Ectopic expression of CC chemokine ligand 21 (CCL21) in the thyroid leads to development of lymphoid structures that resemble those observed in Hashimoto thyroiditis. Deletion of the inhibitor of differentiation 2 (Id2) gene, essential for generation of CD3–CD4+ lymphoid tissue–inducer (LTi) cells and development of secondary lymphoid organs, did not affect formation of tertiary lymphoid structures. Rather, mature CD3+CD4+ T cells were critical for the development of tertiary lymphoid structures. The initial stages of this process involved interaction of CD3+CD4+ T cells with DCs, the appearance of peripheral-node addressin–positive (PNAd+) vessels, and production of chemokines that recruit lymphocytes and DCs. These findings indicate that the formation of tertiary lymphoid structures does not require Id2-dependent conventional LTis but depends on a program initiated by mature CD3+CD4+ T cells.
Tatjana Marinkovic, Alexandre Garin, Yoshifumi Yokota, Yang-Xin Fu, Nancy H. Ruddle, Glaucia C. Furtado, Sergio A. Lira
IFN-γ is an important Th1 proinflammatory cytokine and has a paradoxical effect on EAE in which disease susceptibility is unexpectedly heightened in IFN-γ–deficient mice. In this study, we provide what we believe is new evidence indicating that IFN-γ is critically required for the conversion of CD4+CD25– T cells to CD4+ Tregs during EAE. In our study, the added severity of EAE in IFN-γ knockout mice was directly associated with altered encephalitogenic T cell responses, which correlated with reduced frequency and function of CD4+CD25+Foxp3+ Tregs when compared with those of WT mice. It was demonstrated in both human and mouse systems that in vitro IFN-γ treatment of CD4+CD25– T cells led to conversion of CD4+ Tregs as characterized by increased expression of Foxp3 and enhanced regulatory function. Mouse CD4+CD25– T cells, when treated in vitro with IFN-γ, acquired marked regulatory properties as evidenced by suppression of EAE by adoptive transfer. These findings have important implications for the understanding of the complex role of IFN-γ in both induction and self regulation of inflammatory processes.
Zhaojun Wang, Jian Hong, Wei Sun, Guangwu Xu, Ningli Li, Xi Chen, Ailian Liu, Lingyun Xu, Bing Sun, Jingwu Z. Zhang
TNF-related apoptosis–inducing ligand (TRAIL) is a member of the TNF family with potent apoptosis-inducing properties in tumor cells. In particular, TRAIL strongly synergizes with conventional chemotherapeutic drugs to induce tumor cell death. Thus, TRAIL has been proposed as a promising future cancer therapy. Little, however, is known regarding what the role of TRAIL is in normal untransformed cells and whether therapeutic administration of TRAIL, alone or in combination with other apoptotic triggers, may cause tissue damage. In this study, we investigated the role of TRAIL in Fas-induced (CD95/Apo-1–induced) hepatocyte apoptosis and liver damage. While TRAIL alone failed to induce apoptosis in isolated murine hepatocytes, it strongly amplified Fas-induced cell death. Importantly, endogenous TRAIL was found to critically regulate anti-Fas antibody–induced hepatocyte apoptosis, liver damage, and associated lethality in vivo. TRAIL enhanced anti-Fas–induced hepatocyte apoptosis through the activation of JNK and its downstream substrate, the proapoptotic Bcl-2 homolog Bim. Consistently, TRAIL- and Bim-deficient mice and wild-type mice treated with a JNK inhibitor were protected against anti-Fas–induced liver damage. We conclude that TRAIL and Bim are important response modifiers of hepatocyte apoptosis and identify liver damage and lethality as a possible risk of TRAIL-based tumor therapy.
Nadia Corazza, Sabine Jakob, Corinne Schaer, Steffen Frese, Adrian Keogh, Deborah Stroka, Daniela Kassahn, Ralph Torgler, Christoph Mueller, Pascal Schneider, Thomas Brunner
Sepsis results in a state of relative immunosuppression, rendering critically ill patients susceptible to secondary infections and increased mortality. Monocytes isolated from septic patients and experimental animals display a “deactivated” phenotype, characterized by impaired inflammatory and antimicrobial responses, including hyporesponsiveness to LPS. We investigated the role of the LPS/TLR4 axis and its inhibitor, IL-1 receptor–associated kinase–M (IRAK-M), in modulating the immunosuppression of sepsis using a murine model of peritonitis-induced sepsis followed by secondary challenge by intratracheal Pseudomonasaeruginosa. Septic mice demonstrated impaired alveolar macrophage function and increased mortality when challenged with intratracheal Pseudomonas as compared with nonseptic controls. TLR2 and TLR4 expression was unchanged in the lung following sepsis, whereas levels of IRAK-M were upregulated. Macrophages from IRAK-M–deficient septic mice produced higher levels of proinflammatory cytokines ex vivo and greater costimulatory molecule expression in vivo as compared with those of their WT counterparts. Following sepsis and secondary intrapulmonary bacterial challenge, IRAK-M–/– animals had higher survival rates and improved bacterial clearance from lung and blood compared with WT mice. In addition, increased pulmonary chemokine and inflammatory cytokine production was observed in IRAK-M–/– animals, leading to enhanced neutrophil recruitment to airspaces. Collectively, these findings indicate that IRAK-M mediates critical aspects of innate immunity that result in an immunocompromised state during sepsis.
Jane C. Deng, Genhong Cheng, Michael W. Newstead, Xianying Zeng, Koichi Kobayashi, Richard A. Flavell, Theodore J. Standiford
One of the greatest barriers against harnessing the potential of CD4+CD25+ Tregs as a cellular immunotherapy is their hypoproliferative phenotype. We have previously shown that the hypoproliferative response of Tregs to IL-2 is associated with defective downstream PI3K signaling. Here, we demonstrate that targeted deletion of the lipid phosphatase PTEN (phosphatase and tensin homolog deleted on chromosome 10) regulates the peripheral homeostasis of Tregs in vivo and allows their expansion ex vivo in response to IL-2 alone. PTEN deficiency does not adversely affect either the thymic development or the function of Tregs, which retain their ability to suppress responder T cells in vitro and prevent colitis in vivo. Conversely, reexpression of PTEN in PTEN-deficient Tregs as well as in activated CD4+ T cells inhibits IL-2–dependent proliferation, confirming PTEN as a negative regulator of IL-2 receptor signaling. These data demonstrate that PTEN regulates the “anergic” response of Tregs to IL-2 in vitro and Treg homeostasis in vivo and indicate that inhibition of PTEN activity may facilitate the expansion of these cells for potential use in cellular immunotherapy.
Patrick T. Walsh, Jodi L. Buckler, Jidong Zhang, Andrew E. Gelman, Nicole M. Dalton, Devon K. Taylor, Steven J. Bensinger, Wayne W. Hancock, Laurence A. Turka
While memory T cells are maintained by continuous turnover, it is not clear how human regulatory CD4+CD45RO+CD25hi Foxp3+ T lymphocyte populations persist throughout life. We therefore used deuterium labeling of cycling cells in vivo to determine whether these cells could be replenished by proliferation. We found that CD4+CD45RO+Foxp3+CD25hi T lymphocytes were highly proliferative, with a doubling time of 8 days, compared with memory CD4+CD45RO+Foxp3–CD25– (24 days) or naive CD4+CD45RA+Foxp3–CD25– populations (199 days). However, the regulatory population was susceptible to apoptosis and had critically short telomeres and low telomerase activity. It was therefore unlikely to be self regenerating. These data are consistent with continuous production from another population source. We found extremely close TCR clonal homology between regulatory and memory CD4+ T cells. Furthermore, antigen-related expansions within certain TCR Vβ families were associated with parallel numerical increases of CD4+CD45RO+CD25hiFoxp3+ Tregs with the same Vβ usage. It is therefore unlikely that all human CD4+CD25+Foxp3+ Tregs are generated as a separate functional lineage in the thymus. Instead, our data suggest that a proportion of this regulatory population is generated from rapidly dividing, highly differentiated memory CD4+ T cells; this has considerable implications for the therapeutic manipulation of these cells in vivo.
Milica Vukmanovic-Stejic, Yan Zhang, Joanne E. Cook, Jean M. Fletcher, Arthur McQuaid, Joanne E. Masters, Malcolm H.A. Rustin, Leonie S. Taams, Peter C.L. Beverley, Derek C. Macallan, Arne N. Akbar
The adipocyte fatty acid–binding protein aP2 regulates systemic glucose and lipid metabolism. We report that aP2, in addition to being abundantly expressed by adipocytes, is also expressed by human airway epithelial cells and shows a striking upregulation following stimulation of epithelial cells with the Th2 cytokines IL-4 and IL-13. Regulation of aP2 mRNA expression by Th2 cytokines was highly dependent on STAT6, a transcription factor with a major regulatory role in allergic inflammation. We examined aP2-deficient mice in a model of allergic airway inflammation and found that infiltration of leukocytes, especially eosinophils, into the airways was highly dependent on aP2 function. T cell priming was unaffected by aP2 deficiency, suggesting that aP2 was acting locally within the lung, and analysis of bone marrow chimeras implicated non-hematopoietic cells, most likely bronchial epithelial cells, as the site of action of aP2 in allergic airway inflammation. Thus, aP2 regulates allergic airway inflammation and may provide a link between fatty acid metabolism and asthma.
Bennett O.V. Shum, Charles R. Mackay, Cem Z. Gorgun, Melinda J. Frost, Rakesh K. Kumar, Gökhan S. Hotamisligil, Michael S. Rolph
Anaphylactic shock is a sudden, life-threatening allergic reaction associated with severe hypotension. Platelet-activating factor (PAF) is implicated in the cardiovascular dysfunctions occurring in various shock syndromes, including anaphylaxis. Excessive production of the vasodilator NO causes inflammatory hypotension and shock, and it is generally accepted that transcriptionally regulated inducible iNOS is responsible for this. Nevertheless, the contribution of NO to PAF-induced shock or anaphylactic shock is still ambiguous. We studied PAF and anaphylactic shock in conscious mice. Surprisingly, hyperacute PAF shock depended entirely on NO, produced not by inducible iNOS, but by constitutive eNOS, rapidly activated via the PI3K pathway. Soluble guanylate cyclase (sGC) is generally regarded as the principal vasorelaxing mediator of NO. Nevertheless, although methylene blue partially prevented PAF shock, neither 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one (ODQ) nor sGCα1 deficiency did. Also, in 2 different models of active systemic anaphylaxis, inhibition of NOS, PI3K, or Akt or eNOS deficiency provided complete protection. In contrast to the unsubstantiated paradigm that only excessive iNOS-derived NO underlies cardiovascular collapse in shock, our data strongly support the unexpected concept that eNOS-derived NO is the principal vasodilator in anaphylactic shock and define eNOS and/or PI3K or Akt as new potential targets for treating anaphylaxis.
Anje Cauwels, Ben Janssen, Emmanuel Buys, Patrick Sips, Peter Brouckaert
While it has long been known that inflammation and infection reduce expression of hepatic cytochrome P450 (CYP) genes involved in xenobiotic metabolism and that exposure to xenobiotic chemicals can impair immune function, the molecular mechanisms underlying both of these phenomena have remained largely unknown. Here we show that activation of the nuclear steroid and xenobiotic receptor (SXR) by commonly used drugs in humans inhibits the activity of NF-κB, a key regulator of inflammation and the immune response. NF-κB target genes are upregulated and small bowel inflammation is significantly increased in mice lacking the SXR ortholog pregnane X receptor (PXR), thereby demonstrating a direct link between SXR and drug-mediated antagonism of NF-κB. Interestingly, NF-κB activation reciprocally inhibits SXR and its target genes whereas inhibition of NF-κB enhances SXR activity. This SXR/PXR–NF-κB axis provides a molecular explanation for the suppression of hepatic CYP mRNAs by inflammatory stimuli as well as the immunosuppressant effects of xenobiotics and SXR-responsive drugs. This mechanistic relationship has clinical consequences for individuals undergoing therapeutic exposure to the wide variety of drugs that are also SXR agonists.
Changcheng Zhou, Michelle M. Tabb, Edward L. Nelson, Felix Grün, Suman Verma, Asal Sadatrafiei, Min Lin, Shyamali Mallick, Barry M. Forman, Kenneth E. Thummel, Bruce Blumberg
CTL-associated antigen 4 (CTLA-4) engagement negatively regulates T cell activation and function and promotes immune tolerance. However, it has been difficult to explore the biology of selective engagement of CTLA-4 in vivo because CTLA-4 shares its ligands, B7-1 and B7-2, with CD28. To address this issue, we developed a Tg mouse expressing a single-chain, membrane-bound anti–CTLA-4 Ab (scFv) on B cells. B and T cells developed normally and exhibited normal phenotype in the steady state and after activation in these mice. However, B cells from scFv Tg+ mice (scαCTLA4+) prevented T cell proliferation and cytokine production in mixed lymphocyte reactions. Additionally, mice treated with scαCTLA4+ B cells had decreased T cell–dependent B cell Ab production and class switching in vivo after antigen challenge. Furthermore, expression of this CTLA-4 agonist protected NOD mice from spontaneous autoimmune diabetes. Finally, this disease prevention occurred in Treg-deficient NOD.B7-1/B7-2 double-knockout mice, suggesting that the effect of the CTLA-4 agonist directly attenuates autoreactive T cell activation, not Treg activation. Together, results from this study demonstrate that selective ligation of CTLA-4 attenuates in vivo T cell responses, prevents development of autoimmunity, and represents a novel immunotherapeutic approach for the induction and maintenance of peripheral tolerance.
Brian T. Fife, Matthew D. Griffin, Abul K. Abbas, Richard M. Locksley, Jeffrey A. Bluestone