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Receptor-interacting protein kinase 1 (RIPK1) regulates cell death and inflammation. Here, we show that T cell–specific RIPK1 deficiency in mice leads to the premature senescence of T cells and induces various age-related diseases, resulting in premature death. RIPK1 deficiency causes higher basal activation of mTORC1 (mechanistic target of rapamycin complex 1) that drives enhanced cytokine production, induction of senescence-related genes, and increased activation of caspase-3/7, which are restored by inhibition of mTORC1. Critically, normal aged T cells exhibit similar phenotypes and responses. Mechanistically, a combined deficiency of RIPK3 and caspase-8 inhibition restores the impaired proliferative responses; the elevated activation of Akt, mTORC1, extracellular signal–regulated kinase, and caspase-3/7; and the increased expression of senescence-related genes in RIPK1-deficient CD4 T cells. Last, we revealed that the senescent phenotype of RIPK1-deficient and aged CD4 T cells is restored in the normal tissue environment. Thus, we have clarified the function of RIPK3 and caspase-8 in inducing CD4 T cell senescence, which is modulated by environmental signals.

Summary Effector, but not naive, T cells are activated by toll-like receptor-2 (TLR2) stimulation, leading to cytokine production and proliferation. We found that the differential response is attributable to the lack of expression of the adaptor protein TIRAP in naive T cells. TIRAP expression is induced upon T-cell receptor (TCR) stimulation and sustained by strong interleukin-2 (IL-2) signals. Expression of TIRAP requires TCR- and IL-2-induced mTORC1 activation. TLR2 stimulation induced the activation of nuclear factor κB (NF-κB) and ERK, leading to much higher production of interferon-γ (IFN-γ) by T helper 1 (Th1) cells cultured in a high concentration of IL-2 than by those cultured in a low concentration of IL-2. In contrast, TLR2 stimulation induces mTORC1 activation through TIRAP, which is essential for TLR2-mediated IFN-γ production. These data demonstrate that the mTORC1 signal confers the response to TLR2 signaling by inducing TIRAP expression and that the TIRAP-mTORC1 axis is critical for TLR2-mediated IFN-γ production by effector T cells.

Background Postoperative pancreatic fistula (POPF) remains a major cause of morbidity after distal pancreatectomy. The aim of this study was to investigate whether duct-to-mucosa pancreaticogastrostomy of the pancreatic stump decreased clinical POPF formation compared with handsewn closure after distal pancreatectomy. Methods This multicentre RCT was performed between April 2012 and June 2014. Patients undergoing distal pancreatectomy were assigned randomly to either duct-to-mucosa pancreaticogastrostomy or handsewn closure. The primary endpoint was the incidence of clinical POPF. Secondary endpoints were rates of other complications and length of hospital stay. Results Some 80 patients were randomized, and 73 patients were evaluated in an intention-to-treat analysis: 36 in the pancreaticogastrostomy group and 37 in the handsewn closure group. The duration of operation was significantly longer in the pancreaticogastrostomy group than in the handsewn closure group (mean 268 versus 197 min respectively; P < 0·001). The incidence of clinical POPF did not differ between groups (7 of 36 versus 7 of 37; odds ratio (OR) 1·03, 95 per cent c.i. 0·32 to 3·10; P = 1·000). The rate of intra-abdominal fluid collection was significantly lower in the pancreaticogastrostomy group (6 of 36 versus 21 of 37; OR 0·15, 0·05 to 0·45; P < 0·001). There were no statistically significant differences in the rates of other complications or length of hospital stay. Conclusion Duct-to-mucosa pancreaticogastrostomy did not reduce the incidence of clinical POPF compared with handsewn closure of the pancreatic stump after distal pancreatectomy. Registration number UMIN000007426 (http://www.umin.ac.jp).

Background Although mortality associated with pancreatic surgery has decreased dramatically, high morbidity rates are still of major concern. This study aimed to identify the prevalence of, and risk factors for, infectious complications after pancreatic surgery. Methods The Japanese Society of Pancreatic Surgery conducted a multi-institutional analysis of complications in patients who underwent pancreaticoduodenectomy (PD) or distal pancreatectomy (DP) between January 2010 and December 2012. Risk factors that were significantly associated with infectious complications in univariable models were included in a multivariable logistic regression model, and a nomogram was created to predict the risk of infectious complications after pancreatectomy. Results Infectious complications occurred in 1459 (35·2 per cent) of 4147 patients in the PD group and 426 (25·2 per cent) of 1692 patients in the DP group (P < 0·001). Nine risk factors for infectious complications after PD were identified: male sex, age 70 years or more, body mass index at least 25 kg/m2, other previous malignancy, liver disease, bile contamination, duration of surgery 7 h or longer, intraoperative blood transfusion and soft pancreas. Five risk factors for infectious complications after DP were identified: chronic steroid use, smoking, duration of surgery 5 h or more, intraoperative blood transfusion and non-laparoscopic surgery. Occurrence of a postoperative infectious complication was significantly associated with mortality and reoperation after PD (odds ratio (OR) 4·33, 95 per cent c.i. 2·01 to 9·92 and OR 3·26, 1·86 to 5·82, respectively) and DP (OR 6·32, 1·99 to 22·55; OR 3·74, 1·61 to 9·04). Conclusion Prolonged operating time, intraoperative blood transfusion, bile contamination (PD) and non-laparoscopic surgery (DP) are risk factors for postoperative infectious complications that could be targeted to improve outcome after pancreatectomy.

Costimulation of T cells through both TCR and STING induces growth inhibition by partially blocking the mTORC1 signals, and leads to IFN-I production through sustained activation of IRF3 and mTORC1 activation., Stimulator of interferon genes (STING) plays a key role in detecting cytosolic DNA and induces type I interferon (IFN-I) responses for host defense against pathogens. Although T cells highly express STING, its physiological role remains unknown. Here, we show that costimulation of T cells with the STING ligand cGAMP and TCR leads to IFN-I production and strongly inhibits T-cell growth. TCR-mediated mTORC1 activation and sustained activation of IRF3 are required for cGAMP-induced IFN-I production, and the mTORC1 activity is partially counteracted by cGAMP, thereby blocking proliferation. This mTORC1 inhibition in response to costimulation depends on IRF3 and IRF7. Effector T cells produce much higher IFN-I levels than innate cells in response to cGAMP. Finally, we demonstrated that STING stimulation in T cells is effective in inducing antitumor responses in vivo. Our studies demonstrate that the outputs of STING and TCR signaling pathways are mutually regulated through mTORC1 to modulate T-cell functions.

Background The International Union Against Cancer (UICC) staging system for perihilar cholangiocarcinoma changed in 2009. The aim of this study was to validate and optimize the UICC system for these tumours. Methods This retrospective study was conducted in eight Japanese hospitals between 2001 and 2010. Perihilar cholangiocarcinoma was defined as a cholangiocarcinoma that involves the hilar bile duct, independent of the presence or absence of a liver mass component. The stratification ability of the UICC tumour node metastasis (TNM) system was compared with that of a modified system. Results Of 1352 patients, 35·9, 44·8 and 12·6 per cent had Bismuth type IV tumours, nodal metastasis (N1) and distant metastasis (M1) respectively. T4 tumours (43·2 per cent) and stage IVA (T4 Nany M0; 36·3 per cent) disease were most common. Survival was not significantly different between patients with T3versus T4 tumours (P = 0·284). Survival for patients with stage IVA disease was comparable to that for patients with stage IIIB tumours (T1–3 N1 M0) (P = 0·426). Vascular invasion, pancreatic invasion, positive margin, N1 and M1 status were identified as independent predictors of survival. When Bismuth type IV tumours were removed from the T4 determinants and N1 tumours grouped together, the modified grouping had a higher linear trend χ2 and likelihood ratio χ2 compared with the original system (245·6 versus 170·3 respectively and 255·8 versus 209·3 respectively). Conclusion The present data suggest that minimal modification with removal of Bismuth type IV tumours from the T4 determinants and bundling of N1 disease may enhance the prognostic ability of the UICC system. However, this requires validation on an independent data set.

The transcriptional repressor BTB and CNC homology 2 (Bach2) is thought to be mainly expressed in B cells with specific functions such as class switch recombination and somatic hypermutation, but its function in T cells is not known. We found equal Bach2 expression in T cells and analyzed its function using Bach2-deficient (−/−) mice. Although T-cell development was normal, numbers of peripheral naive T cells were decreased, which rapidly produced Th2 cytokines after TCR stimulation. Bach2 −/− naive T cells highly expressed genes related to effector-memory T cells such as CCR4, ST-2 and Blimp-1. Enhanced expression of these genes induced Bach2 −/− naive T cells to migrate toward CCR4-ligand and respond to IL33. Forced expression of Bach2 restored the expression of these genes. Using Chromatin Immunoprecipitation (ChIP)-seq analysis, we identified S100 calcium binding protein a, Heme oxigenase 1, and prolyl hydroxylase 3 as Bach2 direct target genes, which are highly expressed in effector-memory T cells. These findings indicate that Bach2 suppresses effector memory-related genes to maintain the naive T-cell state and regulates generation of effector-memory T cells.

IRAK-4 is a protein kinase that is pivotal in mediating signals for innate immune responses. Here, we report that IRAK-4 signaling is also essential for eliciting adaptive immune responses. Thus, in the absence of IRAK-4, in vivo T cell responses were significantly impaired. Upon T cell receptor stimulation, IRAK-4 is recruited to T cell lipid rafts, where it induces downstream signals, including protein kinase Cθ activation through the association with Zap70. This signaling pathway was found to be required for optimal activation of nuclear factor κB. Our findings suggest that T cells use this critical regulator of innate immunity for the development of acquired immunity, suggesting that IRAK-4 may be involved in direct signal cross talk between the two systems.

NK cells and CD8+ T cells exhibit cytotoxicity and cytokine production upon recognizing target cells through cell-cell interaction. We screened the molecules involved in the recognition and regulation of these cells using cDNA subtraction between naive and activated NK cells. We identified class I-restricted T cell-associated molecule (CRTAM), a two Ig domain-bearing surface receptor, as a molecule rapidly and transiently expressed on NK cells and CD8+ T cells upon activation. CRTAM is expressed as a dimer on the cell surface, and its expression is transcriptionally regulated. Using an expression-cloning system, we then further identified Nectin-like (Necl) molecule 2, a three Ig domain-containing receptor, as a ligand of CRTAM. While Necl2 mediates homotypic interaction, CRTAM interacts with Necl2 but not with CRTAM itself. The heterotypic CRTAM-Necl2 interaction has a higher affinity than the homotypic Necl2 interaction. Although there was no clear alteration in the cytotoxic function of the NK cells and CD8+ T cells against the Necl2-expressing target cells, T cells expressing CRTAM tightly bound to Necl2-expressing cells. CRTAM+ cells did not induce homotypic aggregation but they did exert strong heterotypic binding with Necl2+ cells, which was inhibited by the addition of the CRTAM-Ig fusion protein. These results suggest that the heterotypic interaction between CRTAM and Necl2 plays an important role in the adhesion, interaction or migration of NK cells and CD8+ T cells upon stimulation.