Wiskott-Aldrich syndrome (WAS) is a primary immunodeficiency associated with an increased susceptibility to herpesvirus infection and hematologic malignancy as well as a deficiency of NK cell function. It is caused by defective WAS protein (WASp). WASp facilitates filamentous actin (F-actin) branching and is required for F-actin accumulation at the NK cell immunological synapse and NK cell cytotoxicity ex vivo. Importantly, the function of WASp-deficient NK cells can be restored in vitro after exposure to IL-2, but the mechanisms underlying this remain unknown. Using a WASp inhibitor as well as cells from patients with WAS, we have defined a direct effect of IL-2 signaling upon F-actin that is independent of WASp function. We found that IL-2 treatment of a patient with WAS enhanced the cytotoxicity of their NK cells and the F-actin content at the immunological synapses formed by their NK cells. IL-2 stimulation of NK cells in vitro activated the WASp homolog WAVE2, which was required for inducing WASp-independent NK cell function, but not for baseline activity. Thus, WAVE2 and WASp define parallel pathways to F-actin reorganization and function in human NK cells; although WAVE2 was not required for NK cell innate function, it was accessible through adaptive immunity via IL-2. These results demonstrate how overlapping cytoskeletal activities can utilize immunologically distinct pathways to achieve synonymous immune function.
Jordan S. Orange, Sumita Roy-Ghanta, Emily M. Mace, Saumya Maru, Gregory D. Rak, Keri B. Sanborn, Anders Fasth, Rushani Saltzman, Allison Paisley, Linda Monaco-Shawver, Pinaki P. Banerjee, Rahul Pandey
Allergic asthma is characterized by airway hyperresponsiveness, inflammation, and a cellular infiltrate dominated by eosinophils. Numerous epidemiological studies have related the exacerbation of allergic asthma with an increase in ambient inhalable particulate matter from air pollutants. This is because inhalable particles efficiently deliver airborne allergens deep into the airways, where they can aggravate allergic asthma symptoms. However, the cellular mechanisms by which inhalable particulate allergens (pAgs) potentiate asthmatic symptoms remain unknown, in part because most in vivo and in vitro studies exploring the pathogenesis of allergic asthma use soluble allergens (sAgs). Using a mouse model of allergic asthma, we found that, compared with their sAg counterparts, pAgs triggered markedly heightened airway hyperresponsiveness and pulmonary eosinophilia in allergen-sensitized mice. Mast cells (MCs) were implicated in this divergent response, as the differences in airway inflammatory responses provoked by the physical nature of the allergens were attenuated in MC-deficient mice. The pAgs were found to mediate MC-dependent responses by enhancing retention of pAg/IgE/FcεRI complexes within lipid raft–enriched, CD63+ endocytic compartments, which prolonged IgE/FcεRI-initiated signaling and resulted in heightened cytokine responses. These results reveal how the physical attributes of allergens can co-opt MC endocytic circuitry and signaling responses to aggravate pathological responses of allergic asthma in mice.
Cong Jin, Christopher P. Shelburne, Guojie Li, Erin N. Potts, Kristina J. Riebe, Gregory D. Sempowski, W. Michael Foster, Soman N. Abraham
Th17 cells are a subset of CD4+ T cells with an important role in clearing certain bacterial and fungal pathogens. However, they have also been implicated in autoimmune diseases such as multiple sclerosis. Exposure of naive CD4+ T cells to IL-6 and TGF-β leads to Th17 cell differentiation through a process in which many proteins have been implicated. We report here that ectopic expression of liver X receptor (LXR) inhibits Th17 polarization of mouse CD4+ T cells, while LXR deficiency promotes Th17 differentiation in vitro. LXR activation in mice ameliorated disease in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis, whereas LXR deficiency exacerbated disease. Further analysis revealed that Srebp-1, which is encoded by an LXR target gene, mediated the suppression of Th17 differentiation by binding to the E-box element on the Il17 promoter, physically interacting with aryl hydrocarbon receptor (Ahr) and inhibiting Ahr-controlled Il17 transcription. The putative active site (PAS) domain of Ahr and the N-terminal acidic region of Srebp-1 were essential for this interaction. Additional analyses suggested that similar LXR-dependent mechanisms were operational during human Th17 differentiation in vitro. This study reports what we believe to be a novel signaling pathway underlying LXR-mediated regulation of Th17 cell differentiation and autoimmunity.
Guoliang Cui, Xia Qin, Lili Wu, Yuebo Zhang, Xiaoyan Sheng, Qiwen Yu, Hongguang Sheng, Beili Xi, Jingwu Z. Zhang, Ying Qin Zang
RHO family proteins are important for the function of inflammatory cells. They are modified with a 20-carbon geranylgeranyl lipid in a process catalyzed by protein geranylgeranyltransferase type I (GGTase-I). Geranylgeranylation is viewed as essential for the membrane targeting and activity of RHO proteins. Consequently, inhibiting GGTase-I to interfere with RHO protein activity has been proposed as a strategy to treat inflammatory disorders. However, here we show that mice lacking GGTase-I in macrophages develop severe joint inflammation resembling erosive rheumatoid arthritis. The disease was initiated by the GGTase-I–deficient macrophages and was transplantable and reversible in bone marrow transplantation experiments. The cells accumulated high levels of active GTP-bound RAC1, CDC42, and RHOA, and RAC1 remained associated with the plasma membrane. Moreover, GGTase-I deficiency activated p38 and NF-κB and increased the production of proinflammatory cytokines. The results challenge the view that geranylgeranylation is essential for the activity and localization of RHO family proteins and suggest that reduced geranylgeranylation in macrophages can initiate erosive arthritis.
Omar M. Khan, Mohamed X. Ibrahim, Ing-Marie Jonsson, Christin Karlsson, Meng Liu, Anna-Karin M. Sjogren, Frida J. Olofsson, Mikael Brisslert, Sofia Andersson, Claes Ohlsson, Lillemor Mattsson Hultén, Maria Bokarewa, Martin O. Bergo
Type 1 or invariant NKT (iNKT) cell agonists, epitomized by α-galactosylceramide, protect against cancer largely by IFN-γ–dependent mechanisms. Here we describe what we believe to be a novel IFN-γ–independent mechanism induced by β-mannosylceramide, which also defines a potentially new class of iNKT cell agonist, with an unusual β-linked sugar. Like α-galactosylceramide, β-mannosylceramide directly activates iNKT cells from both mice and humans. In contrast to α-galactosylceramide, protection by β-mannosylceramide was completely dependent on NOS and TNF-α, neither of which was required to achieve protection with α-galactosylceramide. Moreover, at doses too low for either alone to protect, β-mannosylceramide synergized with α-galactosylceramide to protect mice against tumors. These results suggest that treatment with β-mannosylceramide provides a distinct mechanism of tumor protection that may allow efficacy where other agonists have failed. Furthermore, the ability of β-mannosylceramide to synergize with α-galactosylceramide suggests treatment with this class of iNKT agonist may provide protection against tumors in humans.
Jessica J. O’Konek, Petr Illarionov, Deborah Stewart Khursigara, Elena Ambrosino, Liat Izhak, Bernard F. Castillo II, Ravinder Raju, Maryam Khalili, Hee-Yong Kim, Amy R. Howell, Gurdyal S. Besra, Steven A. Porcelli, Jay A. Berzofsky, Masaki Terabe
Inherited immunodeficiency disorders can be caused by mutations in any one of a large number of genes involved in the function of immune cells. Here, we describe two families with an autosomal recessive inherited immunodeficiency disorder characterized by increased susceptibility to infection and autoimmunity. Genetic linkage studies mapped the disorder to chromosomal region 14q11.2, and a homozygous guanine-to-adenine substitution was identified at the last base of exon 3 immediately following the translational termination codon in the TCRα subunit constant gene (TRAC). RT-PCR analysis in the two affected individuals revealed impaired splicing of the mRNA, as exon 3 was lost from the TRAC transcript. The mutant TCRα chain protein was predicted to lack part of the connecting peptide domain and all of the transmembrane and cytoplasmic domains, which have a critical role in the regulation of the assembly and/or intracellular transport of TCR complexes. We found that T cells from affected individuals were profoundly impaired for surface expression of the TCRαβ complex. We believe this to be the first report of a disease-causing human TRAC mutation. Although the absence of TCRαβ+ T cells in the affected individuals was associated with immune dysregulation and autoimmunity, they had a surprising level of protection against infection.
Neil V. Morgan, Sarah Goddard, Tony S. Cardno, David McDonald, Fatimah Rahman, Dawn Barge, Andrew Ciupek, Anna Straatman-Iwanowska, Shanaz Pasha, Mary Guckian, Graham Anderson, Aarnoud Huissoon, Andrew Cant, Warren P. Tate, Sophie Hambleton, Eamonn R. Maher
E-series resolvins are antiinflammatory and pro-resolving lipid mediators derived from the ω-3 polyunsaturated fatty acid eicosapentaenoic acid (EPA) that actively clear inflammation to promote tissue homeostasis. Aspirin, in addition to exerting antithrombotic actions, also triggers the biosynthesis of these specialized pro-resolving mediators. Here, we used metabolomic profiling to investigate the biosynthesis of E-series resolvins with specific chiral chemistry in serum from human subjects and present evidence for new 18S series resolvins. Aspirin increased endogenous formation of 18S-hydroxyeicosapentaenoate (18S-HEPE) compared with 18R-HEPE, a known resolvin precursor. Human recombinant 5-lipoxygenase used both enantiomers as substrates, and recombinant LTA4 hydrolase (LTA4H) converted chiral 5S(6)-epoxide–containing intermediates to resolvin E1 and 18S-resolvin E1 (RvE1 and 18S-RvE1, respectively). 18S-RvE1 bound to the leukocyte GPCRs ChemR23 and BLT1 with increased affinity and potency compared with the R-epimer, but was more rapidly inactivated than RvE1 by dehydrogenase. Like RvE1, 18S-RvE1 enhanced macrophage phagocytosis of zymosan, E. coli, and apoptotic neutrophils and reduced both neutrophil infiltration and proinflammatory cytokines in murine peritonitis. These results demonstrate two parallel stereospecific pathways in the biosynthesis of E-series resolvins, 18R- and 18S-, which are antiinflammatory, pro-resolving, and non-phlogistic and may contribute to the beneficial actions of aspirin and ω-3 polyunsaturated fatty acids.
Sungwhan F. Oh, Padmini S. Pillai, Antonio Recchiuti, Rong Yang, Charles N. Serhan
Autoimmune diseases develop in approximately 5% of humans. They can arise when self-tolerance checkpoints of the immune system are bypassed as a consequence of inherited mutations of key genes involved in lymphocyte activation, survival, or death. For example, autoimmune lymphoproliferative syndrome (ALPS) results from defects in self-tolerance checkpoints as a consequence of mutations in the death receptor–encoding gene TNF receptor superfamily, member 6 (TNFRSF6; also known as FAS). However, some mutation carriers remain asymptomatic throughout life. We have now demonstrated in 7 ALPS patients that the disease develops as a consequence of an inherited TNFRSF6 heterozygous mutation combined with a somatic genetic event in the second TNFRSF6 allele. Analysis of the patients’ CD4–CD8– (double negative) T cells — accumulation of which is a hallmark of ALPS — revealed that in these cells, 3 patients had somatic mutations in their second TNFRSF6 allele, while 4 patients had loss of heterozygosity by telomeric uniparental disomy of chromosome 10. This observation provides the molecular bases of a nonmalignant autoimmune disease development in humans and may shed light on the mechanism underlying the occurrence of other autoimmune diseases.
Aude Magerus-Chatinet, Bénédicte Neven, Marie-Claude Stolzenberg, Cécile Daussy, Peter D. Arkwright, Nina Lanzarotti, Catherine Schaffner, Sophie Cluet-Dennetiere, Filomeen Haerynck, Gérard Michel, Christine Bole-Feysot, Mohammed Zarhrate, Isabelle Radford-Weiss, Serge P. Romana, Capucine Picard, Alain Fischer, Frédéric Rieux-Laucat
NKT cells in the mouse recognize antigen in the context of the MHC class I–like molecule CD1d and play an important role in peripheral tolerance and protection against autoimmune and other diseases. NKT cells are usually activated by CD1d-presented lipid antigens. However, peptide recognition in the context of CD1 has also been documented, although no self-peptide ligands have been reported to date. Here, we have identified an endogenous peptide that is presented by CD1d to activate mouse NKT cells. This peptide, the immunodominant epitope from mouse collagen type II (mCII707–721), was not associated with either MHC class I or II. Activation of CD1d-restricted mCII707–721–specific NKT cells was induced via TCR signaling and classical costimulation. In addition, mCII707–721–specific NKT cells induced T cell death through Fas/FasL, in an IL-17A–independent fashion. Moreover, mCII707–721–specific NKT cells suppressed a range of in vivo inflammatory conditions, including delayed-type hypersensitivity, antigen-induced airway inflammation, collagen-induced arthritis, and EAE, which were all ameliorated by mCII707-721 vaccination. The findings presented here offer new insight into the intrinsic roles of NKT cells in health and disease. Given the results, endogenous collagen peptide activators of NKT cells may offer promise as novel therapeutics in tissue-specific autoimmune and inflammatory diseases.
Yawei Liu, Anna Teige, Emma Mondoc, Saleh Ibrahim, Rikard Holmdahl, Shohreh Issazadeh-Navikas
Infection with influenza A virus represents a major public health threat worldwide, particularly in patients with asthma. However, immunity induced by influenza A virus may have beneficial effects, particularly in young children, that might protect against the later development of asthma, as suggested by the hygiene hypothesis. Herein, we show that infection of suckling mice with influenza A virus protected the mice as adults against allergen-induced airway hyperreactivity (AHR), a cardinal feature of asthma. The protective effect was associated with the preferential expansion of CD4–CD8–, but not CD4+, NKT cells and required T-bet and TLR7. Adoptive transfer of this cell population into allergen-sensitized adult mice suppressed the development of allergen-induced AHR, an effect associated with expansion of the allergen-specific forkhead box p3+ (Foxp3+) Treg cell population. Influenza-induced protection was mimicked by treating suckling mice with a glycolipid derived from Helicobacter pylori (a bacterium associated with protection against asthma) that activated NKT cells in a CD1d-restricted fashion. These findings suggest what we believe to be a novel pathway that can regulate AHR, and a new therapeutic strategy (treatment with glycolipid activators of this NKT cell population) for asthma.
Ya-Jen Chang, Hye Young Kim, Lee A. Albacker, Hyun Hee Lee, Nicole Baumgarth, Shizuo Akira, Paul B. Savage, Shin Endo, Takashi Yamamura, Janneke Maaskant, Naoki Kitano, Abel Singh, Apoorva Bhatt, Gurdyal S. Besra, Peter van den Elzen, Ben Appelmelk, Richard W. Franck, Guangwu Chen, Rosemarie H. DeKruyff, Michio Shimamura, Petr Illarionov, Dale T. Umetsu