- Email: [email protected]
Complement and IL-22: Partnering Up for Border Patrol
Immunity
Previews Deeks, S.G. (2011). Annu. Rev. Med. 62, 141–155. He, J., Tsai, L.M., Leong, Y.A., Hu, X., Ma, C.S., Chevalier, N., Sun, X., Vandenberg, K., Rockman, S., Ding, Y., et al. (2013). Immunity 39, 770–781. Hu, R., Kagele, D.A., Huffaker, T.B., Runtsch, M.C., Alexander, M., Liu, J., Bake, E., Su, W., Williams, M.A., Rao, D.S., et al. (2014). Immunity 41, this issue, 605–619.
Huffaker, T.B., Hu, R., Runtsch, M.C., Bake, E., Chen, X., Zhao, J., Round, J.L., Baltimore, D., and O’Connell, R.M. (2012). Cell Reports 2, 1697–1709. Lind, E.F., and Ohashi, P.S. (2014). Eur. J. Immunol. 44, 11–15. Ma, C.S., Deenick, E.K., Batten, M., and Tangye, S.G. (2012). J. Exp. Med. 209, 1241–1253.
Shen, N., Liang, D., Tang, Y., de Vries, N., and Tak, P.P. (2012). Nat Rev Rheumatol 8, 701–709. Yang, L., Boldin, M.P., Yu, Y., Liu, C.S., Ea, C.K., Ramakrishnan, P., Taganov, K.D., Zhao, J.L., and Baltimore, D. (2012). J. Exp. Med. 209, 1655–1670. Yu, D., Chen, Y., and Leong, Y.A. (2014). Nat. Immunol. 15, 597–599.
Complement and IL-22: Partnering Up for Border Patrol Hidekazu Yamamoto1 and Claudia Kemper1,* 1Division of Transplant Immunology and Mucosal Biology, MRC Centre for Transplantation, King’s College London, Guy’s Hospital, London SE1 9RT, UK *Correspondence: [email protected] http://dx.doi.org/10.1016/j.immuni.2014.10.002
Intestinal pathobionts that escape into the periphery can cause serious morbidity and death. In this issue of Immunity, Hasegawa et al. (2014) show that the host’s protective measures against such events include interleukin-22-driven systemic elimination of pathobionts via complement regulation. An extraordinary number and variety of microbes populate our gastrointestinal system. During evolution, the host and the gut microbiota establish a complex relationship that is now acknowledged as being well beyond mere coexistence such that it has an explicit mutualistic nature whereby the intestinal flora is often considered a microbial organ placed within the gut. The gut microbiota regulates host energy balance and mediates normal production of several vitamins and hormones as well as water adsorption. Moreover, intestinal bacteria are critically required for the development of gut-associated lymphoid organs and protect the host from colonization with invading harmful microbial species and pathogens throughout life. However, maintaining the integrity of the intestinal barrier and sustaining a homeostatic balance among the dynamic microbiota are key to health because the normal gut flora contains several potentially virulent species, called pathobionts, that can cause disease when they escape into the host’s periphery (Hasegawa et al., 2012). For example, the common treatment of hospitalized patients with broad-spectrum antibiotics results
in alterations of the normal intestinal microbiota and fosters overgrowth of pathogenic Gram-positive spore-forming Clostridium difficile, which is normally prevented by commensals. C. difficilederived toxins then damage the intestinal epithelium, which leads to translocation of intestinal bacteria into the extraintestinal space and causes infectious diarrhea and pseudomembranous colitis. Thus, C. difficile infection is a disease with a largely iatrogenic cause and with worrying rising incidence and increasing severity of pathogenesis: elimination of C. difficile with vancomycin and/or metronidazole is ineffective in about 4%–7% of patients, and C. difficile infection can be fatal specifically in the frail, elderly, or immunocompromised. Importantly, recent work in the field strongly indicates that commensals and/ or pathobionts that have breached the compromised epithelial barrier during C. difficile infection and accumulate in extraintestinal organs and tissues contribute to disease pathogenesis and mortality (Hasegawa et al., 2012). However, the underlying mechanisms supporting peripheral pathobiont dissemination and the measures taken by the
host’s immune system are unanswered questions. The current study by Hasegawa et al. (2014) delivers some important mechanistic insights into these complex events in C. difficile infection. The authors have examined the role of interleukin-22 (IL22) in C. difficile infection in protection against secondary pathobiont sepsis and survival. Using an established animal model, the study first observed strikingly lower survival rates in Il22 / mice than in wild-type control mice after C. difficile infection. This was shown to be associated with the translocation of ordinarily ‘‘commensal’’ bacteria (or pathobionts) of the predominant g-enterobacterial type to extraintestinal sites, such as the liver and lung, only in IL-22-deficient mice. These mice, however, could be rescued either by elimination of pathobionts by targeted antibiotics or through administration of recombinant IL-22. Although the central role of IL-22 in the prevention of pathobiont translocation has previously been acknowledged (Aujla et al., 2008; Basu et al., 2012; Sonnenberg et al., 2012), a novel mechanistic link between IL-22 and enhanced pathobiont killing was then elegantly identified by
Immunity 41, October 16, 2014 ª2014 Elsevier Inc. 511
Immunity
Previews
screening in Gene Expression Omnibus data sets for highly expressed genes in colonic tissue after IL-22 administration. This revealed that complement C3, a hub protein for activation of complement pathways, was among the most strongly IL-22-induced proteins. Subsequent in vitro and in vivo experiments with C3-deficient or -depleted animals, cells, and serum samples then allowed the authors to develop a model in which C. difficileinfection-induced generation of IL-22 provoked increased C3 production and secretion by the liver in a STAT3-dependent manner. This led to a substantial increase in systemic serum amounts of C3, which in turn mediated enhanced opsonization of translocated commensals and pathobionts via C3b and their killing and removal by neutrophils and macrophages (Figure 1). Thus, the authors demonstrate for the first time a critical role for IL-22 not only in host protection at the intestine but also in systemic clearance of pathobionts. Importantly, Hasegawa et al. (2014) demonstrated that individual strains of the translocated pathobionts displayed different sensitivities to C3b opsonization and complement-mediated uptake by neutrophils and that the acquisition of pathobiont complement resistance was the likely cause of their successful population of peripheral organs and the fatal complications in C. difficile infection. These findings might have clinical implications given that the mechanistic understanding of complement resistance in commensals and/or pathobionts could provide urgently needed novel treatment options to limit the severe pathogenesis observed in cases of uncontrolled C. difficile infection.
Figure 1. A Functional Axis between IL-22 and Complement Protects the Host from Systemic Pathobiont Dissemination after Damage to the Intestinal Border Dysbiosis in the gut can lead to uncontrolled C. difficile growth and subsequent intestinal epithelial damage by C. difficile-derived toxins. This allows translocation of commensals and pathobionts into the extra-
512 Immunity 41, October 16, 2014 ª2014 Elsevier Inc.
intestinal environment, which induces the local generation of IL-1b and IL-22 and recruitment and activation of neutrophils and other phagocytes that contain and remove bacteria. Pathobionts escaping further into the periphery are normally C3b opsonized and tagged for removal by an IL22-driven increase in systemic liver-derived C3 production. Phagocytic uptake and destruction of opsonized bacteria are then mediated by tissueresident and/or tissue-infiltrating neutrophils and macrophages (because complement activation induces recruitment of phagocytes into tissues). However, absent or reduced amounts of IL-22 generation (preventing the increase in protective systemic C3 amounts) and translocation of pathobionts resistant to complement-mediated phagocytic uptake can both lead to failure of pathobiont elimination in peripheral organs.
Immunity
Previews IL-22 is an evolutionarily old cytokine, and it seems plausible for a link to exist with the complement pathway, itself one of the oldest components of our immune system. Complement proteins are acute phase proteins that are dynamically regulated, especially at times of high consumption, such as sepsis. The evidence that induction of IL-22 subsequently leads to increases in C3 synthesis could be viewed as a counterbalancing mechanism to the increase in C3 consumption during C. difficile infection and pathobiont septicemia, and defining exactly how this occurs could be an interesting future study. The authors suggest that this novel functional axis between IL-22 and C3 could also be exploited therapeutically via the controlled modulation of IL-22 amounts. Indeed, although IL-22 is required for the clearance of certain pathogens (Aujla et al., 2008) and plays a central role in the maintenance of the epithelial barrier (Sonnenberg et al., 2012; Zheng et al., 2008) and in the initial establishment of host-microbiota symbiosis (Goto et al., 2014), it appears to have a rather modest direct impact on immune cells, and therefore modulation of IL-22 makes it less likely to induce the highly toxic side effects often seen in cytokine therapy. However, it is also apparent that the biology of IL-22 is not yet fully understood and explored and that this cytokine mediates strongly context-specific effects. For example, a recent study demonstrated that IL-22 tips the balance between pathogenic and commensal bacteria in favor of a pathogen and promotes Salmonella enterica serovar Typhimurium infection (Behnsen et al., 2014) and that circulating IL-22 mediates a strong acute phase response (Liang et al., 2010)—thus, further increasing IL22 in such settings could be detrimental. Furthermore, the cellular source of IL-22 also varies and depends on specific experimental settings and infection models. IL-22 is classically described as derived from activated T cells, and a recent study identified T helper 22 cells as the key IL-22 source for host protection against enteropathogenic bacteria
(Basu et al., 2012). IL-22 production by intestinal innate lymphoid and NKp46+ cells has also been described. On the other hand, in the current study by Hasegawa et al. (2014), tissue concentrations of IL-22 were still high in Rag1–/– mice, and the authors suggest that IL-22 is largely produced by neutrophils in their model (Hasegawa et al., 2014). Thus, defining the specific induction modes of IL-22 secretion by distinct cell populations in C. difficile and other infection models will be important. The novel connection between IL-22 and complement touches on another area of traditionally high interest for potential pharmacological modulation: because complement dysregulation contributes to many disease states, it has been under investigation for therapeutic targeting for decades. However, many of the attempts in controlling complement directly have been hampered by our slow understanding that complement, like IL-22 and many other cytokines and growth factors, is a functionally similarly ambiguous system. Complement is only recently being considered by the wider immunology community as having functions extending beyond protective immunity to include cell generative, degenerative, and regenerative processes. In addition, it is now emerging that the role of ‘‘classic’’ systemic liverderived complement is functionally different from locally or intracellularly generated and activated complement. Hasegawa et al. (2014) show here that C. difficile-infection-driven circulating IL22 induces an increase in C3 secretion by the liver, and they have focused on the role of hepatic systemic C3 induction during pathobiont and commensal clearance in the periphery. However, aside from hepatic C3 induction, the authors also observed that the addition of recombinant IL-22 induced C3 mRNA expression in other organs, including the spleen, lung, and intestines. Although this finding was not further functionally explored here, it aligns with our developing understanding that many, if not most, effector systems exert ‘‘location-specific’’ functions. Thus, a careful future analysis of nonhe-
patic induction of C3 production during C. difficile infection, specifically at the intestinal location where the epithelial barrier is breached and where commensal and/or pathobiont release induces an immediate local immune reaction, might unearth additional dimensions in this new functional partnership between IL22 and complement in pathobiont control. It could also potentially extend to barrier maintenance itself given that complement has been shown to promote intestinal wound healing (Cardone et al., 2011). In sum, the data presented in this work pave the way for future studies to explore and possibly exploit the exact mechanisms by which IL-22 and complement partner up for protective host environmental border patrol. REFERENCES Aujla, S.J., Chan, Y.R., Zheng, M., Fei, M., Askew, D.J., Pociask, D.A., Reinhart, T.A., McAllister, F., Edeal, J., Gaus, K., et al. (2008). Nat. Med. 14, 275–281. Basu, R., O’Quinn, D.B., Silberger, D.J., Schoeb, T.R., Fouser, L., Ouyang, W., Hatton, R.D., and Weaver, C.T. (2012). Immunity 37, 1061–1075. Behnsen, J., Jellbauer, S., Wong, C.P., Edwards, R.A., George, M.D., Ouyang, W., and Raffatellu, M. (2014). Immunity 40, 262–273. Cardone, J., Al-Shouli, S., and Kemper, C. (2011). Front. Immunol. 2, 28. Goto, Y., Obata, T., Kunisawa, J., Sato, S., Ivanov, I.I., Lamichhane, A., Takeyama, N., Kamioka, M., Sakamoto, M., Matsuki, T., et al. (2014). Science 345, 1254009. Hasegawa, M., Kamada, N., Jiao, Y., Liu, M.Z., Nu´n˜ez, G., and Inohara, N. (2012). J. Immunol. 189, 3085–3091. Hasegawa, M., Yada, S., Liu, M.Z., Kamada, N., Munoz-Planillo, R., Do, N., Nunez, G., and Inohara, N. (2014). Immunity 41, this issue, 620–632. Liang, S.C., Nickerson-Nutter, C., Pittman, D.D., Carrier, Y., Goodwin, D.G., Shields, K.M., Lambert, A.J., Schelling, S.H., Medley, Q.G., Ma, H.L., et al. (2010). J. Immunol. 185, 5531–5538. Sonnenberg, G.F., Monticelli, L.A., Alenghat, T., Fung, T.C., Hutnick, N.A., Kunisawa, J., Shibata, N., Grunberg, S., Sinha, R., Zahm, A.M., et al. (2012). Science 336, 1321–1325. Zheng, Y., Valdez, P.A., Danilenko, D.M., Hu, Y., Sa, S.M., Gong, Q., Abbas, A.R., Modrusan, Z., Ghilardi, N., de Sauvage, F.J., and Ouyang, W. (2008). Nat. Med. 14, 282–289.
Immunity 41, October 16, 2014 ª2014 Elsevier Inc. 513
Previews Deeks, S.G. (2011). Annu. Rev. Med. 62, 141–155. He, J., Tsai, L.M., Leong, Y.A., Hu, X., Ma, C.S., Chevalier, N., Sun, X., Vandenberg, K., Rockman, S., Ding, Y., et al. (2013). Immunity 39, 770–781. Hu, R., Kagele, D.A., Huffaker, T.B., Runtsch, M.C., Alexander, M., Liu, J., Bake, E., Su, W., Williams, M.A., Rao, D.S., et al. (2014). Immunity 41, this issue, 605–619.
Huffaker, T.B., Hu, R., Runtsch, M.C., Bake, E., Chen, X., Zhao, J., Round, J.L., Baltimore, D., and O’Connell, R.M. (2012). Cell Reports 2, 1697–1709. Lind, E.F., and Ohashi, P.S. (2014). Eur. J. Immunol. 44, 11–15. Ma, C.S., Deenick, E.K., Batten, M., and Tangye, S.G. (2012). J. Exp. Med. 209, 1241–1253.
Shen, N., Liang, D., Tang, Y., de Vries, N., and Tak, P.P. (2012). Nat Rev Rheumatol 8, 701–709. Yang, L., Boldin, M.P., Yu, Y., Liu, C.S., Ea, C.K., Ramakrishnan, P., Taganov, K.D., Zhao, J.L., and Baltimore, D. (2012). J. Exp. Med. 209, 1655–1670. Yu, D., Chen, Y., and Leong, Y.A. (2014). Nat. Immunol. 15, 597–599.
Complement and IL-22: Partnering Up for Border Patrol Hidekazu Yamamoto1 and Claudia Kemper1,* 1Division of Transplant Immunology and Mucosal Biology, MRC Centre for Transplantation, King’s College London, Guy’s Hospital, London SE1 9RT, UK *Correspondence: [email protected] http://dx.doi.org/10.1016/j.immuni.2014.10.002
Intestinal pathobionts that escape into the periphery can cause serious morbidity and death. In this issue of Immunity, Hasegawa et al. (2014) show that the host’s protective measures against such events include interleukin-22-driven systemic elimination of pathobionts via complement regulation. An extraordinary number and variety of microbes populate our gastrointestinal system. During evolution, the host and the gut microbiota establish a complex relationship that is now acknowledged as being well beyond mere coexistence such that it has an explicit mutualistic nature whereby the intestinal flora is often considered a microbial organ placed within the gut. The gut microbiota regulates host energy balance and mediates normal production of several vitamins and hormones as well as water adsorption. Moreover, intestinal bacteria are critically required for the development of gut-associated lymphoid organs and protect the host from colonization with invading harmful microbial species and pathogens throughout life. However, maintaining the integrity of the intestinal barrier and sustaining a homeostatic balance among the dynamic microbiota are key to health because the normal gut flora contains several potentially virulent species, called pathobionts, that can cause disease when they escape into the host’s periphery (Hasegawa et al., 2012). For example, the common treatment of hospitalized patients with broad-spectrum antibiotics results
in alterations of the normal intestinal microbiota and fosters overgrowth of pathogenic Gram-positive spore-forming Clostridium difficile, which is normally prevented by commensals. C. difficilederived toxins then damage the intestinal epithelium, which leads to translocation of intestinal bacteria into the extraintestinal space and causes infectious diarrhea and pseudomembranous colitis. Thus, C. difficile infection is a disease with a largely iatrogenic cause and with worrying rising incidence and increasing severity of pathogenesis: elimination of C. difficile with vancomycin and/or metronidazole is ineffective in about 4%–7% of patients, and C. difficile infection can be fatal specifically in the frail, elderly, or immunocompromised. Importantly, recent work in the field strongly indicates that commensals and/ or pathobionts that have breached the compromised epithelial barrier during C. difficile infection and accumulate in extraintestinal organs and tissues contribute to disease pathogenesis and mortality (Hasegawa et al., 2012). However, the underlying mechanisms supporting peripheral pathobiont dissemination and the measures taken by the
host’s immune system are unanswered questions. The current study by Hasegawa et al. (2014) delivers some important mechanistic insights into these complex events in C. difficile infection. The authors have examined the role of interleukin-22 (IL22) in C. difficile infection in protection against secondary pathobiont sepsis and survival. Using an established animal model, the study first observed strikingly lower survival rates in Il22 / mice than in wild-type control mice after C. difficile infection. This was shown to be associated with the translocation of ordinarily ‘‘commensal’’ bacteria (or pathobionts) of the predominant g-enterobacterial type to extraintestinal sites, such as the liver and lung, only in IL-22-deficient mice. These mice, however, could be rescued either by elimination of pathobionts by targeted antibiotics or through administration of recombinant IL-22. Although the central role of IL-22 in the prevention of pathobiont translocation has previously been acknowledged (Aujla et al., 2008; Basu et al., 2012; Sonnenberg et al., 2012), a novel mechanistic link between IL-22 and enhanced pathobiont killing was then elegantly identified by
Immunity 41, October 16, 2014 ª2014 Elsevier Inc. 511
Immunity
Previews
screening in Gene Expression Omnibus data sets for highly expressed genes in colonic tissue after IL-22 administration. This revealed that complement C3, a hub protein for activation of complement pathways, was among the most strongly IL-22-induced proteins. Subsequent in vitro and in vivo experiments with C3-deficient or -depleted animals, cells, and serum samples then allowed the authors to develop a model in which C. difficileinfection-induced generation of IL-22 provoked increased C3 production and secretion by the liver in a STAT3-dependent manner. This led to a substantial increase in systemic serum amounts of C3, which in turn mediated enhanced opsonization of translocated commensals and pathobionts via C3b and their killing and removal by neutrophils and macrophages (Figure 1). Thus, the authors demonstrate for the first time a critical role for IL-22 not only in host protection at the intestine but also in systemic clearance of pathobionts. Importantly, Hasegawa et al. (2014) demonstrated that individual strains of the translocated pathobionts displayed different sensitivities to C3b opsonization and complement-mediated uptake by neutrophils and that the acquisition of pathobiont complement resistance was the likely cause of their successful population of peripheral organs and the fatal complications in C. difficile infection. These findings might have clinical implications given that the mechanistic understanding of complement resistance in commensals and/or pathobionts could provide urgently needed novel treatment options to limit the severe pathogenesis observed in cases of uncontrolled C. difficile infection.
Figure 1. A Functional Axis between IL-22 and Complement Protects the Host from Systemic Pathobiont Dissemination after Damage to the Intestinal Border Dysbiosis in the gut can lead to uncontrolled C. difficile growth and subsequent intestinal epithelial damage by C. difficile-derived toxins. This allows translocation of commensals and pathobionts into the extra-
512 Immunity 41, October 16, 2014 ª2014 Elsevier Inc.
intestinal environment, which induces the local generation of IL-1b and IL-22 and recruitment and activation of neutrophils and other phagocytes that contain and remove bacteria. Pathobionts escaping further into the periphery are normally C3b opsonized and tagged for removal by an IL22-driven increase in systemic liver-derived C3 production. Phagocytic uptake and destruction of opsonized bacteria are then mediated by tissueresident and/or tissue-infiltrating neutrophils and macrophages (because complement activation induces recruitment of phagocytes into tissues). However, absent or reduced amounts of IL-22 generation (preventing the increase in protective systemic C3 amounts) and translocation of pathobionts resistant to complement-mediated phagocytic uptake can both lead to failure of pathobiont elimination in peripheral organs.
Immunity
Previews IL-22 is an evolutionarily old cytokine, and it seems plausible for a link to exist with the complement pathway, itself one of the oldest components of our immune system. Complement proteins are acute phase proteins that are dynamically regulated, especially at times of high consumption, such as sepsis. The evidence that induction of IL-22 subsequently leads to increases in C3 synthesis could be viewed as a counterbalancing mechanism to the increase in C3 consumption during C. difficile infection and pathobiont septicemia, and defining exactly how this occurs could be an interesting future study. The authors suggest that this novel functional axis between IL-22 and C3 could also be exploited therapeutically via the controlled modulation of IL-22 amounts. Indeed, although IL-22 is required for the clearance of certain pathogens (Aujla et al., 2008) and plays a central role in the maintenance of the epithelial barrier (Sonnenberg et al., 2012; Zheng et al., 2008) and in the initial establishment of host-microbiota symbiosis (Goto et al., 2014), it appears to have a rather modest direct impact on immune cells, and therefore modulation of IL-22 makes it less likely to induce the highly toxic side effects often seen in cytokine therapy. However, it is also apparent that the biology of IL-22 is not yet fully understood and explored and that this cytokine mediates strongly context-specific effects. For example, a recent study demonstrated that IL-22 tips the balance between pathogenic and commensal bacteria in favor of a pathogen and promotes Salmonella enterica serovar Typhimurium infection (Behnsen et al., 2014) and that circulating IL-22 mediates a strong acute phase response (Liang et al., 2010)—thus, further increasing IL22 in such settings could be detrimental. Furthermore, the cellular source of IL-22 also varies and depends on specific experimental settings and infection models. IL-22 is classically described as derived from activated T cells, and a recent study identified T helper 22 cells as the key IL-22 source for host protection against enteropathogenic bacteria
(Basu et al., 2012). IL-22 production by intestinal innate lymphoid and NKp46+ cells has also been described. On the other hand, in the current study by Hasegawa et al. (2014), tissue concentrations of IL-22 were still high in Rag1–/– mice, and the authors suggest that IL-22 is largely produced by neutrophils in their model (Hasegawa et al., 2014). Thus, defining the specific induction modes of IL-22 secretion by distinct cell populations in C. difficile and other infection models will be important. The novel connection between IL-22 and complement touches on another area of traditionally high interest for potential pharmacological modulation: because complement dysregulation contributes to many disease states, it has been under investigation for therapeutic targeting for decades. However, many of the attempts in controlling complement directly have been hampered by our slow understanding that complement, like IL-22 and many other cytokines and growth factors, is a functionally similarly ambiguous system. Complement is only recently being considered by the wider immunology community as having functions extending beyond protective immunity to include cell generative, degenerative, and regenerative processes. In addition, it is now emerging that the role of ‘‘classic’’ systemic liverderived complement is functionally different from locally or intracellularly generated and activated complement. Hasegawa et al. (2014) show here that C. difficile-infection-driven circulating IL22 induces an increase in C3 secretion by the liver, and they have focused on the role of hepatic systemic C3 induction during pathobiont and commensal clearance in the periphery. However, aside from hepatic C3 induction, the authors also observed that the addition of recombinant IL-22 induced C3 mRNA expression in other organs, including the spleen, lung, and intestines. Although this finding was not further functionally explored here, it aligns with our developing understanding that many, if not most, effector systems exert ‘‘location-specific’’ functions. Thus, a careful future analysis of nonhe-
patic induction of C3 production during C. difficile infection, specifically at the intestinal location where the epithelial barrier is breached and where commensal and/or pathobiont release induces an immediate local immune reaction, might unearth additional dimensions in this new functional partnership between IL22 and complement in pathobiont control. It could also potentially extend to barrier maintenance itself given that complement has been shown to promote intestinal wound healing (Cardone et al., 2011). In sum, the data presented in this work pave the way for future studies to explore and possibly exploit the exact mechanisms by which IL-22 and complement partner up for protective host environmental border patrol. REFERENCES Aujla, S.J., Chan, Y.R., Zheng, M., Fei, M., Askew, D.J., Pociask, D.A., Reinhart, T.A., McAllister, F., Edeal, J., Gaus, K., et al. (2008). Nat. Med. 14, 275–281. Basu, R., O’Quinn, D.B., Silberger, D.J., Schoeb, T.R., Fouser, L., Ouyang, W., Hatton, R.D., and Weaver, C.T. (2012). Immunity 37, 1061–1075. Behnsen, J., Jellbauer, S., Wong, C.P., Edwards, R.A., George, M.D., Ouyang, W., and Raffatellu, M. (2014). Immunity 40, 262–273. Cardone, J., Al-Shouli, S., and Kemper, C. (2011). Front. Immunol. 2, 28. Goto, Y., Obata, T., Kunisawa, J., Sato, S., Ivanov, I.I., Lamichhane, A., Takeyama, N., Kamioka, M., Sakamoto, M., Matsuki, T., et al. (2014). Science 345, 1254009. Hasegawa, M., Kamada, N., Jiao, Y., Liu, M.Z., Nu´n˜ez, G., and Inohara, N. (2012). J. Immunol. 189, 3085–3091. Hasegawa, M., Yada, S., Liu, M.Z., Kamada, N., Munoz-Planillo, R., Do, N., Nunez, G., and Inohara, N. (2014). Immunity 41, this issue, 620–632. Liang, S.C., Nickerson-Nutter, C., Pittman, D.D., Carrier, Y., Goodwin, D.G., Shields, K.M., Lambert, A.J., Schelling, S.H., Medley, Q.G., Ma, H.L., et al. (2010). J. Immunol. 185, 5531–5538. Sonnenberg, G.F., Monticelli, L.A., Alenghat, T., Fung, T.C., Hutnick, N.A., Kunisawa, J., Shibata, N., Grunberg, S., Sinha, R., Zahm, A.M., et al. (2012). Science 336, 1321–1325. Zheng, Y., Valdez, P.A., Danilenko, D.M., Hu, Y., Sa, S.M., Gong, Q., Abbas, A.R., Modrusan, Z., Ghilardi, N., de Sauvage, F.J., and Ouyang, W. (2008). Nat. Med. 14, 282–289.
Immunity 41, October 16, 2014 ª2014 Elsevier Inc. 513