Expression of APOBEC family members as regulators of endogenous retroelements and malignant transformation in systemic autoimmunity.

OBJECTIVE: To explore whether APOBEC family members are involved in the response to inappropriate expression of L1 retroelements in primary Sjögren's syndrome (SS) and systemic lupus erythematosus (SLE), as well as in SS related lymphomagenesis. METHODS: Minor salivary glands (MSG) and kidney biopsy (KB) specimens were obtained from 41 SS patients (10 with lymphoma) and 23 patients with SLE, respectively. PBMC and sera were also collected from 73 SLE patients. Full-length L1 transcripts, members of the APOBEC and IFN family were quantitated by real time PCR. Type I IFN activity was assessed in lupus plasma by a cell assay. RESULTS: APOBEC3A was increased in SS MSG, SLE KB and PBMC and correlated with L1. AID and APOBEC3G were particularly overexpressed in MSG tissues derived from SS lymphoma patients. CONCLUSION: These data reveal a previously unappreciated role of APOBEC family proteins in the pathogenesis of systemic autoimmunity and SS related lymphomagenesis.

Secretory leukocyte protease inhibitor gene deletion alters bleomycin-induced lung injury, but not development of pulmonary fibrosis.

Idiopathic pulmonary fibrosis is a progressive, fatal disease with limited treatment options. Protease-mediated transforming growth factor-ß (TGF-ß) activation has been proposed as a pathogenic mechanism of lung fibrosis. Protease activity in the lung is tightly regulated by protease inhibitors, particularly secretory leukocyte protease inhibitor (SLPI). The bleomycin model of lung fibrosis was used to determine the effect of increased protease activity in the lungs of Slpi(-/-) mice following injury. Slpi(-/-), and wild-type, mice received oropharyngeal administration of bleomycin (30 IU) and the development of pulmonary fibrosis was assessed. Pro and active forms of matrix metalloproteinase (MMP)-2 and MMP-9 were measured. Lung fibrosis was determined by collagen subtype-specific gene expression, hydroxyproline concentration, and histological assessment. Alveolar TGF-ß activation was measured using bronchoalveolar lavage cell pSmad2 levels and global TGF-ß activity was assessed by pSmad2 immunohistochemistry. The active-MMP-9 to pro-MMP-9 ratio was significantly increased in Slpi(-/-) animals compared with wild-type animals, demonstrating enhanced metalloproteinase activity. Wild-type animals showed an increase in TGF-ß activation following bleomycin, with a progressive and sustained increase in collagen type I, alpha 1 (Col1α1), III, alpha 1(Col3α1), IV, alpha 1(Col4α1) mRNA expression, and a significant increase in total lung collagen 28 days post bleomycin. In contrast Slpi(-/-) mice showed no significant increase of alveolar TGF-ß activity following bleomycin, above their already elevated levels, although global TGF-ß activity did increase. Slpi(-/-) mice had impaired collagen gene expression but animals demonstrated minimal reduction in lung fibrosis compared with wild-type animals. These data suggest that enhanced proteolysis does not further enhance TGF-ß activation, and inhibits sustained Col1α1, Col3α1, and Col4α1 gene expression following lung injury. However, these changes do not prevent the development of lung fibrosis. Overall, these data suggest that the absence of Slpi does not markedly modify the development of lung fibrosis following bleomycin-induced lung injury.

Cellular immune activation in cerebrospinal fluid from ugandans with cryptococcal meningitis and immune reconstitution inflammatory syndrome.

BACKGROUND: Human immunodeficiency virus (HIV)-associated cryptococcal meningitis (CM) is characterized by high fungal burden and limited leukocyte trafficking to cerebrospinal fluid (CSF). The immunopathogenesis of CM immune reconstitution inflammatory syndrome (IRIS) after initiation of antiretroviral therapy at the site of infection is poorly understood. METHODS: We characterized the lineage and activation status of mononuclear cells in blood and CSF of HIV-infected patients with noncryptococcal meningitis (NCM) (n = 10), those with CM at day 0 (n = 40) or day 14 (n = 21) of antifungal therapy, and those with CM-IRIS (n = 10). RESULTS: At diagnosis, highly activated CD8(+) T cells predominated in CSF in both CM and NCM. CM-IRIS was associated with an increasing frequency of CSF CD4(+) T cells (increased from 2.2% to 23%; P = .06), a shift in monocyte phenotype from classic to an intermediate/proinflammatory, and increased programmed death ligand 1 expression on natural killer cells (increased from 11.9% to 61.6%, P = .03). CSF cellular responses were distinct from responses in peripheral blood. CONCLUSIONS: After CM, T cells in CSF tend to evolve with the development of IRIS, with increasing proportions of activated CD4(+) T cells, migration of intermediate monocytes to the CSF, and declining fungal burden. These changes provide insight into IRIS pathogenesis and could be exploited to more effectively treat CM and prevent CM-IRIS.

A link between interferon and augmented plasmin generation in exocrine gland damage in Sjögren's syndrome.

Sjögren's syndrome is an autoimmune disease that targets exocrine glands, but often exhibits systemic manifestations. Infiltration of the salivary and lacrimal glands by lymphoid and myeloid cells orchestrates a perpetuating immune response leading to exocrine gland damage and dysfunction. Th1 and Th17 lymphocyte populations and their products recruit additional lymphocytes, including B cells, but also large numbers of macrophages, which accumulate with disease progression. In addition to cytokines, chemokines, chitinases, and lipid mediators, macrophages contribute to a proteolytic milieu, underlying tissue destruction, inappropriate repair, and compromised glandular functions. Among the proteases enhanced in this local environment are matrix metalloproteases (MMP) and plasmin, generated by plasminogen activation, dependent upon plasminogen activators, such as tissue plasminogen activator (tPA). Not previously associated with salivary gland pathology, our evidence implicates enhanced tPA in the context of inflamed salivary glands revolving around lymphocyte-mediated activation of macrophages. Tracking down the mechanism of macrophage plasmin activation, the cytokines IFNγ and to a lesser extent, IFNα, via Janus kinase (JAK) and signal transducer and activator of transcription (STAT) activation, were found to be pivotal for driving the plasmin cascade of proteolytic events culminating in perpetuation of the inflammation and tissue damage, and suggesting intervention strategies to blunt irreversible tissue destruction.

Structural variants of IFNα preferentially promote antiviral functions.

IFNα, a cytokine with multiple functions in innate and adaptive immunity and a potent inhibitor of HIV, exerts antiviral activity, in part, by enhancing apolipoprotein B mRNA-editing enzyme-catalytic polypeptide-like 3 (APOBEC3) family members. Although IFNα therapy is associated with reduced viral burden, this cytokine also mediates immune dysfunction and toxicities. Through detailed mapping of IFNα receptor binding sites, we generated IFNα hybrids and mutants and determined that structural changes in the C-helix alter the ability of IFN to limit retroviral activity. Selective IFNα constructs differentially block HIV replication and their directional magnitude of inhibition correlates with APOBEC3 levels. Importantly, certain mutants exhibited reduced toxicity as reflected by induced indoleamine 2,3-dioxygenase (IDO), suggesting discreet and shared intracellular signaling pathways. Defining IFN structure and function relative to APOBEC and other antiviral genes may enable design of novel IFN-related molecules preserving beneficial antiviral roles while minimizing negative effects.

Modulation of innate host factors by Mycobacterium avium complex in human macrophages includes interleukin 17.

BACKGROUND: Although opportunistic infections due to Mycobacterium avium complex (MAC) have been less common since the introduction of highly active antiretroviral therapy, globally, human immunodeficiency virus-1 (HIV-1)-positive patients remain predisposed to these infections. Absence of a properly functioning acquired immune response allows MAC persistence within macrophages localized in lymph nodes coinfected with HIV and MAC. Although a deficiency in interferon γ appears to play a part in the ability of MAC to deflect the macrophage-associated antimicrobial attack, questions about this process remain. Our study examines the ability of MAC to regulate interleukin 17 (IL-17), a proinflammatory cytokine involved in host cell recruitment. METHODS: Coinfected lymph nodes were examined for IL-17 by immunohistochemical analysis. In vitro, macrophages exposed to mycobacteria were evaluated for transcription activities, proteins, and signaling pathways responsible for IL-17 expression. Infected macrophages were also analyzed for expression of interleukin 21 (IL-21) and negative regulators of immune responses. RESULTS: Infection of macrophages triggered synthesis of IL-17, correlating with IL-17 expression by macrophages in coinfected lymph nodes. Infected macrophages exposed to exogenous IL-17 expressed CXCL10, which favors recruitment of new macrophages as targets for infection. Blockade of nuclear factor κ-light-chain-enhancer of activated B cells and mitogen-activated protein kinase pathways suppressed mycobacteria-induced IL-17 expression. MAC triggered expression of IL-21, IRF4, and STAT3 genes related to IL-17 regulation, as well as expression of the negative immunoregulators CD274(PD-L1) and suppressors of cytokine signaling. CONCLUSIONS: MAC-infected macrophages can provide an alternative source for IL-17 that favors accumulation of new targets for perpetuating bacterial and viral infection while suppressing host antimicrobial immune responses.

Host gene expression changes correlating with anti-HIV-1 effects in human subjects after treatment with peginterferon Alfa-2a.

We investigated whether interferon-inducible genes (IFIGs) with known anti-human immunodeficiency virus (HIV) activity in vitro were associated with in vivo virological response in HIV infection. Nine untreated HIV-1-infected volunteers were treated for 12 weeks with peginterferon alfa-2a. A subset of IFIGs (23 of 47) increased compared with baseline through 6 weeks beyond therapy, and 10 of the 23 IFIGs significantly inversely correlated (r = -0.7; P < .05) with virological response. The strength of peginterferon alfa-2a-induced IFIG response significantly correlated with declines in HIV load during treatment (r(2) = 0.87, p = .003). This study links HIV virological response to a specific IFIG subset, a potential prognostic indicator in peginterferon alfa-2a-treated patients with HIV infection.

Induction of APOBEC3 family proteins, a defensive maneuver underlying interferon-induced anti-HIV-1 activity.

Apolipoprotein B mRNA-editing enzyme-catalytic polypeptide-like 3G (APOBEC3G), a cytidine deaminase, is a recently recognized innate intracellular protein with lethal activity against human immunodeficiency virus (HIV). Packaged into progeny virions, APOBEC3G enzymatic activity leads to HIV DNA degradation. As a counterattack, HIV virion infectivity factor (Vif) targets APOBEC3G for proteasomal proteolysis to exclude it from budding virions. Based on the ability of APOBEC3G to antagonize HIV infection, considerable interest hinges on elucidating its mechanism(s) of regulation. In this study, we provide the first evidence that an innate, endogenous host defense factor has the potential to promote APOBEC3G and rebuke the virus-mediated attempt to control its cellular host. We identify interferon (IFN)-alpha as a potent inducer of APOBEC3G to override HIV Vif neutralization of APOBEC3 proteins that pose a threat to efficient macrophage HIV replication. Our data provide a new dimension by which IFN-alpha mediates its antiviral activity and suggest a means to render the host nonpermissive for viral replication.

Secretory leukocyte protease inhibitor (SLPI) expression and tumor invasion in oral squamous cell carcinoma.

Differential expression of secretory leukocyte protease inhibitor (SLPI) impacts on tumor progression. SLPI directly inhibits elastase and other serine proteases, and regulates matrix metalloproteinases, plasminogen activation, and plasmin downstream targets to influence invasion. We examined tissues from human oral squamous cell carcinoma (OSCC) for SLPI expression in parallel with proteases associated with tumor progression and evaluated their relationships using tumor cell lines. Significantly decreased SLPI was detected in OSCC compared to normal oral epithelium. Furthermore, an inverse correlation between SLPI and histological parameters associated with tumor progression, including stage of invasion, pattern of invasion, invasive cell grade, and composite histological tumor score was evident. Conversely, elevated plasmin and elastase were positively correlated with histological parameters of tumor invasion. In addition to its known inhibition of elastase, we identify SLPI as a novel inhibitor of plasminogen activation through its interaction with annexin A2 with concomitant reduced plasmin generation by macrophages and OSCC cell lines. In an in vitro assay measuring invasive activity, SLPI blocked protease-dependent tumor cell migration. Our data suggest that SLPI may possess antitumorigenic activity by virtue of its ability to interfere with multiple requisite proteolytic steps underlying tumor cell invasion and may provide insight into potential stratification of oral cancer according to risk of occult metastasis, guiding treatment strategies.

Porphyromonas gingivalis promotes Th17 inducing pathways in chronic periodontitis.

In periodontitis, a common chronic inflammatory condition, gram-negative-rich bacterial biofilms trigger, in susceptible individuals, perpetuating inflammation that results in extensive tissue damage of tooth supporting structures. To delineate immune cell-dependent mechanisms whereby bacterial challenge drives persistent destructive inflammation in periodontitis and other inflammatory diseases, we studied involved tissues ex vivo and investigated host cell responses to the periodontal pathogen Porphyromonas gingivalis, in vitro. Diseased lesions were populated by abundant Th17 cells, linked to infection, chronic inflammation/autoimmunity and tissue pathology. In vitro, P. gingivalis, particularly the more virulent strain W83, stimulated myeloid antigen presenting cells (APC) to drive Th17 polarization. Supernatants from myeloid APC exposed to P. gingivalis were capable of enhancing Th17 but not Th1 polarization. P. gingivalis favored the generation of Th17 responses by stimulating the production of Th17 related cytokines IL-1ß, IL-6 and IL-23, but not Th1 related IL-12. By inducing NFκB activation, P. gingivalis promoted IL-1ß, IL-6 and IL-12p40 production, but not IRF3 phosphorylation, connected to generation of the IL-12p35 chain, ultimately restricting formation of the intact IL-12 molecule. Promotion of Th17 lineage responses was also aided by P. gingivalis proteases, which appeared to differentially degrade pivotal cytokines. In this regard, IL-12 was largely degraded by P. gingivalis, whereas IL-1ß was more resistant to proteolysis. Our data unveil multiple pathways by which P. gingivalis may orchestrate chronic inflammation, providing insights into interventional strategies.

Tumor necrosis factor-alpha (TNF-α) is a therapeutic target for impaired cutaneous wound healing.

Impaired wound healing states lead to substantial morbidity and cost with treatment resulting in an expenditure of billions of dollars per annum in the U.S. alone. Both chronic wounds and impaired acute wounds are characterized by excessive inflammation, enhanced proteolysis, and reduced matrix deposition. These confounding factors are exacerbated in the elderly, in part, as we report here, related to increased local and systemic tumor necrosis factor-alpha (TNF-α) levels. Moreover, we have used a secretory leukocyte protease inhibitor (SLPI) null mouse model of severely impaired wound healing and excessive inflammation, comparable to age-related delayed human healing, to demonstrate that topical application of anti-TNF-α neutralizing antibodies blunts leukocyte recruitment and NFκB activation, alters the balance between M1 and M2 macrophages, and accelerates wound healing. Following antagonism of TNF-α, matrix synthesis is enhanced, associated with suppression of both inflammatory parameters and NFκB binding activity. Our data suggest that inhibiting TNF-α is a critical event in reversing the severely impaired healing response associated with the absence of SLPI, and may be applicable to prophylaxis and/or treatment of impaired wound healing states in humans.

Chitinases in the salivary glands and circulation of patients with Sjögren's syndrome: macrophage harbingers of disease severity.

OBJECTIVE: Sjögren's syndrome (SS) is a chronic autoimmune disease of unknown etiology that targets salivary and lacrimal glands and may be accompanied by multiorgan systemic manifestations. To further the understanding of immunopathology associated with SS and identify potential therapeutic targets, we undertook the present study comparing the gene expression profiles of salivary glands with severe inflammation versus those of salivary glands with mild or no disease. METHODS: Using microarray profiling of salivary gland tissue from patients with SS and control subjects, we identified target genes, which were further characterized in tissue, serum, and cultured cell populations by real-time polymerase chain reaction and protein analysis. RESULTS: Among the most highly expressed SS genes were those associated with myeloid cells, including members of the mammalian chitinase family, which had not previously been shown to be associated with exocrinopathies. Both chitinase 3-like protein 1 and chitinase 1, highly conserved chitinase-like glycoproteins (one with enzymatic activity and one lacking enzymatic activity), were evident at the transcriptome level and were detected within inflamed tissue. Chitinases were expressed during monocyte-to-macrophage differentiation and their levels augmented by stimulation with cytokines, including interferon-α (IFNα). CONCLUSION: Because elevated expression of these and other macrophage-derived molecules corresponded with more severe SS, the present observations suggest that macrophages have potential immunopathologic involvement in SS and that the tissue macrophage transcription profile reflects multiple genes induced by IFNα.

Transforming growth factor-beta induces development of the T(H)17 lineage.

A new lineage of effector CD4+ T cells characterized by production of interleukin (IL)-17, the T-helper-17 (T(H)17) lineage, was recently described based on developmental and functional features distinct from those of classical T(H)1 and T(H)2 lineages. Like T(H)1 and T(H)2, T(H)17 cells almost certainly evolved to provide adaptive immunity tailored to specific classes of pathogens, such as extracellular bacteria. Aberrant T(H)17 responses have been implicated in a growing list of autoimmune disorders. T(H)17 development has been linked to IL-23, an IL-12 cytokine family member that shares with IL-12 a common subunit, IL-12p40 (ref. 8). The IL-23 and IL-12 receptors also share a subunit, IL-12Rbeta1, that pairs with unique, inducible components, IL-23R and IL-12Rbeta2, to confer receptor responsiveness. Here we identify transforming growth factor-beta (TGF-beta) as a cytokine critical for commitment to T(H)17 development. TGF-beta acts to upregulate IL-23R expression, thereby conferring responsiveness to IL-23. Although dispensable for the development of IL-17-producing T cells in vitro and in vivo, IL-23 is required for host protection against a bacterial pathogen, Citrobacter rodentium. The action of TGF-beta on naive T cells is antagonized by interferon-gamma and IL-4, thus providing a mechanism for divergence of the T(H)1, T(H)2 and T(H)17 lineages.

TGF-beta and tumors--an ill-fated alliance.

Mechanisms of host defense can form an unwitting alliance with tumor cells to promote tumor progression, invasion, and dissemination to distant sites. By secreting TGF-beta, an immunoregulatory molecule designated for both promoting inflammation and dampening immune responses, the tumor tricks the host into supporting its expansion and survival. TGF-beta not only recruits leukocytes to secrete chemokines, growth factors, cytokines, and proteases in support of a tumor-friendly niche but also in a context-specific manner, incapacitates the emergent immune response. As a profound immunosuppressant, TGF-beta, both directly and through the generation of regulatory T cells, blunts immune surveillance, favoring tumor escape. Collectively, the ability of the tumor to hijack these host defense pathways can tip the balance in favor of the tumor.

Interleukin-27 inhibition of HIV-1 involves an intermediate induction of type I interferon.

Infection of CD4(+) chemokine coreceptor(+) targets by HIV is aided and abetted by the proficiency of HIV in eliminating or neutralizing host cell-derived defensive molecules. Among these innate protective molecules, a family of intracellular apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like (APOBEC) cytidine deaminases, is constitutively expressed but inactivated by HIV viral infectivity factor. The ability of interferon-alpha (IFN-alpha) to augment cytidine deaminases offered the possibility that the balance between virus and target cell might be altered in favor of the host. Further characterization of transcriptional profiles induced by IFN-alpha using microarrays, with the intention to identify and dissociate retroviral countermaneuvers from associated toxicities, revealed multiple molecules with suspected antiviral activity, including IL-27. To establish whether IFN-alpha toxicity might be sidestepped through the use of downstream IL-27 against HIV, we examined whether IL-27 directly regulated cytidine deaminases. Although IL-27 induces APOBECs, it does so in a delayed fashion. Dissecting the underlying regulatory events uncovered an initial IL-27-dependent induction of IFN-alpha and/or IFN-beta, which in turn, induces APOBEC3, inhibited by IFN-alpha/beta receptor blockade. In addition to macrophages, the IL-27-IFN-alpha connection is operative in CD4(+) T cells, consistent with an IFN-alpha-dependent pathway underlying host cell defense to HIV.

Safety, tolerability, and mechanisms of antiretroviral activity of pegylated interferon Alfa-2a in HIV-1-monoinfected participants: a phase II clinical trial.

BACKGROUND: To our knowledge, the antiviral activity of pegylated interferon alfa-2a has not been studied in participants with untreated human immunodeficiency virus type 1 (HIV-1) infection but without chronic hepatitis C virus (HCV) infection. METHODS: Untreated HIV-1-infected volunteers without HCV infection received 180 microg of pegylated interferon alfa-2a weekly for 12 weeks. Changes in plasma HIV-1 RNA load, CD4(+) T cell counts, pharmacokinetics, pharmacodynamic measurements of 2',5'-oligoadenylate synthetase (OAS) activity, and induction levels of interferon-inducible genes (IFIGs) were measured. Nonparametric statistical analysis was performed. RESULTS: Eleven participants completed 12 weeks of therapy. The median plasma viral load decrease and change in CD4(+) T cell counts at week 12 were 0.61 log(10) copies/mL (90% confidence interval [CI], 0.20-1.18 log(10) copies/mL) and -44 cells/microL (90% CI, -95 to 85 cells/microL), respectively. There was no correlation between plasma viral load decreases and concurrent pegylated interferon plasma concentrations. However, participants with larger increases in OAS level exhibited greater decreases in plasma viral load at weeks 1 and 2 (r = -0.75 [90% CI, -0.93 to -0.28] and r = -0.61 [90% CI, -0.87 to -0.09], respectively; estimated Spearman rank correlation). Participants with higher baseline IFIG levels had smaller week 12 decreases in plasma viral load (0.66 log(10) copies/mL [90% CI, 0.06-0.91 log(10) copies/mL]), whereas those with larger IFIG induction levels exhibited larger decreases in plasma viral load (-0.74 log(10) copies/mL [90% CI, -0.93 to -0.21 log(10) copies/mL]). CONCLUSION: Pegylated interferon alfa-2a was well tolerated and exhibited statistically significant anti-HIV-1 activity in HIV-1-monoinfected patients. The anti-HIV-1 effect correlated with OAS protein levels (weeks 1 and 2) and IFIG induction levels (week 12) but not with pegylated interferon concentrations.

Conversion of peripheral CD4+CD25- naive T cells to CD4+CD25+ regulatory T cells by TGF-beta induction of transcription factor Foxp3.

CD4+CD25+ regulatory T cells (Treg) are instrumental in the maintenance of immunological tolerance. One critical question is whether Treg can only be generated in the thymus or can differentiate from peripheral CD4+CD25- naive T cells. In this paper, we present novel evidence that conversion of naive peripheral CD4+CD25- T cells into anergic/suppressor cells that are CD25+, CD45RB-/low and intracellular CTLA-4+ can be achieved through costimulation with T cell receptors (TCRs) and transforming growth factor beta (TGF-beta). Although transcription factor Foxp3 has been shown recently to be associated with the development of Treg, the physiological inducers for Foxp3 gene expression remain a mystery. TGF-beta induced Foxp3 gene expression in TCR-challenged CD4+CD25- naive T cells, which mediated their transition toward a regulatory T cell phenotype with potent immunosuppressive potential. These converted anergic/suppressor cells are not only unresponsive to TCR stimulation and produce neither T helper cell 1 nor T helper cell 2 cytokines but they also express TGF-beta and inhibit normal T cell proliferation in vitro. More importantly, in an ovalbumin peptide TCR transgenic adoptive transfer model, TGF-beta-converted transgenic CD4+CD25+ suppressor cells proliferated in response to immunization and inhibited antigen-specific naive CD4+ T cell expansion in vivo. Finally, in a murine asthma model, coadministration of these TGF-beta-induced suppressor T cells prevented house dust mite-induced allergic pathogenesis in lungs.

Secretory leukocyte protease inhibitor binds to annexin II, a cofactor for macrophage HIV-1 infection.

The distribution of secretory leukocyte protease inhibitor (SLPI) at entry portals indicates its involvement in defending the host from pathogens, consistent with the ability of SLPI to inhibit human immunodeficiency virus (HIV)-1 infection by an unknown mechanism. We now demonstrate that SLPI binds to the membrane of human macrophages through the phospholipid-binding protein, annexin II. Based on the recent identification of human cell membrane phosphatidylserine (PS) in the outer coat of HIV-1, we define a novel role for annexin II, a PS-binding moiety, as a cellular cofactor supporting macrophage HIV-1 infection. Moreover, this HIV-1 PS interaction with annexin II can be disrupted by SLPI or other annexin II-specific inhibitors. The PS-annexin II connection may represent a new target to prevent HIV-1 infection.

Transforming growth factor-beta production and myeloid cells are an effector mechanism through which CD1d-restricted T cells block cytotoxic T lymphocyte-mediated tumor immunosurveillance: abrogation prevents tumor recurrence.

Our previous work demonstrated that cytotoxic T lymphocyte (CTL)-mediated tumor immunosurveillance of the 15-12RM tumor could be suppressed by a CD1d-restricted lymphocyte, most likely a natural killer (NK) T cell, which produces interleukin (IL)-13. Here we present evidence for the effector elements in this suppressive pathway. T cell-reconstituted recombination activating gene (RAG)2 knockout (KO) and RAG2/IL-4 receptor alpha double KO mice showed that inhibition of immunosurveillance requires IL-13 responsiveness by a non-T non-B cell. Such nonlymphoid splenocytes from tumor-bearing mice produced more transforming growth factor (TGF)-beta, a potent inhibitor of CTL, ex vivo than such cells from naive mice, and this TGF-beta production was dependent on the presence in vivo of both IL-13 and CD1d-restricted T cells. Ex vivo TGF-beta production was also abrogated by depleting either CD11b+ or Gr-1+ cells from the nonlymphoid cells of tumor-bearing mice. Further, blocking TGF-beta or depleting Gr-1+ cells in vivo prevented the tumor recurrence, implying that TGF-beta made by a CD11b+ Gr-1+ myeloid cell, in an IL-13 and CD1d-restricted T cell-dependent mechanism, is necessary for down-regulation of tumor immunosurveillance. Identification of this stepwise regulation of immunosurveillance, involving CD1-restricted T cells, IL-13, myeloid cells, and TGF-beta, explains previous observations on myeloid suppressor cells or TGF-beta and provides insights for targeted approaches for cancer immunotherapy, including synergistic blockade of TGF-beta and IL-13.

Transforming growth factor-beta: innately bipolar.

Widely heralded for depressing ongoing immune responses, renewed interest in the proficiency by which transforming growth factor beta (TGF-beta) not only engages but also might drive an over-reactive innate response highlights its bipolar nature. Although coordination of the development and function of Treg, in addition to direct inhibition of cellular activation, are prominent pathways by which TGF-beta controls adaptive immunity, paradoxically TGF-beta appears instrumental in initiation of host responses to invasion through recruitment and activation of immune cells and persuasion of Th17 lineage commitment. Nevertheless, true to its manic-depressive behavior, new evidence links TGF-beta with depression of innate cells, including NK cells, and by way of a potential bridge between mast cells and Treg. Disruption of the tenuous balance between these opposing actions of TGF-beta underlies immunopathogenicity.