsets in peripheral blood of the mice. Mice treated with DLI and CP survived 33.5 ± 5.02 days, which was significantly longer than the survival time of untreated control mice (16.7 ± 2.98 days, P < 0.01). In addition, the tumor inhibitory rate was higher in mice treated with DLI and CP (89.3 %) than that in mice treated with CP or DLI alone (67.1 and 34.5 %, respectively). There were higher levels of T lymphocytes that were CD3(+) and CD4(+) in mice treated with DLI alone or the combination of CP and DLI (P < 0.05), and the ratio of CD4(+)/CD8(+) cells was significantly improved in these mice (P < 0.05). DLI combined with chemotherapy significantly prolonged survival and inhibited tumor growth in mice with CT26 colon cancer. This treatment might also improve immune function in these mice. Donor spleen cells that include high numbers of allogeneic lymphocytes and a few stem cells could induce a graft-versus-tumor effect, leading to elimination of residual cancer cells. This indicates that it is potentially a feasible adoptive cellular immunotherapy strategy for the management of solid tumors.

Autoimmunity as a double agent in tumor killing and cancer promotion

Cancer immunotherapy through manipulation of the immune system holds great potential for the treatment of human cancers. However, recent trials targeting the negative immune regulators cytotoxic T-lymphocyte antigen 4, programed death 1 (PD-1), and PD-1 receptor ligand (PD-L1) demonstrated that clinically significant antitumor responses were often associated with the induction of autoimmune toxicity. This finding suggests that the same immune mechanisms that elicit autoimmunity may also contribute to the destruction of tumors. Given the fact that the immunological identity of tumors might be largely an immunoprivileged self, autoimmunity may not represent a wholly undesirable outcome in the context of cancer immunotherapy. Rather, targeted killing of cancer cells and autoimmune damage to healthy tissues may be intricately linked through molecular mechanisms, in particular inflammatory cytokine signaling. On the other hand, since chronic inflammation is a well-recognized condition that promotes tumor development, it appears that autoimmunity can be a "double agent" in mediating either pro-tumor or antitumor effects. This review surveys the tumor-promoting and tumoricidal activities of several prominent cytokines: IFN-γ, TNF-α, TGF-β, IL-17, IL-23, IL-4, and IL-13, produced by three major subsets of T helper cells that interact with innate immune cells. Many of these cytokines exert divergent and seemingly contradictory effects on cancer development in different human and animal models, suggesting a high degree of context dependence in their functions. We hypothesize that these inflammatory cytokines could mediate a feedback loop of autoimmunity, antitumor immunity, and tumorigenesis. Understanding the diverse and paradoxical roles of cytokines from autoimmune responses in the setting of cancer will advance the long-term goal of improving cancer immunotherapy, while minimizing the hazards of immune-mediated tissue damage and the possibility of de novo tumorigenesis, through proper monitoring and preventive measures.

From biomarkers to a clue of biology: a computation-aided perspective of immune gene expression profiles in human type 1 diabetes

Dysregulated expression of key immune genes may cause breakdown of immunological tolerance and development of autoimmune disorders such as type 1 diabetes (T1D). General immune insufficiencies have also been implicated as a trigger of autoimmunity, due to their potential impact on immune homeostasis. Recent studies have detected evidence of systemic reduction in immune gene expression in long-term diabetic patients but the changes were not present before or at T1D onset. The changes could not be merely correlated with alteration in metabolic parameters. The studies also identified a dynamic expression pattern of several well-known as well as little-studied, immune-related genes during the course of T1D. An intriguing “ratio profile” of immune regulatory genes, such as CTLA4 and members of the S100 family, versus “baseline” immune genes, such as CD3G, prompted us to further examine immune gene expression relationships for a set of molecules representing T cells, B cells, and myeloid cells. No evidence was found to suggest an overall breach of tolerance equilibrium in T1D. Perplexingly, patients with long-term T1D presented a gene expression profile that was surprisingly more coordinated in analyses of “networking” relationship. Computational analyses of the “ratio profiles” or “relationship profiles” of immune gene expression might provide a clue for further studies of immunobiology in human T1D and other autoimmune diseases, as to how the profiles may be related to the pathogenic cause of the disease, to the effect of the diseases on immune homeostasis, or to an immunological process associated with the course of the diseases but is neither a direct cause nor a direct effect of the diseases.

Adoptive transfer of allogeneic liver sinusoidal endothelial cells specifically inhibits T-cell responses to cognate stimuli

Although it is well known that liver allografts are often accepted by recipients, leading to donor-specific tolerance of further organ transplants, the underlying mechanisms remain unclear. We had previously used an in vitro model and showed that mouse liver sinusoidal endothelial cells (LSECs) selectively suppress allospecific T-cells across major histocompatibility complex (MHC) barriers. In the present study, we established an in vivo model for evaluating the immunomodulatory effects of allogeneic LSECs on corresponding T-cells. Allogeneic BALB/cA LSECs were injected intraportally into recombination activating gene 2 γ-chain double-knockout (RAG2/gc-KO, H-2(b)) mice lacking T, B, and natural killer (NK) cells. In order to facilitate LSEC engraftment, the RAG2/gc-KO mice were injected intraperitoneally with monocrotaline 2 days before the adoptive transfer of LSECs; this impaired the host LSECs, conferring a proliferative advantage to the transplanted LSECs. After orthotopic allogeneic LSEC engraftment, the RAG2/gc-KO mice were immune reconstituted intravenously with C57BL/6 splenocytes. After immune reconstitution, mixed lymphocyte reaction (MLR) assay using splenocytes from the recipients revealed that specific inhibition of host CD4(+) and CD8(+) T-cell proliferation was greater in response to allostimulation with irradiated BALB/cA splenocytes rather than to stimulation with irradiated third party SJL/jorllco splenocytes. This inhibitory effect was attenuated by administering anti-programmed death ligand 1 (PD-L1) monoclonal antibody during immune reconstitution in the above-mentioned mice, but not in RAG2/gc-KO mice engrafted with Fas ligand (FasL)-deficient BALB/cA LSECs. Furthermore, engraftment of allogeneic BALB/cA LSECs significantly prolonged the survival of subsequently grafted cognate allogeneic BALB/cA hearts in RAG2/gc-KO mice immune reconstituted with bone marrow transplantation from C57BL/6 mice. In conclusion, murine LSECs have been proven capable of suppressing T-cells with cognate specificity for LSECs in an in vivo model. The programmed death 1/PD-L1 pathway is likely involved in these suppressive effects.

Autologous mesenchymal stem cells prevent transplant arteriosclerosis by enhancing local expression of interleukin-10, interferon-γ, and indoleamine 2,3-dioxygenase

Transplant arteriosclerosis (TA) remains the major limitation of long-term graft survival in heart transplantation despite the advances in immunosuppressants. Mesenchymal stem cells (MSCs) have been demonstrated to suppress allogeneic immune responses by numerous in vitro studies. However, the immunomodulatory effects of MSCs in vivo are controversial and the underlying molecular mechanisms are not conclusive. In this study, we investigated the therapeutic potential of autologous bone marrow-derived MSCs on TA in a porcine model of femoral artery transplantation. MSCs or saline were injected into the soft tissue surrounding the arterial grafts immediately postanastomosis. Four weeks after transplantation, neointimal formation increased significantly in untreated allografts compared with the MSC-treated grafts as assessed by intravascular ultrasound (maximum luminal area stenosis: 40 ± 12% vs. 18 ± 6%, p < 0.001). Grafts harvested at 4 weeks showed dense perivascular lymphocyte infiltration accompanied by significant intimal hyperplasia in the untreated but not in the MSC-treated allografts. Serial angiographic examination showed that all of the untreated allografts became occluded at the 8th week whereas the majority of the MSC-treated grafts remained patent at the 12th week posttransplantation (n = 12 each group, p < 0.001). Quantitative PCR analysis revealed that Foxp3 expression was comparable between the untreated and the MSC-treated groups. However, expression of interleukin-10 (IL-10), interferon-γ (IFN-γ), and indoleamine 2,3-dioxygenase (IDO) was increased significantly in the MSC-treated allografts compared with that in the allograft controls (p = 0.021 for IL-10, p = 0.003 for IFN-γ, and p = 0.008 for IDO). In conclusion, local delivery of autologous MSCs alleviates TA by inducing allograft tolerance via enhanced expression of IL-10, IFN-γ, and IDO but not Foxp3-positive cells in the vessel wall. These results suggest that MSCs induce immune tolerance by activating the type 1 regulatory T-like cells.

B7-H4 induces donor-specific tolerance in mouse islet allografts

Negative cosignaling molecules play an important role in regulating T-cell responses to alloantigen stimulation. We recently reported that adenoviral-mediated transduction of islet allografts with B7-H4 inhibits allograft rejection. In this study, we investigate the mechanism for B7-H4-induced prolongation of mouse islet allograft survival. Streptozotocin-induced diabetic C57BL/6 mice were rendered normoglycemic by renal subcapsular implants of B7-H4-transduced BALB/c islets. Grafts and spleens were removed after days 2, 10, and 60 (n = 8 each) for characterization of kinetics of Foxp3 and interleukin 10 (IL-10) expression. Mixed lymphocyte reaction (MLR) was done at day 60. Ten mice were subjected to nephrectomy at 60 days and then five were implanted with secondary BALB/c islets and five were given third-party CBA/J islets. An increase in Foxp3 and IL-10 mRNA expression was detected in recipients' spleens at day 60 and this was associated with increased quantities of Foxp3(+) cells. Splenocytes at day 60 showed hyporesponsiveness during MLR to alloantigen stimulation. Proliferation was partially restored after CD25(+) T-cell depletion. Secondary BALB/c islets survived for 79 ± 29 days compared with 21 ± 3.6 days for CBA/J islets (p < 0.001). Local expression of B7-H4 induces long-term unresponsiveness to donor-specific alloantigens, and is associated with T regulatory cells, suggesting the development of tolerance.

Myeloid derived suppressor cells in transplantation

Myeloid derived suppressor cells (MDSC) are a heterogeneous population of hematopoietic derived cell precursors that can suppress immune responses in a variety of inflammatory settings. Here we review recent studies detailing expansion of phenotypically and functionally disparate MDSC. Findings related to MDSC accumulation, activation, and mechanisms utilized in immune suppression are presented. Further, we discuss recent reports that suggest MDSC are expanded during transplantation and that modulation of MDSC can participate in preventing graft rejection.

Molecular cloning, expression and characterization of the functional domain of CTLA4 from the rhesus monkey, Macaca mulatta

Cytotoxic T lymphocyte-associated antigen 4 (CTLA4) is a potent inhibitor of T cell activation. The genes encoding the membrane and soluble forms of Macaca mulatta CTLA4 (mmCTLA4) were isolated from peripheral blood mononuclear cells (PBMCs). The predicted mmCTLA4 protein is nearly identical to human CTLA4 (hCTLA4), with the exception of a serine instead of an asparagine residue at position 49 and a leucine instead of a methionine residue at position 141 of its extracellular domain. The fusion protein mmCTLA4Ig, containing the extracellular domain of mmCTLA4 and the constant region of the human IgG1 antibody, was expressed in Pichia pastoris. The mmCTLA4Ig produced by P. pastoris exhibited specific binding to human B7-positive Raji cells that could be inhibited by competitive binding of hCTLA4Ig. MmCTLA4Ig and hCTLA4Ig could comparably suppress the proliferation of lymphocytes derived from rhesus monkeys, humans, or mice that had been stimulated either by concanavalin A (Con A) or allogeneic cells. These results suggest that mmCTLA4 is a negative regulator of T cell activation and that mmCTLA4Ig may be useful for immunotherapy of immunologic diseases in the rhesus monkey.

Induction of self-antigen-specific Foxp3+ regulatory T cells in the periphery by lymphodepletion treatment with anti-mouse thymocyte globulin in mice

Lymphodepletion therapies are increasingly tested for controlling immune damage. One appealing premise for such a therapy is that it may 'reboot' the immune system and restore immune tolerance. However, the tolerogenic potential of lymphodepletion therapies remains controversial. The debate is exemplified by conflicting evidence from the studies of anti-thymocyte globulin (ATG), a prototype of immunodepleting drugs, in particular on whether it induces CD4(+) CD25(+) Foxp3(+) regulatory T (Treg) cells. To understand the impact of ATG on T cells at a clonal level in vivo, we studied the effect of anti-mouse thymocyte globulin (mATG) in a reductionist model in which the T-lymphocyte repertoire consists of a single clone of pathogenic T effector (Teff) cells specific to a physiological self-antigen. The mATG treatment led to peripheral induction of antigen-specific Treg cells from an otherwise monoclonal Teff repertoire, independent of thymic involvement. The de novo induction of Treg cells occurred consistently in local draining lymph nodes, and persistence of induced Treg cells in blood correlated with long-term protection from autoimmune destruction. This study provides in vivo evidence for clonal conversion from a pathogenic self-antigen-specific Teff cell to a Treg cell in the setting of immunodepletion therapies.

Rapamycin generates graft-homing murine suppressor CD8(+) T cells that confer donor-specific graft protection

It has been reported that rapamycin (RPM) can induce de novo conversion of the conventional CD4(+)Foxp3(-) T cells into CD4(+)Foxp3(+) regulatory T cells (iTregs) in transplantation setting. It is not clear whether RPM can similarly generate suppressor CD8(+) T cells to facilitate graft acceptance. In this study, we investigated the ability of short-term RPM treatment in promoting long-term acceptance (LTA) of MHC-mismatched skin allografts by generating a CD8(+) suppressor T-cell population. We found that CD4 knockout (KO) mice (in C57BL/6 background, H-2(b)) can promptly reject DBA/2 (H-2(d)) skin allografts with mean survival time (MST) being 13 days (p < 0.01). However, a short course RPM treatment in these animals induced LTA with graft MST longer than 100 days. Adoptive transfer of CD8(+) T cells from LTA group into recombination-activating gene 1 (Rag-1)-deficient mice provided donor-specific protection of DBA/2 skin grafts against cotransferred conventional CD8(+) T cells. Functionally active immunoregulatory CD8(+) T cells also resided in donor skin allografts. Eighteen percent of CD8(+) suppressor T cells expressed CD28 as measured by flow cytometry, and produced reduced levels of IFN-γ, IL-2, and IL-10 in comparison to CD8(+) effector T cells as measured by ELISA. It is unlikely that CD8(+) suppressor T cells mediated graft protection via IL-10, as IL-10/Fc fusion protein impaired RPM-induced LTA in CD4 KO mice. Our data supported the notion that RPM-induced suppressor CD8(+) T cells home to the allograft and exert donor-specific graft protection.

Alternatively Expressed Genes Identified in the CD4+ T Cells of Allograft Rejection Mice

Allograft rejection is a leading cause for the failure of allotransplantation. CD4+ T cells play critical roles in this process. The identification of genes that alternatively expressed in CD4+ T cells during allograft rejection will provide critical information for studying the mechanism of allograft rejection, finding specific gene markers for monitoring, predicting allograft rejection, and opening new ways to regulate and prevent allograft rejection. Here, we established allograft and isograft transplantation models by adoptively transferring wild-type BALB/c mouse CD4+ T cells into severe combined immunodeficient (SCID) mice with a C57BL/6 or BALB/c mouse skin graft. Using the whole transcriptome sequencing-based serial analysis of gene expression (SAGE) technology, we identified 97 increasingly and 88 decreasingly expressed genes that may play important roles in allograft rejection and tolerance. Functional classification of these genes shows that apoptosis, transcription regulation, cell growth and maintenance, and signal transduction are among the frequently changed functional groups. This study provides a genome-wide view for the candidate genes of CD4+ T cells related to allotransplantation, and this report is a good resource for further microarray studies and for identifying the specific markers that are associated with clinical organ transplantations.

The time is crucial for ex vivo expansion of T regulatory cells for therapy

Ex vivo expanded CD4(+)CD25(high)CD127(-) T regulatory cells (Tregs) are recognized as a promising candidate for immunosuppressive therapy in humans. However, due to the plasticity of Tregs lineage and artificial environment present during ex vivo expansion, Tregs easily lose suppressive activity. Here, we followed expanding CD4(+)CD25(high)CD127(-) Tregs and their naive (CD45RA(+)) and memory-like (CD45RA(-)) subsets in order to establish the best conditions of the expansion. We found that, regardless of the phenotype sorted, expanding Tregs were undergoing changes resembling homeostatic proliferation and transformed into effector memory-like cells which produced not only suppressive interleukin-10 (IL-10) but also IL-6, IL-17, and interferon-γ (IFN-γ). With the time ex vivo, Tregs were losing the expression of FoxP3 and suppressive activity both when stimulated and when at rest. The only variable that helped preserve suppressive abilities of Tregs was the limitation of the time of ex vivo cultures to 2 weeks only. According to our study, the highest number of highly suppressive Tregs could be yielded with CD4(+)CD25(high)CD127(-) Tregs cultured no longer than 2 weeks. Thorough quality check, preferentially with the assessment of FoxP3 expression and IFN-γ suppression assay, should be applied to assess suppressive activity of the cells.

Replacement of liver parenchyma in analbuminemic rats with allogenic hepatocytes is facilitated by intrabone marrow-bone marrow transplantation

Although hepatocyte transplantation (HCTx) is expected to become a useful therapy for human liver diseases, allogenic hepatocytes still tend to be rejected within a short period due to host immunosurveillance. In the present study, we investigated the effect of prior bone marrow transplantation (BMTx) for the engraftment of allogenic hepatocytes using the analbuminemic rat transplantation model. The hepatocytes of Lewis (LEW) rats were not accepted in the liver of retrorsine (RS)/partial hepatectomy (PH)-treated analbuminemic F344 (F344-alb) rats, which express the disparate major histocompatibility complex (MHC) against that of LEW rats. Prior BMTx with the LEW bone marrow cells (BMCs) after sublethal irradiation achieved acceptance and repopulation of LEW hepatocytes in the liver of the RS/PH-treated F344-alb rats, associated with elevation of serum albumin. The replacement of hepatic parenchyma with albumin positive (Alb(+)) donor hepatocytes and elevation of serum albumin levels were dependent on the bone marrow reconstitution by donor BMCs, which was more efficiently achieved by intrabone marrow (IBM)-BMTx than by intravenous (IV)-BMTx. Our results demonstrate that efficient bone marrow reconstitution by IBM-BMTx enables the replacement of the hepatic parenchyma with allogenic hepatocytes in RS/PH-treated analbuminemic rats without immunosuppressants.