Inhibition of allogeneic T-cell response by Kupffer cells expressing indoleamine 2,3-dioxygenase

AIM:To explore the possibility and mechanism of inhibiting allogeneic T-cell responses by Kupffer cells (KC)pretreated with interferon-γ(IFN-γ)in vitro. METHODS:The expressions of indoleamine 2,3-dioxygenase(IDO)mRNA and FasL mRNA in KC pretreated with IFN-γwere studied with real-time polymerase chain reaction(PCR).The catabolism of tryptophan by IDO from KC was analyzed by high performance liquid chromatography.Allogeneic T-cell response was used to confirm the inhibition of KC in vitro.The proliferation o...     

吲哚胺2,3-二氧化酶对HepG2细胞生物学行为影响的研究

吲哚胺2,3-二氧化酶(indoleamine 2,3-dioxygenase,IDO)是细胞内一种含亚铁血红素的酶,是肝脏以外惟一可催化色氨酸分子中吲哚环氧化裂解,从而沿犬尿酸途径进行分解代谢的限速酶,可将色氨酸分解为L-犬尿酸、吡啶甲酸和喹啉酸等多种代谢物.     

Donor liver natural killer cells alleviate liver allograft acute rejection in rats

BACKGROUND:Liver enriched natural killer (NK) cells are of high immune activity.However,the function of donor liver NK cells in allogeneic liver transplantation (LTx) remains unclear.METHODS:Ten Gy of whole body gamma-irradiation (WBI) from a 60 Co source at 0.6 Gy/min was used for depleting donorderived leukocytes,and transfusion of purified liver NK cells isolated from the same type rat as donor (donor type liver NK cells,dtl NKs) through portal vein was performed immediately after grafting the irradiated...     

Liver allograft radiotherapy to treat rejection in children: efficacy in orthotopic liver transplantation and long-term safety.

BACKGROUND: We studied, retrospectively, the efficacy to control rejection and long-term safety of liver allograft radiotherapy (RT) performed in 14 children. Long-term safety data were collected with the prospect of possible use of RT in liver cell transplantation (LCT). METHODS: Immune suppression included cyclosporine, azathioprine and prednisone. In case of intractable rejection, low-dose allograft RT was administered daily for 3 days, and short-term efficacy was evaluated by liver enzyme assays and histology. The long-term outcome was compared with that of 122 patients undergone transplantation and who had similar treatment, but no RT. RESULTS: Survival at 15 years was 71.4% vs 69.7% in the comparison group. In the RT group, rejection control was complete in six of 14 children and partial in two, all being alive and well 14-18 years later. Ten of 14 children had follow-up biopsy. Six children had normal histology and four had mild unspecific fibrosis. The long-term follow-up biopsy in the comparison group showed fibrosis in 42 of 85 children. The incidence of complications was similar in both groups. CONCLUSIONS: This series shows that, such a RT regimen appeared to be efficient and safe as a rescue treatment for acute rejection. Provided that further investigations in animal models show a certain benefit of low-dose irradiation around LCT, such a regimen could be proposed in human liver cell transplant programmes.     

Serum markers of immune activation and liver allograft rejection

We monitored the immune response after liver transplantation in 20 patients by measuring the serum levels of soluble interleukin-2 receptor (sIL-2R), soluble CD8 (sCD8), serum amyloid-A protein (SAA), and tumor necrosis factor- (TNF-). In six patients data were available to extend the follow-up period to one year. In all patients mean sIL-2R levels increased in the first month after liver transplantation, and subsequently decreased to values similar to pre-OLT ones, while SAA mean levels rose in the first week after OLT only in patients with rejection. sCD8 levels did not significantly rise after OLT, and TNF- was undetectable in most cases. During episodes of rejection, rejector patients had significantly higher levels of sIL-2R, sCD8, and SAA than stable (without complications) patients. Conversely, no significant difference between rejectors and patients with other complications existed for any of the markers studied. These results diminish the importance of these serum markers of immune activation as laboratory tools in the differential diagnosis of acute rejection from other complications. However, sIL-2R, SAA, and sCD8 levels correlated with the histological grade of rejection and therefore can be utilized to monitor patients with an established diagnosis of acute rejection.     

Vitamin D and the risk of acute allograft rejection following human liver transplantation

Background: Vitamin D may act as an immune modulator in experimental and human organ transplantation, but these data are yet to be confirmed in human liver transplantation (LT). Aim: This study aimed to assess the relationship between acute liver allograft cellular rejection (ACR) and pretransplant serum vitamin D concentration or post‐transplant vitamin D supplementation. Method: We studied 133 LT recipients who underwent two per protocol allograft biopsies in the early post‐operative period, plus on‐demand biopsies as clinically indicated. ACR estimate was given according to the Banff scheme in biopsies obtained along two follow‐up periods: (a) from the transplant operation to the end of the second month (0–2 months); (b) and from the third month to the end of the eighth month (3–8 months) post‐LT. Results: The median pretransplant serum 25‐hydroxyvitamin D concentration was 12.5 ng/ml; 40 patients had concentrations ≤12.5 ng/ml, of whom six had ≤5.0 ng/ml. Seventy‐nine recipients received oral vitamin D₃ supplementation to treat post‐transplant osteoporosis. In the 0–2 months period, moderate‐to‐severe rejection episodes were independently associated with cytomegalovirus reactivation (P<0.005) and progressively lower pretransplant serum 25‐hydroxyvitamin D concentrations (P<0.02). Early vitamin D₃ supplementation was independently associated with a lack of ACR (P<0.05). Conclusions: These results suggest that vitamin D may favour immune tolerance towards the liver allograft.     

Expression of CD44 in rat liver allografts during rejection

As CD44 is believed to be a homing receptor involved in lymphoid trafficking and inflammatory responses, it is expected to be closely linked to transplant rejection. In this study, the expression of CD44 during liver transplant rejection was compared with the expression of lymphocyte-function associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1), which play an essential role in cell interactions and the initiation of immune responses. Male Brown Norway (BN) and Lewis (LEW) rats were used as donors and recipients, respectively. Orthotopic liver transplantation (OLTX) was done using the cuff technique of Kamada and Calne. Animals were killed on days 3, 5, and 7 after OLTX, and a piece of tissue from each of the liver grafts was obtained. Immunohistochemical staining was used to investigate the expression of CD44, ICAM-1, and LFA-1. CD44 was strongly expressed in portal areas of the rejected liver, and LFA-1 and ICAM-1 were expressed mainly on sinusoids and hepatocytes. These findings indicate that CD44 is closely involved in lymphocyte infiltration, which is dominant in portal areas, and that lymphocyte infiltration during the rejection process may involve a homing mechanism.     

Inhibition of indoleamine 2,3-dioxygenase augments trinitrobenzene sulfonic acid colitis in mice

BACKGROUND & AIMS: Indoleamine 2,3-dioxygenase (IDO), an interferon gamma-induced intracellular enzyme, inhibits lymphocyte proliferation through tryptophan degradation. IDO is highly expressed in the mammalian intestine. We sought to determine whether IDO played a regulatory role in the T-cell helper 1 (Th1)-mediated trinitrobenzene sulfonic acid (TNBS) model of colitis. METHODS: Intrarectal TNBS was given to SJL/J mice along with either placebo or a specific IDO inhibitor. IDO protein and mRNA expression were assessed by Western blotting and real-time PCR. Colonic lamina propria mononuclear cells (LPMNCs) were isolated, fractionated, and cultured, in the presence and absence of IFN-gamma, to determine the cell type(s) expressing IDO. RESULTS: IDO is expressed by professional antigen-presenting cells in the lamina propria. Induction of TNBS colitis resulted in a significant increase in IDO mRNA (P = 0.005) and protein expression. IDO inhibition during TNBS colitis resulted in an 80% mortality compared with 10% for placebo-treated animals (P = 0.0089). IDO inhibition resulted in a more severe colitis both histologically and morphologically (P < 0.05) and significantly increased colonic proinflammatory cytokine expression compared with placebo-treated animals. CONCLUSIONS: IDO is expressed in the normal colon and is up-regulated in the setting of TNBS colitis. Inhibition of IDO during TNBS colitis resulted in increased mortality and an augmentation of the normal inflammatory response. These findings suggest that IDO plays an important role in the down-regulation of Th1 responses within the gastrointestinal tract.     

Possible role of cytokine-induced tryptophan degradation in anaemia of inflammation

Anaemia of inflammation (AI) is a frequent complication in patients suffering from chronic inflammatory disorders including infections, autoimmune and malignant disease. Cytokine imbalance with a shift towards T-helper (Th)1-type immune response seems to be important in the pathogenesis of this type of anaemia. Interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha may affect the growth and differentiation of erythroid progenitor cells. In macrophages, IFN-gamma strongly induces indoleamine (2,3)-dioxygenase, an enzyme which degrades tryptophan (trp) to kynurenine (kyn). Trp availability is rate limiting for protein biosynthesis and thus cell growth, including erythropoiesis. In this study, trp and kyn concentrations and their relationship to haemoglobin concentrations and to immune activation was examined in 22 patients with AI. Patients with AI presented with lower trp concentrations than healthy controls of similar age, and a significantly higher kyn to trp ratio, suggesting enhanced trp degradation and, because of a positive correlation with neopterin, immune activation. The kyn to trp ratio was inversely correlated to haemoglobin levels. Thus, the limitation of trp availability to erythroid progenitors may be a key mechanism in cytokine-mediated inhibition of erythropoiesis, and the therapeutic modulation of indoleamine (2,3)-dioxygenase and trp levels may be promising targets for AI therapy.     

Prognostic value of indoleamine 2,3 dioxygenase in patients with higher-risk myelodysplastic syndromes treated with azacytidine

Hypomethylating agents (HMAs) are widely used in patients with higher-risk myelodysplastic syndromes (MDS) not eligible for stem cell transplantation; however, the response rate is <50%. Reliable predictors of response are still missing, and it is a major challenge to develop new treatment strategies. One current approach is the combination of azacytidine (AZA) with checkpoint inhibitors; however, the potential benefit of targeting the immunomodulator indoleamine-2,3-dioxygenase (IDO-1) has not yet been evaluated. We observed moderate to strong IDO-1 expression in 37% of patients with high-risk MDS. IDO-1 positivity was predictive of treatment failure and shorter overall survival. Moreover, IDO-1 positivity correlated inversely with the number of infiltrating CD8⁺ T cells, and IDO-1+ patients failed to show an increase in CD8⁺ T cells under AZA treatment. In vitro experiments confirmed tryptophan catabolism and depletion of CD8⁺ T cells in IDO-1+ MDS, suggesting that IDO-1 expression induces an immunosuppressive microenvironment in MDS, thereby leading to treatment failure under AZA treatment. In conclusion, IDO-1 is expressed in more than one-third of patients with higher-risk MDS, and is predictive of treatment failure and shorter overall survival. Therefore, IDO-1 is emerging as a promising predictor and therapeutic target, especially for combination therapies with HMAs or checkpoint inhibitors.     

吲哚胺-2,3双加氧酶在支气管哮喘和过敏症中的作用

变态反应(过敏症)是指机体对某些抗原初次应答后,再次接触相同抗原刺激时,产生以机体生理功能紊乱或组织损伤为主的一种特异性免疫应答.吲哚胺-2,3双加氧酶(indoleamine 2,3 dioxygenase,IDO)既是细胞内催化色氨酸分子沿犬尿酸途径进行分解代谢的限速酶,也是一种重要的免疫调节酶.越来越多的研究表明,免疫耐受机制缺陷在变应性疾病中扮演着重要的角色,而抗原递呈细胞(APC)如树突状细胞(DC)表达的IDO可通过多种机制诱导机体产生免疫耐受.因此,通过增加DC表达IDO而诱导免疫耐受,有望成为治疗支气管哮喘、变应性鼻炎和特应性皮炎的新靶点.     

Acute allograft rejection: cellular and humoral processes

Acute cellular rejection affects greater than one-third of lung transplant recipients. Alloreactive T-lymphocytes constitute the basis of lung allograft rejection. Recent evidence supports a more complex immune response to the allograft. Interaction between recipient genetics, immunosuppression therapies, and allograft environmental exposures likely contribute to high rejection rates after lung transplantation. A greater understanding of the heterogeneous mechanisms of lung rejection is critical to developing effective therapies that target the precise pathophysiology of the disease and ultimately improve long-term lung transplant outcomes.     

Late-onset acute rejection after living donor liver transplantation

INTRODUCTION Standard regimens for immunosuppressive therapy after liver transplantation include calcineurin inhibitors and steroids, which result in a reduced incidence of acute rejection and improved recipient survival[1]. The long- term complications o…     

Decreased indoleamine 2,3-dioxygenase expression in dendritic cells and role of indoleamine 2,3-dioxygenase-expressing dendritic cells in immune thrombocytopenia

Indoleamine 2,3-dioxygenase (IDO) expression in dendritic cells (DCs) can induce or maintain peripheral immune tolerance. Impaired IDO-mediated tryptophan catabolism has been observed in autoimmune diseases. In order to investigate the effects of IDO-mediated tryptophan catabolism and IDO-expressing DCs in immune thrombocytopenia, the concentrations of kynurenine were detected by high-pressure liquid chromatography. The expressions of IDO were analyzed by flow cytometry and western blot analysis. The effects of IDO(+) DCs stimulated with CTLA-4-Ig on T cells proliferation and activation, lymphocyte apoptosis, and Tregs were measured by flow cytometry. We found that the expression of IDO in DCs of immune thrombocytopenia (ITP) patients was significantly decreased. CTLA-4-Ig significantly increased the expression of functional IDO in DCs of ITP patients. IDO(+) DCs stimulated with CTLA-4-Ig suppressed T cells proliferation and activation, promoted lymphocyte apoptosis, and increased the percentage of Tregs. These results suggest that decreased IDO expression in DCs may play a critical role in ITP. CTLA-4-Ig successfully corrected the disorder of IDO expression in ITP. IDO(+) DCs stimulated with CTLA-4-Ig inhibited immune responses by an IDO-dependent mechanism. Increasing the expression and activity of IDO in DCs might be a promising therapeutic approach for ITP.