The role of complement component C5 in asthma remains controversial. Here we examined the contribution of C5 at 3 critical checkpoints during the course of disease. Using an mAb specific for C5, we were able to evaluate the contribution of C5 during (a) the initiation of airway inflammation, (b) the maintenance of airway hyperresponsiveness (AHR), and (c) sustainment of an ongoing airway response to allergen provocation. Our results indicate that C5 is probably activated intrapulmonarily after infections or exposures to allergen and C5 inhibition has profound effects at all 3 critical checkpoints. In contrast to an earlier report, C5-deficient mice with established airway inflammation did not have elevated AHR to nonspecific stimuli. In the presence of airway inflammation, C5a serves as a direct link between the innate immune system and the development of AHR by engaging directly with its receptors expressed in airways. Through their powerful chemotactic and cell activation properties, both C5a and C5b-9 regulate the downstream inflammatory cascade, which results in a massive migration of inflammatory cells into the bronchial airway lumen and triggers the release of multiple harmful inflammatory mediators. This study suggests that targeting C5 is a potential clinical approach for treating patients with asthma.
Tao Peng, Liming Hao, Joseph A. Madri, Xiao Su, Jack A. Elias, Gregory L. Stahl, Stephen Squinto, Yi Wang
Th1 type cytokine responses are critical in the control of Mycobacterium tuberculosis infection. Recent findings indicate that 5-lipoxygenase–dependent (5-LO–dependent) lipoxins regulate host IL-12 production in vivo. Here, we establish lipoxins as key chemical mediators in resistance to M. tuberculosis infection. High levels of lipoxin A4 (LXA4) were detected in sera from infected WT but not infected 5-LO–deficient mice. Moreover, lungs from M. tuberculosis–infected 5-lo–/– animals showed increased IL-12, IFN-γ, and NO synthase 2 (NOS2) mRNA levels compared with the same tissues in WT mice. Similarly, splenocyte recall responses were enhanced in mycobacteria-infected 5-lo–/– versus WT mice. Importantly, bacterial burdens in 5-lo–/– lungs were significantly lower than those from WT mice, and this enhancement in the resistance of the 5-lo–/– animals to M. tuberculosis was completely prevented by administration of a stable LXA4 analog. Together our results demonstrate that lipoxins negatively regulate protective Th1 responses against mycobacterial infection in vivo and suggest that the inhibition of lipoxin biosynthesis could serve as a strategy for enhancing host resistance to M. tuberculosis.
Andre Bafica, Charles A. Scanga, Charles Serhan, Fabiana Machado, Sandy White, Alan Sher, Julio Aliberti
T cell differentiation is a progressive process characterized by phenotypic and functional changes. By transferring tumor-specific CD8+ T cells into tumor-bearing mice at various stages of differentiation, we evaluated their efficacy for adoptive immunotherapy. We found that administration of naive and early effector T cells, in combination with active immunization and IL-2, resulted in the eradication of large, established tumors. Despite enhanced in vitro antitumor properties, more-differentiated effector T cells were less effective for in vivo tumor treatment. Several events may underlie this paradoxical phenomenon: (a) downregulation of lymphoid-homing and costimulatory molecules; (b) inability to produce IL-2 and access homeostatic cytokines; and (c) entry into a proapoptotic and replicative senescent state. While the progressive acquisition of terminal effector properties is characterized by pronounced in vitro tumor killing, in vivo T cell activation, proliferation, and survival are progressively impaired. These findings suggest that the current methodology for selecting T cells for transfer is inadequate and provide new criteria for the generation and the screening of optimal lymphocyte populations for adoptive immunotherapy.
Luca Gattinoni, Christopher A. Klebanoff, Douglas C. Palmer, Claudia Wrzesinski, Keith Kerstann, Zhiya Yu, Steven E. Finkelstein, Marc R. Theoret, Steven A. Rosenberg, Nicholas P. Restifo
A specific hypoglycosylated isoform of the complement regulator membrane cofactor protein (MCP; CD46) is expressed on the inner acrosomal membrane (IAM) of spermatozoa. This membrane is exposed after the acrosome reaction, an exocytosis event that occurs upon contact with the zona pellucida. We initiated this investigation to assess MCP’s regulatory function in situ on spermatozoa. Upon exposure of human spermatozoa to autologous serum or follicular fluid, we unexpectedly observed that acrosome-reacted spermatozoa activated the complement cascade efficiently through C3 but not beyond. Using FACS to simultaneously evaluate viability, acrosomal status, and complement deposition, we found that complement activation was initiated by C-reactive protein (CRP) and was C1q, C2, and factor B dependent. This pattern is consistent with engagement of the classical pathway followed by amplification through the alternative pathway. C3b deposition was targeted to the IAM, where it was cleaved to C3bi. Factor H, and not MCP, was the cofactor responsible for C3b cleavage. We propose that this localized deposition of complement fragments aids in the fusion process between the spermatozoa and egg, in a role akin to that of complement in immune adherence. In addition, we speculate that this “targeted and restricted” form of complement activation on host cells is a common strategy to handle modified self.
Rebecca C. Riley-Vargas, Susan Lanzendorf, John P. Atkinson
CD4+CD25+ Tregs are important in the maintenance of immunological self tolerance and in the prevention of autoimmune diseases. As the CD4+CD25+ T cell population in patients with human T cell lymphotropic virus type I–associated (HTLV-I–associated) myelopathy/tropical spastic paraparesis (HAM/TSP) has been shown to be a major reservoir for this virus, it was of interest to determine whether the frequency and function of CD4+CD25+ Tregs in HAM/TSP patients might be affected. In these cells, both mRNA and protein expression of the forkhead transcription factor Foxp3, a specific marker of Tregs, were lower than those in CD4+CD25+ T cells from healthy individuals. The virus-encoded transactivating HTLV-I tax gene was demonstrated to have a direct inhibitory effect on Foxp3 expression and function of CD4+CD25+ T cells. This is the first report to our knowledge demonstrating the role of a specific viral gene product (HTLV-I Tax) on the expression of genes associated with Tregs (in particular, foxp3) resulting in inhibition of Treg function. These results suggest that direct human retroviral infection of CD4+CD25+ T cells may be associated with the pathogenesis of HTLV-I–associated neurologic disease.
Yoshihisa Yamano, Norihiro Takenouchi, Hong-Chuan Li, Utano Tomaru, Karen Yao, Christian W. Grant, Dragan A. Maric, Steven Jacobson
Aysefa Doganci, Tatjana Eigenbrod, Norbert Krug, George T. De Sanctis, Michael Hausding, Veit J. Erpenbeck, El-Bdaoui Haddad, Edgar Schmitt, Tobias Bopp, Karl-J. Kallen, Udo Herz, Steffen Schmitt, Cornelia Luft, Olaf Hecht, Jens M. Hohlfeld, Hiroaki Ito, Norihiro Nishimoto, Kazuyuki Yoshizaki, Tadamitsu Kishimoto, Stefan Rose-John, Harald Renz, Markus F. Neurath, Peter R. Galle, Susetta Finotto
X-linked lymphoproliferative disease (XLP) is an often-fatal immunodeficiency characterized by hypogammaglobulinemia, fulminant infectious mononucleosis, and/or lymphoma. The genetic lesion in XLP, SH2D1A, encodes the adaptor protein SAP (signaling lymphocytic activation molecule–associated [SLAM-associated] protein); however, the mechanism(s) by which mutations in SH2D1A causes hypogammaglobulinemia is unknown. Our analysis of 14 XLP patients revealed normal B cell development but a marked reduction in the number of memory B cells. The few memory cells detected were IgM+, revealing deficient isotype switching in vivo. However, XLP B cells underwent proliferation and differentiation in vitro as efficiently as control B cells, which indicates that the block in differentiation in vivo is B cell extrinsic. This possibility is supported by the finding that XLP CD4+ T cells did not efficiently differentiate into IL-10+ effector cells or provide optimal B cell help in vitro. Importantly, the B cell help provided by SAP-deficient CD4+ T cells was improved by provision of exogenous IL-10 or ectopic expression of SAP, which resulted in increased IL-10 production by T cells. XLP CD4+ T cells also failed to efficiently upregulate expression of inducible costimulator (ICOS), a potent inducer of IL-10 production by CD4+ T cells. Thus, insufficient IL-10 production may contribute to hypogammaglobulinemia in XLP. This finding suggests new strategies for treating this immunodeficiency.
Cindy S. Ma, Nathan J. Hare, Kim E. Nichols, Loic Dupré, Grazia Andolfi, Maria-Grazia Roncarolo, Stephen Adelstein, Philip D. Hodgkin, Stuart G. Tangye
Gaël Ménasché, Chen Hsuan Ho, Ozden Sanal, Jérôme Feldmann, Ilhan Tezcan, Fügen Ersoy, Anne Houdusse, Alain Fischer, Geneviève de Saint Basile
Kyoko Katakura, Jongdae Lee, Daniel Rachmilewitz, Gloria Li, Lars Eckmann, Eyal Raz
Experimental colitis is mediated by inflammatory or dysregulated immune responses to microbial factors of the gastrointestinal tract. In this study we observed that administration of Toll-like receptor 9 (TLR9) agonists suppressed the severity of experimental colitis in RAG1–/– but not in SCID mice. This differential responsiveness between phenotypically similar but genetically distinct animals was related to a partial blockade in TLR9 signaling and defective production of type I IFN (i.e., IFN-α/β) in SCID mice upon TLR9 stimulation. The addition of neutralization antibodies against type I IFN abolished the antiinflammatory effects induced by TLR9 agonists, whereas the administration of recombinant IFN-β mimicked the antiinflammatory effects induced by TLR9 agonists in this model. Furthermore, mice deficient in the IFN-α/β receptor exhibited more severe colitis than wild-type mice did upon induction of experimental colitis. These results indicate that TLR9-triggered type I IFN has antiinflammatory functions in colitis. They also underscore the important protective role of type I IFN in intestinal homeostasis and suggest that strategies to modulate innate immunity may be of therapeutic value for the treatment of intestinal inflammatory conditions.
Kyoko Katakura, Jongdae Lee, Daniel Rachmilewitz, Gloria Li, Lars Eckmann, Eyal Raz