The Journal of Experimental Medicine

Iñiguez, Maria; Berasain, Carmen; Martinez-Ansó, Eduardo; Bustos, Matilde; Fortes, Puri; Pennica, Diane; Avila, Matias A.; Prieto, Jesús

doi: 10.1084/jem.20061421pmid: 17178916

Ischemia-reperfusion (I/R) liver injury occurs when blood flow is restored after prolonged ischemia. A short interruption of blood flow (ischemic preconditioning IP) induces tolerance to subsequent prolonged ischemia through ill-defined mechanisms. Cardiotrophin (CT)-1, a cytokine of the interleukin-6 family, exerts hepatoprotective effects and activates key survival pathways like JAK/STAT3. Here we show that administration of CT-1 to rats or mice protects against I/R liver injury and that CT-1–deficient mice are exceedingly sensitive to this type of damage. IP markedly reduced transaminase levels and abrogated caspase-3 and c-Jun–NH 2 -terminal kinase activation after I/R in normal mice but not in CT-1–null mice. Moreover, the protective effect afforded by IP was reduced by previous administration of neutralizing anti–CT-1 antibody. Prominent STAT3 phosphorylation in liver tissue was observed after IP plus I/R in normal mice but not in CT-1–null mice. Oxidative stress, a process involved in IP-induced hepatoprotection, was found to stimulate CT-1 release from isolated hepatocytes. Interestingly, brief ischemia followed by short reperfusion caused mild serum transaminase elevation and strong STAT3 activation in normal and IL-6–deficient mice, but failed to activate STAT3 and provoked marked hypertransaminasemia in CT-1–null animals. In conclusion, CT-1 is an essential endogenous defense of the liver against I/R and is a key mediator of the protective effect induced by IP. Footnotes M.A. Avila and J. Prieto are senior authors on this paper. Submitted: 5 July 2006 Accepted: 21 November 2006

Pion, Marjorie; Granelli-Piperno, Angela; Mangeat, Bastien; Stalder, Romaine; Correa, Rafael; Steinman, Ralph M.; Piguet, Vincent

doi: 10.1084/jem.20061519pmid: 17145955

HIV-1 infects immature dendritic cells (iDCs), but infection is inefficient compared with activated CD4 + T cells and only involves a small subset of iDCs. We analyzed whether this could be attributed to specific cellular restrictions during the viral life cycle. To study env -independent restriction to HIV-1 infection, we used a single-round infection assay with HIV-1 pseudotyped with vesicular stomatitis virus G protein (HIV-VSVG). Small interfering RNA–mediated depletion of APOBEC3G/3F (A3G/3F), but not TRIM5α, enhanced HIV-1 infection of iDCs, indicating that A3G/3F controls the sensitivity of iDCs to HIV-1 infection. Furthermore, sequences of HIV reverse transcripts revealed G-to-A hypermutation of HIV genomes during iDC infection, demonstrating A3G/3F cytidine deaminase activity in iDCs. When we separated the fraction of iDCs that was susceptible to HIV, we found the cells to be deficient in A3G messenger RNA and protein. We also noted that during DC maturation, which further reduces susceptibility to infection, A3G levels increased. These findings highlight a role for A3G/3F in explaining the resistance of most DCs to HIV-1 infection, as well as the susceptibility of a fraction of iDCs. An increase in the A3G/3F-mediated intrinsic resistance of iDCs could result in a block of HIV infection at its mucosal point of entry. Footnotes Abbreviations used: A3F and A3G, APOBEC3F and APOBEC3G, respectively; iDC, immature DC; JT, Jurkat CD4 + T cell; LMM, low molecular mass; LV, lentiviral vector; mDC, monocyte-derived DC; MOI, multiplicity of infection; mRNA, messenger RNA; P, pellet; siRNA, small interfering RNA; SN, supernatant; T5α, Trim5α; VSVG, vesicular stomatitis virus G. Submitted: 18 July 2006 Accepted: 13 November 2006

Erlacher, Miriam; Labi, Verena; Manzl, Claudia; Böck, Günther; Tzankov, Alexandar; Häcker, Georg; Michalak, Ewa; Strasser, Andreas; Villunger, Andreas

doi: 10.1084/jem.20061552pmid: 17178918

The physiological role of B cell lymphoma 2 (Bcl-2) homology 3–only proteins has been investigated in mice lacking the individual genes identifying rate-limiting roles for Bim (Bcl-2–interacting mediator of cell death) and Puma (p53–up-regulated modulator of apoptosis) in apoptosis induction. The loss of Bim protects lymphocytes from apoptosis induced by cytokine deprivation and deregulated Ca ++ flux and interferes with the deletion of autoreactive lymphocytes and the shutdown of immune responses. In contrast, Puma is considered the key mediator of p53-induced apoptosis. To investigate the hypothesis that Bim and Puma have overlapping functions, we generated mice lacking both genes and found that bim −/− / puma −/− animals develop multiple postnatal defects that are not observed in the single knockout mice. Most strikingly, hyperplasia of lymphatic organs is comparable with that observed in mice overexpressing Bcl-2 in all hemopoietic cells exceeding the hyperplasia observed in bim −/− mice. Bim and Puma also have clearly overlapping functions in p53-dependent and -independent apoptosis. Their combined loss promotes spontaneous tumorigenesis, causing the malignancies observed in Bcl-2 transgenic mice, but does not exacerbate the autoimmunity observed in the absence of Bim. Footnotes Abbreviations used: ANA, antinuclear antibody; Bad, Bcl-2 antagonist of cell death; Bak, Bcl-2 antagonist/killer; Bax, Bcl-2–associated protein X; Bcl-2, B cell lymphoma 2; BH, Bcl-2 homology; Bid, Bcl-2–interacting domain death agonist; Bim, Bcl-2–interacting mediator of cell death; Blk, Bik-like killer; Bmf, Bcl-2 modifying factor; DN, double negative; DP, double positive; dsDNA, double-stranded DNA; GC, glucocorticoid; PCNA, proliferating cell nuclear antigen; PI, propidium iodide; Puma, p53–up-regulated modulator of apoptosis; SEB, Staphylococcus enterotoxin B; tg, transgenic. M. Erlacher's present address is Department of Pediatrics and Adolescent Medicine, Division of Pediatric Hematology and Oncology, University Hospital of Freiburg, 79104 Freiburg, Germany. Submitted: 24 July 2006 Accepted: 26 November 2006

Sedding, Daniel; Daniel, Jan-Marcus; Muhl, Lars; Hersemeyer, Karin; Brunsch, Hannes; Kemkes-Matthes, Bettina; Braun-Dullaeus, Ruediger C.; Tillmanns, Harald; Weimer, Thomas; Preissner, Klaus T.; Kanse, Sandip M.

doi: 10.1084/jem.20052546pmid: 17145954

The G534E polymorphism (Marburg I MI) of factor VII–activating protease (FSAP) is associated with carotid stenosis and cardiovascular disease. We have previously demonstrated that FSAP is present in atherosclerotic plaques and it is a potent inhibitor of vascular smooth muscle proliferation and migration in vitro. The effect of wild-type (WT)- and MI-FSAP on neointima formation in the mouse femoral artery after wire-induced injury was investigated. Local application of WT-FSAP led to a 70% reduction in the neointima formation, and this effect was dependent on the protease activity of FSAP. MI-FSAP did not inhibit neointima formation in vivo. This is due to a reduced proteolytic activity of MI-FSAP, compared to WT-FSAP, toward platelet-derived growth factor BB, a key mediator of neointima development. The inability of MI-FSAP to inhibit vascular smooth muscle accumulation explains the observed linkage between the MI-polymorphism and increased cardiovascular risk. Hence, FSAP has a protective function in the vasculature, and analysis of MI polymorphism is likely to be clinically relevant in restenosis. Footnotes Submitted: 23 December 2005 Accepted: 17 November 2006

Berruyer, Carole; Pouyet, Laurent; Millet, Virginie; Martin, Florent M.; LeGoffic, Aude; Canonici, Alexandra; Garcia, Stéphane; Bagnis, Claude; Naquet, Philippe; Galland, Franck

doi: 10.1084/jem.20061640pmid: 17145956

Colitis involves immune cell–mediated tissue injuries, but the contribution of epithelial cells remains largely unclear. Vanin-1 is an epithelial ectoenzyme with a pantetheinase activity that provides cysteamine/cystamine to tissue. Using the 2,4,6-trinitrobenzene sulfonic acid (TNBS)-colitis model we show here that Vanin-1 deficiency protects from colitis. This protection is reversible by administration of cystamine or bisphenol A diglycidyl ether, a peroxisome proliferator-activated receptor (PPAR)γ antagonist. We further demonstrate that Vanin-1, by antagonizing PPARγ, licenses the production of inflammatory mediators by intestinal epithelial cells. We propose that Vanin-1 is an epithelial sensor of stress that exerts a dominant control over innate immune responses in tissue. Thus, the Vanin-1/pantetheinase activity might be a new target for therapeutic intervention in inflammatory bowel disease. Footnotes Abbreviations used: ATRA, all trans-retinoic acid; BADGE, bisphenol A diglycidyl ether; COX, cyclooxygenase; 15-d-PGJ 2 , 15-deoxy-Δ 12,14 -prostaglandin J 2 ; GSH, glutathione; IBD, inflammatory bowel disease; IEC, intestinal epithelial cell; MCP, monocyte chemoattractant protein; MIP, macrophage inflammatory protein; PPAR, peroxisome proliferator-activated receptor; SCID, severe combined immunodeficient; TNBS, 2,4,6-trinitrobenzene sulfonic acid. C. Berruyer's present address is National de la Santé et de la Recherche Médicale, U599 27, 13009 Marseille, France. F.M. Martin's present address is The Scripps Research Institute, Department of Molecular and Experimental Medicine, MEM-131, La Jolla, CA 92037. Submitted: 2 August 2006 Accepted: 18 October 2006

Williams, Ruth

doi: 10.1084/jem.20313iti3pmid: N/A

Lohr, Jens; Knoechel, Birgit; Wang, Jing Jing; Villarino, Alejandro V.; Abbas, Abul K.

doi: 10.1084/jem.20061341pmid: 17130300

To explore the interactions between regulatory T cells and pathogenic effector cytokines, we have developed a model of a T cell–mediated systemic autoimmune disorder resembling graft-versus-host disease. The cytokine responsible for tissue inflammation in this disorder is interleukin (IL)-17, whereas interferon (IFN)-γ produced by Th1 cells has a protective effect in this setting. Because of the interest in potential therapeutic approaches utilizing transfer of regulatory T cells and inhibition of the IL-2 pathway, we have explored the roles of these in the systemic disease. We demonstrate that the production of IL-17 and tissue infiltration by IL-17–producing cells occur and are even enhanced in the absence of IL-2. Regulatory T cells favor IL-17 production but prevent the disease when administered early in the course by suppressing expansion of T cells. Thus, the pathogenic or protective effects of cytokines and the therapeutic capacity of regulatory T cells are crucially dependent on the timing and the nature of the disease. Footnotes J. Lohr and B. Knoechel contributed equally to this work. Submitted: 23 June 2006 Accepted: 3 November 2006

Liu, Xinqi; Zhu, Yanan; Dai, Shaodong; White, Janice; Peyerl, Fred; Kappler, John W.; Marrack, Philippa

doi: 10.1084/jem.20061151pmid: 17158961

Activated T cells die when antigen disappears from animals. This death is caused by proteins related to Bcl-2. Two hypotheses have been suggested to explain the actions of the different types of Bcl-2 proteins. One hypothesis suggests that, when T cells prepare to die, Bak and Bax, the proteins that actually kill activated T cells, are released from antiapoptotic proteins such as Bcl-2 and Bcl-xl. Another hypothesis suggests that Bak and Bax are normally free and are triggered to kill cells by release of messenger proteins, such as Bim, from Bcl-2 and Bcl-xl. Here, a form of Bcl-xl, which lacks a long unstructured loop, is used to show that the first hypothesis is not correct. Bcl-xl without its loop protects activated T cells from death, yet Bcl-xl without its loop cannot bind any form of Bak and Bax. Thus, binding of Bcl-xl to Bak or Bax is not involved in T cell life or death. The loop of Bcl-xl is also somewhat involved in Bcl-xl's binding of Bim because Bcl-xl without its loop binds Bim less well than wild-type Bcl-xl. Moreover, the loop may have additional, as yet unknown, functions because it changes its shape when Bcl-xl binds Bim. Footnotes Abbreviations used: BH3, Bcl-2 homology 3; SEB, staphylococcal enterotoxin B. X. Liu's present address is Dept. of Biological Science, Purdue University, West Lafayette, IN 47907. Y. Zhu's present address is Dept. of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94143. Submitted: 31 May 2006 Accepted: 26 November 2006

Yang, Shu Yuan; Fugmann, Sebastian D.; Schatz, David G.

doi: 10.1084/jem.20061835pmid: 17178919

It is thought that gene conversion (GCV) and somatic hypermutation (SHM) of immunoglobulin (Ig) genes occur in two steps: the generation of uracils in DNA by activation-induced cytidine deaminase, followed by their subsequent repair by various DNA repair pathways to generate sequence-diversified products. It is not known how either of the two steps is targeted specifically to Ig loci. Because of the tight link between transcription and SHM, we have investigated the role of endogenous Ig light chain (IgL) transcriptional control elements in GCV/SHM in the chicken B cell line DT40. Promoter substitution experiments led to identification of a strong RNA polymerase II promoter incapable of supporting efficient GCV/SHM. This surprising finding indicates that high levels of transcription are not sufficient for robust GCV/SHM in Ig loci. Deletion of the IgL enhancer in a context in which high-level transcription was not compromised showed that the enhancer is not necessary for GCV/SHM. Our results indicate that cis-acting elements are important for Ig gene diversification, and we propose that targeting specificity is achieved through the combined action of several Ig locus elements that include the promoter. Footnotes Abbreviations used: AID, activation-induced cytidine deaminase; EF1-α, elongation factor 1-α; GCV, gene conversion; IgH, Ig heavy chain; Igκ, Ig light chain κ; IgL, Ig light chain; SHM, somatic hypermutation. S.D. Fugmann's present address is National Institute on Aging, National Institutes of Health, Baltimore, MD 21224. Submitted: 28 August 2006 Accepted: 20 November 2006

Harada, Michishige; Magara-Koyanagi, Kumiko; Watarai, Hiroshi; Nagata, Yuko; Ishii, Yasuyuki; Kojo, Satoshi; Horiguchi, Shigetoshi; Okamoto, Yoshitaka; Nakayama, Toshinori; Suzuki, Nobutaka; Yeh, Wen-Chen; Akira, Shizuo; Kitamura, Hiroshi; Ohara, Osamu; Seino, Ken-ichiro; Taniguchi, Masaru