Differential expression of Smad7 transcripts identifies the CD4+CD45RChigh regulatory T cells that mediate type V collagen-induced tolerance to lung allografts

Extracellular Vesicles Mediate Immune Responses to Tissue-Associated Self-Antigens: Role in Solid Organ Transplantations

Transplantation is a treatment option for patients diagnosed with end-stage organ diseases; however, long-term graft survival is affected by rejection of the transplanted organ by immune and nonimmune responses. Several studies have demonstrated that both acute and chronic rejection can occur after transplantation of kidney, heart, and lungs. A strong correlation has been reported between de novo synthesis of donor-specific antibodies (HLA-DSAs) and development of both acute and chronic rejection; however, some transplant recipients with chronic rejection do not have detectable HLA-DSAs. Studies of sera from such patients demonstrate that immune responses to tissue-associated antigens (TaAgs) may also play an important role in the development of chronic rejection, either alone or in combination with HLA-DSAs. The synergistic effect between HLA-DSAs and antibodies to TaAgs is being established, but the underlying mechanism is yet to be defined. We hypothesize that HLA-DSAs damage the transplanted donor organ resulting in stress and leading to the release of extracellular vesicles, which contribute to chronic rejection. These vesicles express both donor human leukocyte antigen (HLA) and non-HLA TaAgs, which can activate antigen-presenting cells and lead to immune responses and development of antibodies to both donor HLA and non-HLA tissue-associated Ags. Extracellular vesicles (EVs) are released by cells under many circumstances due to both physiological and pathological conditions. Primarily employing clinical specimens obtained from human lung transplant recipients undergoing acute or chronic rejection, our group has demonstrated that circulating extracellular vesicles display both mismatched donor HLA molecules and lung-associated Ags (collagen-V and K-alpha 1 tubulin). This review focuses on recent studies demonstrating an important role of antibodies to tissue-associated Ags in the rejection of transplanted organs, particularly chronic rejection. We will also discuss the important role of extracellular vesicles released from transplanted organs in cross-talk between alloimmunity and autoimmunity to tissue-associated Ags after solid organ transplantation.

Screening and identification of key regulatory connections and immune cell infiltration characteristics for lung transplant rejection using mucosal biopsies

This study aimed to explore key regulatory connections underlying lung transplant rejection. The differentially expressed genes (DEGs) between rejection and stable lung transplantation (LTx) samples were screened using R package limma, followed by functional enrichment analysis and protein-protein interaction network construction. Subsequently, a global triple network, including miRNAs, mRNAs, and transcription factors (TFs), was constructed. Furthermore, immune cell infiltration characteristics were analyzed to investigate the molecular immunology of lung transplant rejection. Finally, potential drug-target interactions were generated. In brief, 739 DEGs were found between rejection and stable LTx samples. PTPRC, IL-6, ITGAM, CD86, TLR8, TYROBP, CXCL10, ITGB2, and CCR5 were defined as hub genes. Eight TFs, including STAT1, SPIB, NFKB1, SPI1, STAT5A, RUNX1, VENTX, and BATF, and five miRNAs, including miR-335-5p, miR-26b-5p, miR-124-3p, miR-1-3p, and miR-155-5p, were involved in regulating hub genes. The immune cell infiltration analysis revealed higher proportions of activated memory CD4 T cells, follicular helper T cells, γδ T cells, monocytes, M1 and M2 macrophages, and eosinophils in rejection samples, besides lower proportions of resting memory CD4 T cells, regulatory T cells, activated NK cells, M0 macrophages, and resting mast cells. This study provided a comprehensive perspective of the molecular co-regulatory network underlying lung transplant rejection.

Lung Injury and Loss of Regulatory T Cells Primes for Lung-Restricted Autoimmunity

Lung transplantation is a life-saving therapy for several end-stage lung diseases. However, lung allografts suffer from the lowest survival rate predominantly due to rejection. The pathogenesis of alloimmunity and its role in allograft rejection has been extensively studied and multiple approaches have been described to induce tolerance. However, in the context of lung transplantation, dysregulation of mechanisms, which maintain tolerance against self-antigens, can lead to lung-restricted autoimmunity, which has been recently identified to drive the immunopathogenesis of allograft rejection. Indeed, both preexisting as well as de novo lung-restricted autoimmunity can play a major role in the development of lung allograft rejection. The three most widely studied lung-restricted self-antigens include collagen type I, collagen type V, and k-alpha 1 tubulin. In this review, we discuss the role of lung-restricted autoimmunity in the development of both early as well as late lung allograft rejection and recent literature providing insight into the development of lung-restricted autoimmunity through the dysfunction of immune mechanisms which maintain peripheral tolerance.

A lipidated peptide of Mycobacterium tuberculosis resuscitates the protective efficacy of BCG vaccine by evoking memory T cell immunity

BACKGROUND

The current BCG vaccine induces only short-term protection against Mycobacterium tuberculosis (Mtb), suggesting its failure to generate long-lasting memory T cells. Previously, we have demonstrated that a self-adjuvanting peptide of Mtb (L91), successfully generated enduring memory Th1 cells. Consequently, we investigated if L91 was able to recuperate BCG potency in perpetuating the generation of memory T cells and protection against Mtb infected mice.

METHODS

In the present study, we evaluated the potency of a self adjuvanting Mtb peptide vaccine L91 in invigorating BCG immune response against Mtb in mice. Female BALB/c mice were immunized with BCG. Later, they were boosted twice with L91 or an antigenically irrelevant lipidated influenza virus hemagglutinin peptide (LH). Further, PBMCs obtained from BCG vaccinated healthy subjects were cultured in vitro with L91. T cell responses were determined by surface markers and intracellular cytokine staining. Secretion of cytokines was estimated in the culture supernatants (SNs) by ELISA.

RESULTS

Compared to the BCG-vaccinated controls, L91 booster significantly enhanced the percentage of memory Th1 cells and Th17 cells and reduced the mycobacterial burden in BCG primed and L91-boosted (BCG-L91) group, even after 229 days of BCG vaccination. Further, substantial augmentation in the central (CD44^hiCD62L^hiCD127^hi) and effector memory (CD44^hiCD62L^loCD127^lo) CD4 T cells was detected. Furthermore, greater frequency of polyfunctional Th1 cells (IFN-γ⁺TNF-α⁺) and Th17 cells (IFN-γ⁺IL-17A⁺) was observed. Importantly, BCG-L91 successfully prevented CD4 T cells from exhaustion by decreasing the expression of PD-1 and Tim-3. Additionally, augmentation in the frequency of Th1 cells, Th17 cells and memory CD4 T cells was observed in the PBMCs of the BCG-vaccinated healthy individuals following in vitro stimulation with L91.

CONCLUSIONS

Our study demonstrated that L91 robustly reinvigorate BCG potency to invoke enduring protection against Mtb. This novel vaccination stratagem involving BCG-priming followed by L91-boosting can be a future prophylactic measure to control TB.

Lung-Restricted Antibodies Mediate Primary Graft Dysfunction and Prevent Allotolerance after Murine Lung Transplantation

Over one-third of lung recipients have preexisting antibodies against lung-restricted antigens: collagen (Col) type V and K-α1 tubulin (KAT). Although clinical studies have shown association of these antibodies with primary graft dysfunction (PGD), their biological significance remains unclear. We tested whether preexisting lung-restricted antibodies can mediate PGD and prevent allotolerance. A murine syngeneic (C57BL/6) or allogeneic (C57BL/6 to BALB/c) left lung transplantation model was used. Rabbit polyclonal antibodies were produced against KAT and Col-V and injected pretransplantation. T cell frequency was analyzed using enzyme-linked immunospot, whereas alloantibodies were determined using flow cytometry. Wet:dry ratio, arterial oxygenation, and histology were used to determine PGD. Preexisting Col-V or KAT, but not isotype control, antibodies lead to dose-dependent development of PGD after syngeneic lung transplantation, as evidenced by poor oxygenation and increased wet:dry ratio. Histology confirmed alveolar and capillary edema. The native right lung remained unaffected. Epitope spreading was observed where KAT antibody treatment led to the development of IL-17-producing CD4⁺ T cells and humoral response against Col-V, or vice versa. In contrast, isotype control antibody failed to induce Col-V- or KAT-specific cellular or humoral immunity. In addition, none of the mice developed immunity against a non-lung antigen, collagen type II. Preexisting lung-restricted antibodies, but not isotype control, prevented development of allotolerance using the MHC-related 1 and cytotoxic T-lymphocyte-associated protein 4-Ig regimen. Lung-restricted antibodies can induce both early and delayed lung graft dysfunction. These antibodies can also cause spreading of lung-restricted immunity and promote alloimmunity. Antibody-directed therapy to treat preexisting lung-restricted antibodies might reduce PGD after lung transplantation.

Lung Injury Combined with Loss of Regulatory T Cells Leads to De Novo Lung-Restricted Autoimmunity

More than one third of patients with chronic lung disease undergoing lung transplantation have pre-existing Abs against lung-restricted self-Ags, collagen type V (ColV), and k-α1 tubulin (KAT). These Abs can also develop de novo after lung transplantation and mediate allograft rejection. However, the mechanisms leading to lung-restricted autoimmunity remain unknown. Because these self-Ags are normally sequestered, tissue injury is required to expose them to the immune system. We previously showed that respiratory viruses can induce apoptosis in CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs), the key mediators of self-tolerance. Therefore, we hypothesized that lung-tissue injury can lead to lung-restricted immunity if it occurs in a setting when Tregs are impaired. We found that human lung recipients who suffer respiratory viral infections experienced a decrease in peripheral Tregs. Pre-existing lung allograft injury from donor-directed Abs or gastroesophageal reflux led to new ColV and KAT Abs post respiratory viral infection. Similarly, murine parainfluenza (Sendai) respiratory viral infection caused a decrease in Tregs. Intratracheal instillation of anti-MHC class I Abs, but not isotype control, followed by murine Sendai virus infection led to development of Abs against ColV and KAT, but not collagen type II (ColII), a cartilaginous protein. This was associated with expansion of IFN-γ-producing CD4(+) T cells specific to ColV and KAT, but not ColII. Intratracheal anti-MHC class I Abs or hydrochloric acid in Foxp3-DTR mice induced ColV and KAT, but not ColII, immunity, only if Tregs were depleted using diphtheria toxin. We conclude that tissue injury combined with loss of Tregs can lead to lung-tissue-restricted immunity.

The Active Form of Vitamin D Transcriptionally Represses Smad7 Signaling and Activates Extracellular Signal-regulated Kinase (ERK) to Inhibit the Differentiation of a Inflammatory T Helper Cell Subset and Suppress Experimental Autoimmune Encephalomyelitis

The ability of the active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), to transcriptionally modulate Smads to inhibit Th17 differentiation and experimental autoimmune encephalomyelitis (EAE) has not been adequately studied. This study reports modulation of Smad signaling by the specific binding of the VDR along with its heterodimeric partner RXR to the negative vitamin D response element on the promoter of Smad7, which leads to Smad7 gene repression. The vitamin D receptor-mediated increase in Smad3 expression partially explains the IL10 augmentation seen in Th17 cells. Furthermore, the VDR axis also modulates non-Smad signaling by activating ERK during differentiation of Th17 cells, which inhibits the Th17-specific genes il17a, il17f, il22, and il23r. In vivo EAE experiments revealed that, 1,25(OH)2D3 suppression of EAE correlates with the Smad7 expression in the spleen and lymph nodes. Furthermore, Smad7 expression also correlates well with IL17 and IFNγ expression in CNS infiltered inflammatory T cells. We also observed similar gene repression of Smad7 in in vitro differentiated Th1 cells when cultured in presence of 1,25(OH)2D3. The above canonical and non-canonical pathways in part address the ability of 1,25(OH)2D3-VDR to inhibit EAE.

The need for a new animal model for chronic rejection after lung transplantation

The single most important cause of late mortality after lung transplantation is obliterative bronchiolitis (OB), clinically characterized by a decrease in lung function and morphologically by characteristic changes. Recently, new insights into its pathogenesis have been acquired: risk factors have been identified and the use of azithromycin showed a dichotomy with at least 2 different phenotypes of bronchiolitis obliterans syndrome (BOS). It is clear that a good animal model is indispensable to further dissect and unravel the pathogenesis of BOS. Many animal models have been developed to study BOS but, so far, none of these models truly mimics the human situation. Looking at the definition of BOS, a good animal model implies histological OB lesions, possibility to measure lung function, and airway inflammation. This review sought to discuss, including pros and cons, all potential animal models that have been developed to study OB/BOS. It has become clear that a new animal model is needed; recent developments using an orthotopic mouse lung transplantation model may offer the answer because it mimics the human situation. The genetic variants among this species may open new perspectives for research into the pathogenesis of OB/BOS.

Caerulomycin A enhances transforming growth factor-β (TGF-β)-Smad3 protein signaling by suppressing interferon-γ (IFN-γ)-signal transducer and activator of transcription 1 (STAT1) protein signaling to expand regulatory T cells (Tregs)

Cytokines play a very important role in the regulation of immune homeostasis. Regulatory T cells (Tregs) responsible for the generation of peripheral tolerance are under the tight regulation of the cytokine milieu. In this study, we report a novel role of a bipyridyl compound, Caerulomycin A (CaeA), in inducing the generation of Tregs. It was observed that CaeA substantially up-regulated the pool of Tregs, as evidenced by an increased frequency of CD4(+) Foxp3(+) cells. In addition, CaeA significantly suppressed the number of Th1 and Th17 cells, as supported by a decreased percentage of CD4(+)/IFN-γ(+) and CD4(+)/IL-17(+) cells, respectively. Furthermore, we established the mechanism and observed that CaeA interfered with IFN-γ-induced STAT1 signaling by augmenting SOCS1 expression. An increase in the TGF-β-mediated Smad3 activity was also noted. Furthermore, CaeA rescued Tregs from IFN-γ-induced inhibition. These results were corroborated by blocking Smad3 activity, which abolished the CaeA-facilitated generation of Tregs. In essence, our results indicate a novel role of CaeA in inducing the generation of Tregs. This finding suggests that CaeA has enough potential to be considered as a potent future drug for the treatment of autoimmunity.

Early administration of FTY720 prevents chronic airway as well as vascular destruction in experimental rat lung transplantation

BACKGROUND

Chronic rejection (CR) in terms of bronchiolitis obliterans (BO) and vascular sclerosis (VS) still represents the major obstacle for pulmonary graft survival in the medium and long term course after lung transplantation (LTX). Aside from nonspecific stimuli, early acute rejection (AR) seems to be causative especially in cases of a late diagnosis or inadequate treatment. This study investigated the effects of FTY720, a new immunosuppressant that promotes lymphocyte sequestration into lymph nodes and Peyer's patches, on the development of CR after experimental LTX.

METHODS

A total of 50 rats underwent allogenic (F344-to-WKY) and syngenic (WKY-to-WKY) left LTX. Group 1 animals had no treatment. Group 2 animals were administered FTY720 (3 mg/kg body weight per day) at the maximum time of AR (day 14) and continued up to day 100 after LTX. Group 3 animals were treated with the same dosage of FTY720 from day 0 to 100. The grades of AR and CR were classified according to the criteria of the International Society for Heart and Lung Transplantation.

RESULTS

Within 14 days after allogenic LTX, all nontreated rats developed early AR followed by severe CR with VS and BO. Similar data were observed for FTY720 treatment of existing AR (group 2). Only early administration of FTY720 (at the time of LTX) significantly reduced the proportion of animals with severe acute vascular rejection (P < .001). However, all of these allografts showed high-grade acute airway inflammation. After long-term application, the chronic inflammatory response was absent; none of the allografts developed BO and VS.

CONCLUSION

Only application of FTY720 immediately after LTX prevented lymphocyte recirculation and lung injury.

Lung transplantation

Lung transplantation may be the only intervention that can prolong survival and improve quality of life for those individuals with advanced lung disease who are acceptable candidates for the procedure. However, these candidates may be extremely ill and require ventilator and/or circulatory support as a bridge to transplantation, and lung transplantation recipients are at risk of numerous post-transplant complications that include surgical complications, primary graft dysfunction, acute rejection, opportunistic infection, and chronic lung allograft dysfunction (CLAD), which may be caused by chronic rejection. Many advances in pre- and post-transplant management have led to improved outcomes over the past decade. These include the creation of sound guidelines for candidate selection, improved surgical techniques, advances in donor lung preservation, an improving ability to suppress and treat allograft rejection, the development of prophylaxis protocols to decrease the incidence of opportunistic infection, more effective therapies for treating infectious complications, and the development of novel therapies to treat and manage CLAD. A major obstacle to prolonged survival beyond the early post-operative time period is the development of bronchiolitis obliterans syndrome (BOS), which is the most common form of CLAD. This manuscript discusses recent and evolving advances in the field of lung transplantation.

Regulatory T cells and pulmonary hypertension

Pulmonary hypertension (PH) is a disease of high lethality arising from numerous causes. For a significant subset of PH patients, autoimmune biomarkers or frank autoimmune disease are simultaneously present, but the extent to which lung inflammation contributes to PH is unknown. However, emerging experimental and clinical evidence suggests that immune dysregulation may lead to the propagation of vascular injury and PH. A recent preclinical study demonstrated that regulatory T cells are important mediators normally enlisted to control inflammation and that, if absent or dysfunctional, may predispose to the development of PH.

An important role for autoimmunity in the immunopathogenesis of chronic allograft rejection

Organ transplantation is the treatment of choice for patients with end-stage organ dysfunction. In spite of advances in understanding of donor and recipient physiology, organ preservation, operative techniques and immunosuppression, long-term graft survival still remains a major problem primarily due to chronic rejection. Alloimmune responses to mismatched major histocompatibility antigens have been implicated as an important factor leading to rejection. However, there is increasing evidence pointing towards cross-talk between the alloimmune and autoimmune responses creating a local inflammatory milieu, which eventually leads to fibrosis and occlusion of the lumen in the transplanted organ i.e. chronic rejection. In this review, we will discuss recent studies and emerging concepts for the interdependence of alloimmune and autoimmune responses in the immunopathogenesis of chronic allograft rejection. The role of autoimmunity in the development of chronic rejection is an intriguing and exciting area of research in the field of solid-organ transplantation with a significant potential to develop novel therapeutic strategies towards preventing chronic allograft rejection.

Regulatory T cells limit vascular endothelial injury and prevent pulmonary hypertension

RATIONALE

Pulmonary arterial hypertension (PAH) is an incurable disease associated with viral infections and connective tissue diseases. The relationship between inflammation and disease pathogenesis in these disorders remains poorly understood.

OBJECTIVE

To determine whether immune dysregulation due to absent T-cell populations directly contributes to the development of PAH.

METHODS AND RESULTS

Vascular endothelial growth factor receptor 2 (VEGFR2) blockade induced significant pulmonary endothelial apoptosis in T-cell-deficient rats but not in immune-reconstituted (IR) rats. T cell-lymphopenia in association with VEGFR2 blockade resulted in periarteriolar inflammation with macrophages, and B cells even prior to vascular remodeling and elevated pulmonary pressures. IR prevented early inflammation and attenuated PAH development. IR with either CD8 T cells alone or with CD4-depleted spleen cells was ineffective in preventing PAH, whereas CD4-depleting immunocompetent euthymic animals increased PAH susceptibility. IR with either CD4(+)CD25(hi) or CD4(+)CD25(-) T cell subsets prior to vascular injury attenuated the development of PAH. IR limited perivascular inflammation and endothelial apoptosis in rat lungs in association with increased FoxP3(+), IL-10- and TGF-β-expressing CD4 cells, and upregulation of pulmonary bone morphogenetic protein receptor type 2 (BMPR2)-expressing cells, a receptor that activates endothelial cell survival pathways.

CONCLUSIONS

PAH may arise when regulatory T-cell (Treg) activity fails to control endothelial injury. These studies suggest that regulatory T cells normally function to limit vascular injury and may protect against the development of PAH.

Regulatory T cells in lung transplantation--an emerging concept

Lung transplantation represents an option for patients with a variety of end-stage lung diseases. While surgical advances have led to improvements in short-term survival, long-term survival is limited by chronic rejection termed bronchiolitis obliterans syndrome (BOS). A growing body of work is devoted to determining why some patients develop BOS. One avenue of interest that has emerged recently is the role that regulatory T cells (Tregs) may have in protection from BOS. In this review, we will discuss the evidence that Tregs are relevant to outcomes following transplant. We will discuss the relevant animal models, in vitro assays, and human observational studies that support a role for Tregs. We will also explore the interplay between injurious T cells such as Th17 cells and Tregs as well as the effect that additional cell types and chemokines have on the balance between inflammation and regulation. Finally, we will review emerging therapies which may harness the ability of Tregs to lessen the effects of BOS.

Respiratory virus-induced dysregulation of T-regulatory cells leads to chronic rejection

BACKGROUND

Lower respiratory viral infections predispose to bronchiolitis obliterans syndrome (BOS). In addition, there is emerging evidence to support the role of autoimmunity in the pathogenesis of BOS. Because CD4(+)CD25(+)Foxp3(+) regulatory T-cells (Treg) control autoimmunity, we tested the hypothesis that respiratory virus-induced Treg dysfunction leads to BOS.

METHODS

Treg frequency was monitored using flow cytometry. Apoptosis, cytokines, and antibodies were analyzed using annexin V assay, LUMINEX, and enzyme-linked immunosorbent assay, respectively. Murine studies were performed using the orthotopic tracheal transplant model.

RESULTS

(A) Human studies: Treg troughs (decrease >50% of baseline) were found in 13 (43.3%) of 30 lung transplant recipients. Treg isolated during troughs revealed increased apoptosis (37.8%). Patients with Treg troughs had increased prevalence of antibodies to self-antigens collagen type I (23.1% vs 5.8% pretrough), collagen V (7.7% vs 0%), and k-alpha tubulin (30.7% vs 11.7%, p < 0.01) at 6 months post-trough. Increased number of Treg troughs correlated with more rapid onset of BOS. (B) Murine studies: Infection of tracheal transplant recipients with murine parainfleunza sendai virus led to increased Treg apoptosis (50.5%) in the draining lymph nodes. Vaccination against sendai virus prior to transplant abrogated apoptosis of Treg. In vitro, sendai virus-infected, but not naive, tracheal epithelial cells demonstrated upregulation of FasL (>3.5-fold) and induction of co-cultured Treg apoptosis (5.6-fold increase).

CONCLUSIONS

Respiratory viral infections cause Treg apoptosis which leads to the development of de novo autoimmunity that may play a role in the pathogenesis of BOS.

T cell activation leads to protein kinase C theta-dependent inhibition of TGF-beta signaling

TGF-beta is an ubiquitous cytokine that plays a pivotal role in the maintenance of self-tolerance and prevention of immunopathologies. Under steady-state conditions, TGF-beta keeps naive T cells in a resting state and inhibits Th1 and Th2 cell differentiation. Because rapid generation of Th1 and Th2 effector cells is needed in response to pathogen invasion, how do naive T cells escape from the quiescent state maintained by TGF-beta? We hypothesized that stimulation by strong TCR agonists might interfere with TGF-beta signaling. Using both primary mouse CD4(+) T cells and human Jurkat cells, we observed that strong TCR agonists swiftly suppress TGF-beta signaling. TCR engagement leads to a rapid increase in SMAD7 levels and decreased SMAD3 phosphorylation. We present evidence that TCR signaling hinders SMAD3 activation by inducing recruitment of TGF-betaRs in lipid rafts together with inhibitory SMAD7. This effect is dependent on protein kinase C, a downstream TCR signaling intermediary, as revealed by both pharmacological inhibition and expression of dominant-negative and constitutively active protein kinase C mutants. This work broadens our understanding of the cross-talk occurring between the TCR and TGF-beta signaling pathways and reveals that strong TCR agonists can release CD4 T cells from constitutive TGF-beta signaling. We propose that this process may be of vital importance upon confrontation with microbial pathogens.

Protection against bronchiolitis obliterans syndrome is associated with allograft CCR7+ CD45RA- T regulatory cells

Bronchiolitis obliterans syndrome (BOS) is the major obstacle to long-term survival after lung transplantation, yet markers for early detection and intervention are currently lacking. Given the role of regulatory T cells (Treg) in modulation of immunity, we hypothesized that frequencies of Treg in bronchoalveolar lavage fluid (BALF) after lung transplantation would predict subsequent development of BOS. Seventy BALF specimens obtained from 47 lung transplant recipients were analyzed for Treg lymphocyte subsets by flow cytometry, in parallel with ELISA measurements of chemokines. Allograft biopsy tissue was stained for chemokines of interest. Treg were essentially all CD45RA(-), and total Treg frequency did not correlate to BOS outcome. The majority of Treg were CCR4(+) and CD103(-) and neither of these subsets correlated to risk for BOS. In contrast, higher percentages of CCR7(+) Treg correlated to reduced risk of BOS. Additionally, the CCR7 ligand CCL21 correlated with CCR7(+) Treg frequency and inversely with BOS. Higher frequencies of CCR7(+) CD3(+)CD4(+)CD25(hi)Foxp3(+)CD45RA(-) lymphocytes in lung allografts is associated with protection against subsequent development of BOS, suggesting that this subset of putative Treg may down-modulate alloimmunity. CCL21 may be pivotal for the recruitment of this distinct subset to the lung allograft and thereby decrease the risk for chronic rejection.

Reflux-induced collagen type v sensitization: potential mediator of bronchiolitis obliterans syndrome

BACKGROUND

Lung transplantation continues to have poor long-term survival partly because of the high incidence of bronchiolitis obliterans syndrome (BOS). Gastroesophageal reflux disease (GERD) has been implicated in BOS pathogenesis. We investigated the role of collagen type V [col(V)] sensitization in this process.

METHODS

Only primary lung transplant recipients were included. Reflux status was assessed with pH monitoring, impedance plethysmography, and esophagogastroduodenoscopy. Sensitivity to col(V) was determined with trans vivo delayed-type hypersensitivity reaction (DTH). Kaplan-Meier analyses were performed.

RESULTS

Of the 54 recipients, 26 had proven GERD. There were no significant between-group differences in diagnosis; donor and recipient age; sex; ischemic time; single vs bilateral; human leukocyte antigen A, B, and DR matching cytomegalovirus status; acute rejections; or mean follow-up period. The mean DTH response in the GERD group was 25.7 x 10(-4) inches vs 18.3 x 10(-4) inches in the non-GERD group (P = .023). There was a significant reduction in BOS-free survival in the GERD group for both BOS-I (GERD+, 28.3%; GERD-, 86.6%; P = .0001) and BOS-II/III (GERD+, 66.2%; GERD-, 91.7%; P = .0374). A second cohort of 53 patients awaiting lung transplantation also was assayed. The mean DTH response in the GERD group was 24.0 x 10(-4) inches vs 13.1 x 10(-4) inches in the non-GERD group (P = .003). There were no differences in age or sex.

CONCLUSIONS

GERD is strongly associated with the development of BOS after primary lung transplantation. Col(V) sensitization is associated with reflux and BOS and may play an intermediary role in the pathogenesis of BOS. Trials using col(V) reactivity to assess the impact of antireflux procedures in patients with lung transplantation and idiopathic pulmonary fibrosis are warranted.

Smad7 in T cells drives T helper 1 responses in multiple sclerosis and experimental autoimmune encephalomyelitis

Autoreactive CD4+ T lymphocytes play a vital role in the pathogenesis of multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis. Since the discovery of T helper 17 cells, there is an ongoing debate whether T helper 1, T helper 17 or both subtypes of T lymphocytes are important for the initiation of autoimmune neuroinflammation. We examined peripheral blood CD4+ cells from patients with active and stable relapsing-remitting multiple sclerosis, and used mice with conditional deletion or over-expression of the transforming growth factor-beta inhibitor Smad7, to delineate the role of Smad7 in T cell differentiation and autoimmune neuroinflammation. We found that Smad7 is up-regulated in peripheral CD4+ cells from patients with multiple sclerosis during relapse but not remission, and that expression of Smad7 strongly correlates with T-bet, a transcription factor defining T helper 1 responses. Concordantly, mice with transgenic over-expression of Smad7 in T cells developed an enhanced disease course during experimental autoimmune encephalomyelitis, accompanied by elevated infiltration of inflammatory cells and T helper 1 responses in the central nervous system. On the contrary, mice with a T cell-specific deletion of Smad7 had reduced disease and central nervous system inflammation. Lack of Smad7 in T cells blunted T cell proliferation and T helper 1 responses in the periphery but left T helper 17 responses unaltered. Furthermore, frequencies of regulatory T cells were increased in the central nervous system of mice with a T cell-specific deletion and reduced in mice with a T cell-specific over-expression of Smad7. Downstream effects of transforming growth factor-beta on in vitro differentiation of naïve T cells to T helper 1, T helper 17 and regulatory T cell phenotypes were enhanced in T cells lacking Smad7. Finally, Smad7 was induced during T helper 1 differentiation and inhibited during T helper 17 differentiation. Taken together, the level of Smad7 in T cells determines T helper 1 polarization and regulates inflammatory cellular responses. Since a Smad7 deletion in T cells leads to immunosuppression, Smad7 may be a potential new therapeutic target in multiple sclerosis.

Transfer of tolerance to collagen type V suppresses T-helper-cell-17 lymphocyte-mediated acute lung transplant rejection

BACKGROUND

Rat lung allograft rejection is mediated by collagen type V (col(V)) specific T-helper-cell 17 (Th17) cells. Adoptive transfer of these cells is sufficient to induce rejection pathology in isografts, whereas tolerance to col(V) suppresses allograft rejection. Therefore, we tested whether regulatory T cells from tolerant rats could suppress the Th17-mediated rejection in the syngeneic model of lung transplantation.

METHODS

Rats were subjected to syngeneic left lung transplantation, and acute rejection was induced by adoptive transfer of lymph node cells from col(V)-immunized rats. Tolerance was induced by intravenous injection of col(V), and spleen lymphocytes were used for adoptive transfer. CD4+ T cells were depleted using magnetic beads. Lung isografts were analyzed using micro-positron emission tomography imaging and histochemistry. The transvivo delayed type hypersensitivity assay was used to analyze the Th17 response.

RESULTS

Adoptive cotransfer of col(V)-specific effector cells with cells from col(V)-tolerized rats suppressed severe vasculitis and bronchiolitis with parenchymal inflammation, and the expression of interleukin (IL)-17 transcripts in mediastinal lymph nodes induced by effector cells alone. Analysis by transvivo delayed type hypersensitivity showed that the reactivity to col(V) was dependent on the presence of tumor necrosis factor-alpha and IL-17 but not interferon-gamma. Depletion of CD4+ T cells from the suppressor cell population abrogated the col(V)-specific protection.

CONCLUSION

Th17-mediated acute rejection after lung transplantation is ameliorated by CD4+ col(V)-specific regulatory T cells. The mechanism for this Th17 suppression is consistent with tolerance induction to col(V). The goal of transplantation treatment, therefore, should target Th17 development and not suppression of T-cell activation by suppressing IL-2.

Collagen V-induced nasal tolerance downregulates pulmonary collagen mRNA gene and TGF-beta expression in experimental systemic sclerosis

Background

The purpose of this study was to evaluate collagen deposition, mRNA collagen synthesis and TGF-beta expression in the lung tissue in an experimental model of scleroderma after collagen V-induced nasal tolerance.

Methods

Female New Zealand rabbits (N = 12) were immunized with 1 mg/ml of collagen V in Freund's adjuvant (IM). After 150 days, six immunized animals were tolerated by nasal administration of collagen V (25 μg/day) (IM-TOL) daily for 60 days. The collagen content was determined by morphometry, and mRNA expressions of types I, III and V collagen were determined by Real-time PCR. The TGF-beta expression was evaluated by immunostaining and quantified by point counting methods. To statistic analysis ANOVA with Bonferroni test were employed for multiple comparison when appropriate and the level of significance was determined to be p < 0.05.

Results

IM-TOL, when compared to IM, showed significant reduction in total collagen content around the vessels (0.371 ± 0.118 vs. 0.874 ± 0.282, p < 0.001), bronchioles (0.294 ± 0.139 vs. 0.646 ± 0.172, p < 0.001) and in the septal interstitium (0.027 ± 0.014 vs. 0.067 ± 0.039, p = 0.026). The lung tissue of IM-TOL, when compared to IM, showed decreased immunostaining of types I, III and V collagen, reduced mRNA expression of types I (0.10 ± 0.07 vs. 1.0 ± 0.528, p = 0.002) and V (1.12 ± 0.42 vs. 4.74 ± 2.25, p = 0.009) collagen, in addition to decreased TGF-beta expression (p < 0.0001).

Conclusions

Collagen V-induced nasal tolerance in the experimental model of SSc regulated the pulmonary remodeling process, inhibiting collagen deposition and collagen I and V mRNA synthesis. Additionally, it decreased TGF-beta expression, suggesting a promising therapeutic option for scleroderma treatment.

Type V collagen-induced oral tolerance plus low-dose cyclosporine prevents rejection of MHC class I and II incompatible lung allografts

Autoimmunity to type V collagen (col(V)) is a major risk factor for lung allograft rejection. Although col(V)-induced oral tolerance abrogates rejection of minor histoincompatible lung transplants, its ability to prevent rejection of fully MHC incompatible lung allografts is unknown. Rat lung allografts fully incompatible at MHC class I and II loci (Brown Norway (RT1(n))) were transplanted into untreated Wistar Kyoto rat recipients (WKY, RT1(l)), or WKY rats were fed col(V) pretransplantation. To determine whether col(V) enhanced cyclosporine (CsA)-mediated immune suppression, WKY rats were treated with low-dose CsA (5 mg/kg), posttransplant, or oral col(V) plus CsA. The data showed that in contrast to col(V) or CsA, col(V) plus low-dose CsA significantly prevented rejection pathology, down-regulated alloantigen-induced production of IFN-gamma and IL-17A, and suppressed chemotaxis for lung macrophages in allograft bronchoalveolar lavage fluid that was associated with lower local levels of MCP-1 (CCL2). Col(V) plus CsA was associated with alloantigen-induced expression of IL-10 in mediastinal lymph node or splenic T cells, intragraft expression of IL-10 and Foxp3 in perivascular and peribronchiolar mononuclear cells, and constitutive production of IL-10 from allograft alveolar macrophages. These data demonstrate that col(V) enhances low-dose CsA-mediated immune suppression, and suggest a role for oral col(V) in immune modulation in lung transplantation.

Bronchiolitis obliterans in lung transplantation: the good, the bad, and the future

Lung transplantation remains the hope for many incurable pulmonary diseases, such as cystic fibrosis, pulmonary fibrosis, and chronic obstructive pulmonary disease. Remarkable progress has been made in improving outcomes, although the incidence of acute rejection remains more than 50% in the 1st year, and the 5-year graft survival is still less than 50% primarily because of the development of chronic rejection and graft dysfunction. Chronic rejection is characterized by the development of obliterative bronchiolitis in allografts and manifests as bronchiolitis obliterans syndrome in humans with no effective treatment. Previous studies support a role for alloreactive T cells in the development of bronchiolitis obliterans syndrome, but the specific mechanisms are unknown. One major stumbling block to research in the field of lung transplantation has been the lack of physiologic models to study the disease in the laboratory. We will review the current understanding of the immunology of the pathogenesis of obliterative bronchiolitis and will discuss exciting new advances from the laboratory as well as the implications for future research in lung transplantation.

Genotype-dependent tumor regression in Marek's disease mediated at the level of tumor immunity

Marek's disease (MD) of chickens is a unique natural model of Hodgkin's and Non Hodgkin's lymphomas in which the neoplastically-transformed cells over-express CD30 (CD30(hi)) antigen. All chicken genotypes can be infected with MD virus and develop microscopic lymphomas. From 21 days post infection (dpi) microscopic lymphomas regress in resistant chickens but, in contrast, they progress to gross lymphomas in susceptible chickens. Here we test our hypothesis that in resistant chickens at 21 dpi the tissue microenvironment is pro T-helper (Th)-1 and compatible with cytotoxic T lymphocyte (CTL) immunity but in susceptible lines it is pro Th-2 or pro T-regulatory (T-reg) and antagonistic to CTL immunity. We used the B2, non-MHC-associated, MD resistance/susceptibility system (line [L]6(1)/line [L]7(2)) and quantified the levels of key mRNAs that can be used to define Th-1 (IL-2, IL-12, IL-18, IFNgamma), Th-2 (IL-4, IL-10) and T-reg (TGFbeta, GPR-83, CTLA-4, SMAD-7) lymphocyte phenotypes. We measured gene expression in both whole tissues (represents tissue microenvironment and tumor microenvironment) and in the lymphoma lesions (tumor microenvironment) themselves. Gene ontology-based modeling of our results shows that the dominant phenotype in whole tissue as well as in microscopic lymphoma lesions, is pro T-reg in both L6(1) and L7(2) but a minor pro Th-1 and anti Th-2 tissue microenvironment exists in L6(1) whereas there is an anti Th-1 and pro Th-2 tissue microenvironment in L7(2). The tumor microenvironment per se is pro T-reg, anti Th-1 and pro Th-2 in both L6(1) and L7(2). Together our data suggests that the neoplastic transformation is essentially the same in both L6(1) and L7(2) and that resistance/susceptibility is mediated at the level of tumor immunity in the tissues.

The neoplastically transformed (CD30hi) Marek's disease lymphoma cell phenotype most closely resembles T-regulatory cells

INTRODUCTION

Marek's disease (MD), a herpesvirus-induced lymphoma of chickens is a unique natural model of CD30-overexpressing (CD30hi) lymphoma. We have previously proposed that the CD30hi neoplastically transformed CD4+ T cells in MD lymphomas have a phenotype antagonistic to cell mediated immunity. Here were test the hypothesis that the CD30hi neoplastically transformed MD lymphoma cells have a phenotype more closely resembling T-helper (Th)-2 or regulatory T (T-reg) cells.

MATERIALS AND METHODS

We separated ex vivo-derived CD30hi, from the CD30lo/- (non-transformed), MD lymphoma cells and then quantified the relative amounts of mRNA and proteins for cytokines and other genes that define CD4+ Th-1, Th-2 or T-reg phenotypes.

RESULTS AND DISCUSSION

Gene Ontology-based modeling of our data shows that the CD30hi MD lymphoma cells having a phenotype more similar to T-reg. Sequences that could be bound by the MD virus putative oncoprotein Meq in each of these genes' promoters suggests that the MD herpesvirus may play a direct role in maintaining this T-reg-like phenotype.

TGF-beta inhibits IL-2 production and promotes cell cycle arrest in TCR-activated effector/memory T cells in the presence of sustained TCR signal transduction

TGF-beta signaling is critical for controlling naive T cell homeostasis and differentiation; however, the biological and biochemical changes induced by TGF-beta in effector/memory T cells are poorly defined. We show that although TGF-beta inhibits effector/memory peripheral blood T lymphoblast proliferation and IL-2 production, the intensity and kinetics for TCR-induced global tyrosine phosphorylation are markedly increased compared with that in untreated cells or naive T cells. After TCR ligation, tyrosine phosphorylation of proximal tyrosine kinases and docking proteins like linker for activation of T cells is maintained for >30 min in TGF-beta-primed cells compared with untreated cells where phosphorylation of these targets returned to basal levels by 10 min. Extended phosphorylation of linker for activation of T cells in treated peripheral blood T selectively prolongs ERK 1/2 signaling and phospholipase C-gamma1 activation leading to increased Ca(2+) flux. A kinase/phosphatase imbalance could not account for extended phosphorylation as CD45R, SHP-1, and SHP-2 expression remains unaltered. The contradiction between prolonged signal transduction and inhibition of proliferation is partially explained by the observation that TGF-beta priming results in ERK 1/2-independent p21 induction and decreased cyclin D1 expression leading to accumulation of T cells in G(0)/G(1) phases of the cell cycle and cell cycle arrest. Despite inhibition of T cell function by TGF-beta priming, TCR and cytokine signaling pathways are intact and selectively extended, suggesting that suppression in the effector/memory T cell is mediated by reprogramming signal transduction, rather than its inhibition as in the naive T cell.

Animal models for bronchiolitis obliterans syndrome following human lung transplantation

Lung transplantation is the only viable treatment option that can improve survival and enhance the quality of life of patients with end-stage lung diseases such as emphysema, cystic fibrosis, idiopathic pulmonary fibrosis, and primary pulmonary hypertension. However, the long-term survival of lung allografts is still limited by the development of bronchiolitis obliterans syndrome (BOS), an irreversible condition unresponsive to therapy. BOS is the most significant cause of long-term morbidity and mortality after lung transplantation. Over the past decade, several animal models have been developed to investigate BOS. These are valuable to elucidate the immunologic and pathologic mechanisms that lead to BOS and to test treatment options for BOS. In this review, we discuss the advantages and disadvantages of different animal models and highlight work that has been done with each model.

Silencing S1P1 receptors regulates collagen-V reactive lymphocyte-mediated immunobiology in the transplanted lung

Type V collagen (col[V])-reactive lymphocytes contribute to lung transplant rejection, but the mechanisms for emigration into the graft are unknown. Sphingosine-1-phosphate-1 receptors (S1P(1R)) are believed to be required for lymphocyte emigration in other studies, but their role in col(V)-reactive lymphocyte rejection responses is not known. Utilizing small interfering RNA (siRNA) to reduce S1P(1R) expression on col(V)-reactive lymphocytes, we examined the role of S1P(1R) in the rejection response. Quantitative polymerase chain reaction (PCR) revealed strong expression of S1P(1R) messenger RNA (mRNA)on col(V)-reactive lymphocytes isolated from immunized rats. S1P(1R)-specific siRNA (S1P(1R) siRNA) reduced expression of S1P(1R) mRNA and protein, whereas scramble siRNA (SC siRNA) had no effect. Adoptive transfer of lymphocytes treated with S1P(1R) siRNA to rat Wistar Kyoto (WKY) lung isograft recipients resulted in retention of cells within the liver with fewer cells in mediastinal lymph nodes when compared to cells exposed to SC siRNA. S1P(1R)-deficient cells proliferated in response to alloantigens, but not in response to col(V), and produced less interferon (IFN)-gamma in response to col(V) compared to controls. Downregulating S1P(1R) did not affect production of interleukin (IL)-10and tumor necrosis factor (TNF)-alpha, or expression of adhesion molecules critical for migration, but prevented rejection pathology and lowered local levels of IFN-gamma post adoptive transfer. These data demonstrate novel roles of S1P(1R,) which include regulating emigration and modulating lymphocyte activation.

Th-17, monokines, collagen type V, and primary graft dysfunction in lung transplantation

RATIONALE

The pathogenesis of primary graft dysfunction (PGD), a serious complication of lung transplantation, is poorly understood. Human studies and rodent models have shown that collagen type V (col[V]), stimulates IL-17-dependent cellular immunity after lung transplantation.

OBJECTIVES

To determine whether patients with end-stage lung disease develop pretransplant col(V)-specific cellular immunity, and if so, the impact of this response on PGD.

METHODS

Trans-vivo delayed-type hypersensitivity (TV-DTH) assays were used to evaluate memory T-cell responses to col(V) in 55 patients awaiting lung transplantation. Pa(O(2))/Fi(O(2)) index data were used to assess PGD. Univariate risk factor analysis was performed to identify variables associated with PGD. Rats immunized with col(V) or irrelevant antigen underwent lung isografting to determine if prior anti-col(V) immunity triggers PGD in the absence of alloreactivity.

MEASUREMENTS AND MAIN RESULTS

We found that 58.8% (10/17) of patients with idiopathic pulmonary fibrosis, and 15.8% (6/38) of patients without idiopathic pulmonary fibrosis tested while on the wait list for a lung transplant were col(V) DTH positive. Col(V) reactivity was CD4(+) T-cell and monocyte mediated, and dependent on IL-17, IL-1beta, and tumor necrosis factor (TNF)-alpha. Pa(O(2))/Fi(O(2)) indices were impaired significantly 6-72 hours after transplantation in col(V)-reactive versus nonreactive patients. Univariate risk factor analysis identified only preoperative TV-DTH to col(V) and ischemic time as predictors of PGD. Finally, in a rat lung isograft model, col(V) sensitization resulted in significantly lower Pa(O(2))/Fi(O(2)), increased local TNF-alpha and IL-1beta production, and a moderate-to-severe bronchiolitis/vasculitis when compared with control isografts.

CONCLUSIONS

The data suggest that activation of innate immunity by col(V)-specific Th-17 memory cells represents a novel pathway to PGD after lung transplantation.

Cutting edge: trans-signaling via the soluble IL-6R abrogates the induction of FoxP3 in naive CD4+CD25 T cells

Chronic inflammatory diseases may develop when regulatory T cells (Tregs) fail to control the balance between tolerance and immunity. Alternatively, activated immune cells might prevent the induction or activation of Tregs in such diseases. In this study, we demonstrate that trans-signaling into T cells via the soluble IL-6 receptor completely abrogates the de novo induction of adaptive Tregs. Mechanistically, IL-6 trans-signaling augmented the expression of the TGF-beta signaling inhibitor SMAD7. Consequently, SMAD7 overexpression in T cells using newly created transgenic mice rendered CD4(+)CD25(-) T cells resistant to the induction of FoxP3. Finally, IL-6 trans-signaling inhibited Treg-mediated suppression in a murine model of colitis. In summary, IL-6 trans-signaling into T cells emerges as a key pathway for blockade of the development of adaptive Tregs and thus may play a pivotal role in shifting the balance between effector and regulatory T cell numbers in chronic inflammatory and autoimmune diseases.

Lung Transplantation in the Fischer 344→Wistar Kyoto Rat Strain Combination is Not Suitable to Study Bronchiolitis Obliterans

BACKGROUND

To elucidate the pathogenesis of bronchiolitis obliterans (BO) a reliable animal model is needed. According to the literature, lung transplantation from Fischer 344 (F344) to Wistar Kyoto (WKY) rats is the only model that reliably results in BO without a further stimulus.

METHODS

We performed orthotopic left lung transplantation in F344 to WKY rats and in both isogeneic rat strain combinations. Suture and cuff techniques for anastomosis were compared. The time course of rejection and the morphology of the bronchial anastomoses were documented by repeated flat-panel volumetric computed tomography (fpVCT) in the living animal. Graft histopathology was analyzed 3 months post-transplant.

RESULTS

According to the graft outcome, as revealed by fpVCT, grafts were sub-divided into two groups: In Group 1, infiltrates due to acute rejection occurred early after transplantation and resolved thereafter. Graft histopathology showed minor changes but no BO. In Group 2, acute rejection caused total atelectasis that never resolved. After 3 months, grafts were shrunken and exhibited tissue remodeling with some similarities to BO. No correlation between graft outcome and anastomotic technique was apparent.

CONCLUSIONS

Modeling lung transplantation using the F344-to-WKY combination is without clinical relevance because BO does not develop in grafts with life-sustaining function. Consecutive fpVCT is useful to monitor pathologic changes in rat pulmonary grafts.

Metalloproteinase Inhibition Has Differential Effects on Alloimmunity, Autoimmunity, and Histopathology in the Transplanted Lung

BACKGROUND

Upregulation of matrix metalloproteinases (MMPs) has been associated with chronic lung allograft rejection known as bronchiolitis obliterans syndrome. It has been suggested that MMP inhibition could prevent the rejection response. However, the effect of MMP inhibition on lung allograft rejection has not been reported.

METHODS

Utilizing a rat model of lung transplantation, tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) were overexpressed by gene therapy in F344 rat lung allografts prior to transplantation into WKY recipient rats. Separately, WKY rats that received F344 lung allografts were treated systemically with COL-3, a global MMP inhibitor.

RESULTS

TIMP-1 and TIMP-2 had differential effects on delayed type hypersensitivity (DTH) responses to donor antigens and type V collagen, an autoantigen involved in the rejection response. Neither TIMP-1 or TIMP-2 affected the onset of rejection pathology. COL-3 suppressed DTH responses to donor antigens and type V collagen, abrogated local production of tumor necrosis factor-alpha, and interleukin-1beta. Although it did not prevent rejection pathology, COL-3 (30 mg/kg) induced intragraft B cell hyperplasia suggestive of posttransplant proliferative disorder (PTLD).

CONCLUSIONS

These data identify a complex role for MMPs and TIMPs in the immunopathogenesis of lung allograft rejection, and indicate their effects are not limited to matrix remodeling.

Pin1 modulates the type 1 immune response

Background/Abstract

Immune responses initiated by T cell receptor (TCR) and costimulatory molecule mediated signaling culminate in maximal cytokine mRNA production and stability. The transcriptional responses to co-stimulatory T cell signalling involve calcineurin and NF-AT, which can be antagonized by interference with the cis-trans peptidyl-prolyl isomerases (PPIase), cyclophilin A and FKBP. Signalling molecules downstream of CD28 which are essential for the stabilization of cytokine mRNAs are largely unknown.

Methodology/Principal Findings

We now show that Pin1, a third member of the PPIase family mediates the post-transcriptional regulation of Th1 cytokines by activated T cells. Blockade of Pin1 by pharmacologic or genetic means greatly attenuated IFN-γ, IL-2 and CXCL-10 mRNA stability, accumulation and protein expression after cell activation. In vivo, Pin1 blockade prevented both the acute and chronic rejection of MHC mismatched, orthotopic rat lung transplants by reducing the expression of IFN-γ and CXCL-10. Combined transcriptional and post-transcriptional blockade with cyclosporine A and the Pin1 inhibitor, juglone, was synergistic.

Conclusions/Significance

These data suggest Pin1 inhibitors should be explored for use as immunosuppressants and employed with available calcineurin inhibitors to reduce toxicity and enhance effectiveness.

CD25+ CD4+ regulatory T-cells in cancer

Regulatory T-cells (Treg) protect the host from autoimmune disease by suppressing self-reactive immune cells. As such, Treg may also block antitumor immune responses. Recent observations by us and others showed that the prevalence of Treg is increased in cancer patients, particularly in the tumor environment. Our studies in a mouse pancreas cancer model suggest that the tumor actively promotes the accrual of Treg through several mechanisms involving activation of naturally occurring Treg as well as conversion of non-Treg into Treg. Our studies focus on further defining these mechanisms with the ultimate goal of designing strategies that block Treg-mediated suppression in cancer patients.

TGF-beta inhibition of CTL re-stimulation requires accessory cells and induces peroxisome-proliferator-activated receptor-gamma (PPAR-gamma)

Effective cellular immunity to Epstein-Barr virus (EBV), necessary to prevent or cure many post-transplant lymphoproliferative disorders (PTLD), can be inhibited by transforming growth factor-beta (TGF-beta). In vitro, TGF-beta inhibits memory CTL re-stimulation from whole PBMC. We show that the effect of TGF-beta on CTL re-stimulation is not directly on the T cell, but requires an accessory cell (AC) population. Further, pre-treatment of AC with TGF-beta significantly reduces memory CTL re-stimulation and suppresses delayed type hypersensitivity (DTH) responses. Addition of exogenous interferon-gamma to the AC overcomes the effects of TGF-beta. TGF-beta pre-treatment also up-regulates expression of peroxisome-proliferator-activated receptor-gamma (PPAR-gamma) in CD14(+) AC. Importantly, pre-treatment of AC with the PPAR-gamma ligand, ciglitazone, results in significantly reduced memory CTL re-stimulation. Thus, the effects of TGF-beta in this system may be mediated in part via PPAR-gamma, and PPAR-gamma activation could have significant inhibitory effects on memory T-cell responses by affecting AC function. These data have important implications in understanding how memory CTL are re-stimulated and function to prevent disease, especially PTLD.

Regulatory T cell-mediated transplantation tolerance

The existence of naturally occurring regulatory T cells in normal hosts and their pivotal role in maintaining both auto- and allo-tolerance have direct implications on the therapy of autoimmune disorders and for achieving immunosuppression-free allotransplantation. Among the various forms of regulatory T cells described, CD4(+)CD25(+) T cells have emerged as one of the most potent tolerogenic subsets. In this review, we discuss the molecular basis of development and function of these regulatory T cells and their potential role in the context of chronic lung allograft rejection.

Anti-type V collagen lymphocytes that express IL-17 and IL-23 induce rejection pathology in fresh and well-healed lung transplants

Immunity to collagen V [col(V)] contributes to lung 'rejection.' We hypothesized that ischemia reperfusion injury (IRI) associated with lung transplantation unmasks antigenic col(V) such that fresh and well-healed lung grafts have differential susceptibility to anti-col(V)-mediated injury; and expression of the autoimmune cytokines, IL-17 and IL-23, are associated with this process. Adoptive transfer of col(V)-reactive lymphocytes to WKY rats induced grade 2 rejection in fresh isografts, but induced worse pathology (grade 3) when transferred to isograft recipients 30 days post-transplantation. Immunhistochemistry detected col(V) in fresh and well-healed isografts but not native lungs. Hen egg lysozyme-reactive lymphocytes (HEL, control) did not induce lung disease in any group. Col(V), but not HEL, immunization induced transcripts for IL-17 and IL-23 (p19) in the cells utilized for adoptive transfer. Transcripts for IL-17 were upregulated in fresh, but not well-healed isografts after transfer of col(V)-reactive cells. These data show that IRI predisposes to anti-col(V)-mediated pathology; col(V)-reactive lymphocytes express IL-17 and IL-23; and anti-col(V)-mediated lung disease is associated with local expression of IL-17. Finally, because of similar histologic patterns, the pathology of clinical rejection may reflect the activity of autoimmunity to col(V) and/or alloimmunity.

Pulmonary immunity to viral infection: adenovirus infection of lung dendritic cells renders T cells nonresponsive to interleukin-2

Adenovirus (Ad) infection has been identified as predisposing hosts to the development of pulmonary disease through unknown mechanisms. Lung dendritic cells (DCs) are vital for initiating pulmonary immune responses; however, the effects of Ad infection on primary lung DC have not been studied. In contrast to the effects on bone marrow- and monocyte-derived DCs, the current study shows that Ad infection of murine BALB/c lung DCs in vitro and in vivo suppresses DC-induced T-cell proliferation. The effect of Ad on DCs was not due to a downregulation of major histocompatibility complex or costimulatory molecules. Analysis of the production of interleukin-12 (IL-12), alpha interferon (IFN-alpha), and IFN-gamma by the Ad-infected DCs shows no significant differences over noninfected control lung DCs. Ad-induced suppression was not due to a deficiency of IL-2 or other DC-secreted factors and was dependent on viral protein synthesis, as UV irradiation of Ad abrogated the suppressive effect. Results suggest that Ad-infected DCs induce T cells to be nonresponsive to IL-2 during primary coculture, as the addition of IL-2 in secondary cultures recovered T-cell proliferation. In vivo studies supported in vitro results showing that Ad infection resulted in lung T cells with decreased proliferative ability. This study demonstrates that Ad infection induces local immunoincompetence by altering DC-T-cell interactions.

Prolonged activation of virus-specific CD8+T cells after acute B19 infection

BACKGROUND

Human parvovirus B19 (B19) is a ubiquitous and clinically significant pathogen, causing erythema infectiosum, arthropathy, transient aplastic crisis, and intrauterine fetal death. The phenotype of CD8+ T cells in acute B19 infection has not been studied previously.

METHODS AND FINDINGS

The number and phenotype of B19-specific CD8+ T cell responses during and after acute adult infection was studied using HLA-peptide multimeric complexes. Surprisingly, these responses increased in magnitude over the first year post-infection despite resolution of clinical symptoms and control of viraemia, with T cell populations specific for individual epitopes comprising up to 4% of CD8+ T cells. B19-specific T cells developed and maintained an activated CD38+ phenotype, with strong expression of perforin and CD57 and downregulation of CD28 and CD27. These cells possessed strong effector function and intact proliferative capacity. Individuals tested many years after infection exhibited lower frequencies of B19-specific cytotoxic T lymphocytes, typically 0.05%-0.5% of CD8+ T cells, which were perforin, CD38, and CCR7 low.

CONCLUSION

This is the first example to our knowledge of an "acute" human viral infection inducing a persistent activated CD8+ T cell response. The likely explanation--analogous to that for cytomegalovirus infection--is that this persistent response is due to low-level antigen exposure. CD8+ T cells may contribute to the long-term control of this significant pathogen and should be considered during vaccine development.

Lung transplantation: opportunities for research and clinical advancement

Lung transplantation is the only definitive therapy for many forms of end-stage lung diseases. However, the success of lung transplantation is limited by many factors: (1) Too few lungs available for transplantation due to limited donors or injury to the donor lung; (2) current methods of preservation of excised lungs do not allow extended periods of time between procurement and implantation; (3) acute graft failure is more common with lungs than other solid organs, thus contributing to poorer short-term survival after lung transplant compared with that for recipients of other organs; (4) lung transplant recipients are particularly vulnerable to pulmonary infections; and (5) chronic allograft dysfunction, manifest by bronchiolitis obliterans syndrome, is frequent and limits long-term survival. Scientific advances may provide significant improvements in the outcome of lung transplantation. The National Heart, Lung, and Blood Institute convened a working group of investigators on June 14-15, 2004, in Bethesda, Maryland, to identify opportunities for scientific advancement in lung transplantation, including basic and clinical research. This workshop provides a framework to identify critical issues related to clinical lung transplantation, and to delineate important areas for productive scientific investigation.

Smad7 in TGF-beta-mediated negative regulation of gut inflammation

Mice with targeted disruptions of the transforming growth factor-beta1 (TGF-beta1) gene or TGF-beta1 intracellular signalling pathways develop intestinal inflammation. Conversely, TGF-beta1-producing regulatory T cells protect against experimental colitis. Paradoxically, however, TGF-beta1 production is high in the gut of patients with chronic inflammatory intestinal disease, and yet inflammation proceeds unchecked. Here we discuss the functional role of Smad7, an intracellular inhibitor of TGF-beta1 signalling, in the control of gut inflammation by TGF-beta1. In particular, we delineate a scenario in which the high expression of Smad7 in inflammatory cells renders them unresponsive to TGF-beta1 and propose that control of Smad7, not TGF-beta1 production, is a key determinant in understanding how TGF-beta1 negatively regulates gut inflammation.

The effects of pretreatment with donor antigen and immunosuppressive agents on fully allogenic tracheal graft

BACKGROUND

Obliterative bronchiolitis is a major clinical problem in cases involving a transplanted lung. We examined drug-induced tolerance to a fully allogenic tracheal graft in a murine heterotopic transplantation model.

MATERIALS AND METHODS

Recipient mice (C57BL/6) were primed iv with 1 x 10(8) splenocytes of donor mice (BALB/c). Day 0 was the day of the splenocyte injection. Cyclophosphamide and Busulfan were injected intraperitoneally on day 2. On day 3, 1 x 10(7) donor bone marrow cells were intravenously injected. On day 28, a donor tracheal graft was implanted into a subcutaneous pocket. Grafts were harvested at 3-week intervals, and the degree of obstruction of the inner cavity, the condition of epithelium, and the viability of chondrocytes were examined.

RESULTS

All of the isograft controls (BALB/c) and grafts implanted in the T cell-free recipients (BALB/c-nu) showed patent, lined epithelium and viable chondrocytes. All allografts tested showed total luminal occlusion by granulative tissue and inflammatory cells, and the epithelium was totally absent. Five of 11 drug-treated grafts were completely patent, although the epithelium was almost absent and the chondrocytes were substantially destroyed. However, when the chimerism was analyzed by flow cytometry analysis of the recipient T cells, approximately 90% of the donor cells were recognized.

CONCLUSIONS

Even by this pre-treatment-induced chimerism, a transplanted allogenic trachea was not completely preserved. The present results suggest that a non-allogenic response might have contributed to the rejection.