Heavy-chain antibody targeting of CD38 NAD+ hydrolase ectoenzyme to prevent fibrosis in multiple organs

The functionally pleiotropic ectoenzyme CD38 is a glycohydrolase widely expressed on immune and non-hematopoietic cells. By converting NAD+ to ADP-ribose and nicotinamide, CD38 governs organismal NAD+ homeostasis and the activity of NAD+-dependent cellular enzymes. CD38 has emerged as a major driver of age-related NAD+ decline underlying adverse metabolic states, frailty and reduced health span. CD38 is upregulated in systemic sclerosis (SSc), a chronic disease characterized by fibrosis in multiple organs. We sought to test the hypothesis that inhibition of the CD38 ecto-enzymatic activity using a heavy-chain monoclonal antibody Ab68 will, via augmenting organismal NAD+, prevent fibrosis in a mouse model of SSc characterized by NAD+ depletion. Here we show that treatment of mice with a non-cytotoxic heavy-chain antibody that selectively inhibits CD38 ectoenzyme resulted in NAD+ boosting that was associated with significant protection from fibrosis in multiple organs. These findings suggest that targeted inhibition of CD38 ecto-enzymatic activity could be a potential pharmacological approach for SSc fibrosis treatment.

Cutting Edge: The Expression of Transcription Inhibitor GFI1 Is Induced by Retinoic Acid to Rein in Th9 Polarization

IL-9, produced mainly by specialized T cells, mast cells, and group 2 innate lymphoid cells, regulates immune responses, including anti-helminth and allergic responses. Polarization of naive CD4 T cells into IL-9-producing T cells (Th9s) is induced by IL-4 and TGF-β1 or IL-1β. In this article, we report that the transcription factor growth factor-independent 1 transcriptional repressor (GFI1) plays a negative role in mouse Th9 polarization. Moreover, the expression of GFI1 is controlled by liganded RARα, allowing GFI1 to mediate the negative effect of retinoic acid on IL-9 expression. The Gfi1 gene has multiple RARα binding sites in the promoter region for recruiting nuclear coactivator steroid receptor coactivator-3 and p300 for histone epigenetic modifications in a retinoic acid-dependent manner. Retinoic acid-induced GFI1 binds the Il9 gene and suppresses its expression. Thus, GFI1 is a novel negative regulator of Il9 gene expression. The negative GFI1 pathway for IL-9 regulation provides a potential control point for Th9 activity.

Microbiome, Metabolism, and Immunoregulation of Asthma: An American Thoracic Society and National Institute of Allergy and Infectious Diseases Workshop Report

This report presents the proceedings from a workshop titled "Microbiome, Metabolism and Immunoregulation of Asthma" that was held virtually May 13 and 14, 2021. The workshop was jointly sponsored by the American Thoracic Society (Assembly on Allergy, Immunology, and Inflammation) and the National Institute of Allergy and Infectious Diseases. It convened an interdisciplinary group of experts with backgrounds in asthma immunology, microbiome science, metabolomics, computational biology, and translational pulmonary research. The main purpose was to identify key scientific gaps and needs to further advance research on microbial and metabolic mechanisms that may contribute to variable immune responses and disease heterogeneity in asthma. Discussions were structured around several topics, including 1) immune and microbial mechanisms of asthma pathogenesis in murine models, 2) the role of microbes in pediatric asthma exacerbations, 3) dysregulated metabolic pathways in asthma associated with obesity, 4) metabolism effects on macrophage function in adipose tissue and the lungs, 5) computational approaches to dissect microbiome-metabolite links, and 6) potential confounders of microbiome-disease associations in human studies. This report summarizes the major points of discussion, which included identification of specific knowledge gaps, challenges, and suggested directions for future research. These include questions surrounding mechanisms by which microbiota and metabolites shape host health versus an allergic or asthmatic state; direct and indirect influences of other biological factors, exposures, and comorbidities on these interactions; and ongoing technical and analytical gaps for clinical translation.

Differences in H3K4me3 and chromatin accessibility contribute to altered T-cell receptor signaling in neonatal naïve CD4 T cells

Neonatal CD4+ T cells have reduced or delayed T-cell receptor (TCR) signaling responses compared with adult cells, but the mechanisms underlying this are poorly understood. This study tested the hypothesis that human neonatal naïve CD4+ TCR signaling and activation deficits are related to differences in H3K4me3 patterning and chromatin accessibility. Following initiation of TCR signaling using anti-CD3/anti-CD28 beads, adult naïve CD4+ T cells demonstrated increased CD69, phospho-CD3ε and interleukin (IL)-2, tumor necrosis factor-α (TNF-α), interferon-γ and IL-17A compared with neonatal cells. By contrast, following TCR-independent activation using phorbol myristate acetate (PMA)/ionomycin, neonatal cells demonstrated increased expression of CD69, IL-2 and TNF-α and equivalent phospho-ERK compared with adult cells. H3K4me3 chromatin immunoprecipitation-sequencing (ChIP-seq) and assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) were performed on separate cohorts of naïve CD4+ T cells from term neonates and adults, and RNA-seq data from neonatal and adult naïve CD4+ T cells were obtained from the Blueprint Consortium. Adult cells demonstrated overall increased chromatin accessibility and a higher proportion of H3K4me3 sites associated with open chromatin and active gene transcription compared with neonatal cells. Adult cells demonstrated increased mRNA expression of the TCR-associated genes FYN, ITK, CD4, LCK and LAT, which was associated with increased H3K4me3 at the FYN and ITK gene loci and increased chromatin accessibility at the CD4, LCK and LAT loci. These findings indicate that neonatal TCR-dependent defects in activation are epigenetically regulated and provide a potentially targetable mechanism to enhance neonatal CD4+ T-cell responses.

Chorioamnionitis exposure remodels the unique histone modification landscape of neonatal monocytes and alters the expression of immune pathway genes

Chorioamnionitis is an intrauterine infection involving inflammation of the chorion, amnion, and placenta. It leads to a fetal systemic inflammatory response that can alter the transcription of neonatal immune genes. We have previously shown that neonatal monocytes gain the activating histone tail modification H3K4me3 at promoter sites of immunologically important genes as development progresses from preterm neonate to adult. In this study, we applied ChIP-seq and RNA-seq to evaluate the impact of chorioamnionitis on the neonatal monocyte H3K4me3 histone modification landscape over the course of fetal and neonatal immune system development. Chorioamnionitis exposure in neonatal monocytes resulted in a net increase in total monocyte H3K4me3, primarily in introns and intergenic regions. Immune gene expression was decreased in chorioamnionitis-exposed monocytes, with the majority of enriched transcripts falling into pathways that are not linked to the immune system. Over half of all neonatal monocyte H3K4me3 peaks, independent of their location, were associated with active gene transcription. Overall, chorioamnionitis exposure resulted in the global remodeling of the neonatal monocyte H3K4me3 landscape and changes in the expression of known immune genes. These changes resulted in a less robust inflammatory response upon exposure to a secondary challenge, which may explain why chorioamnionitis-exposed neonates have an increased risk of sepsis. DATABASE: ChIP-seq data for U30/O30/Term: GEO GSE81957 ChIP-seq data for U30C/O30C/TermC: GEO GSE111873 RNA-seq data for U/L/CU/CL: GEO GSE111927.

A role for Hox5 genes in T cell function during chronic allergic inflammation (HYP7P.268)

Allergic asthma is a significant health burden in western countries, and continues to increase in prevalence. T helper 2 (Th2) cells contribute to the development of disease through release of the cytokines interleukin (IL)-4, IL-5 and IL-13, resulting in increased airway eosinophils and mucus hypersecretion. While many factors are involved in the development of allergic asthma, the molecular mechanisms behind the disease remain largely unknown. As the three members of the Hox5 gene family (Hoxa5, Hoxb5 and Hoxc5) have been shown to play a role in lung development, we asked whether these genes also play a role in the adult lung in response to disease. We found that Hox5-deficient mice show exacerbated pathology compared to wild-type controls in a chronic allergen model, with an increased Th2 response as well as changes in lung tissue pathology. Examination of T cells from naïve wild-type or Hox5-deficient mice in Th2 polarizing conditions showed increased proliferation, enhanced Gata3 expression and production of IL-4, IL-5 and IL-13 in Hox5-deficient mice compared to wild-type controls. Overexpression of FLAG-tagged HOX5 proteins in Jurkat cells demonstrated HOX5 binding to the Gata3 locus, supporting a role for HOX5 proteins in direct transcriptional control of Th2 development. These results reveal a novel role for Hox5 genes as developmental regulators of immune cell function and Th2-induced pathology during allergic disease in the lung.

Lactobacilus johnsonii supplemented mice modulate RSV-induced disease and is associated with increased DHA metabolite that alters DC activation through PPAR- γ. (VIR9P.1148)

The gut microbiome contributes to a variety of mammalian processes, including modulation of host immune responses. We have found that L. johnsonii-supplemented mice displayed altered gut microbiome profiles and reduced RSV-induced pulmonary immunopathology. Metabolomics analysis of plasma from L. johnsonii-supplemented mice identified docosahexaenoic acid (DHA) and 2-hydroxyisobutyrate (butyrate precursor) as increased metabolites. We hypothesized that DHA and butyrate played a role in the modulation of the immune response in lung. We found that bone marrow-derived dendritic cells (BMDC) treated with DHA or butyrate expressed and produced reduced levels of IL-12, IL-6, IL-1β, IFN-β and TNF-α when stimulated with LPS, CpG or RSV compared to untreated cells. DHA treatment of RSV-infected BMDC prior to their co-culture with T cells isolated from RSV-infected mice significantly reduced their production of Th2 cytokines and IFNΥ. Then, we determined whether DHA was activating the nuclear receptor peroxisome proliferator-activated receptor gamma (PPAR-γ) in BMDC, which has been described as an inflammatory response inhibitor. We observed that BMDC treated with DHA and PPAR- γ antagonist (GW9662), had altered expression of mRNA and production of cytokines compared to DHA treated cells. These results suggest that DHA is modulating the immune response through PPAR-γ in dendritic cells and may be one mechanism of attenuating RSV immunopathology in mice supplemented with L. johnsonii.

An epigenetic mechanism of Dll4-facilitated Foxp3+ regulatory T cells differentiation (LYM8P.637)

Notch signaling facilitates inducible Foxp3+ regulatory T cells (iTreg) differentiation. Epigenetic modifications, which include histone modifications, are critical in cell differentiation. Recent genome-wide studies showed that iTreg have increased trimethylation on histone H3 at lysine 4 (H3K4me3) around Foxp3 loci, but the role of Notch signaling and its underlying epigenetic mechanisms remain elusive. Here we report that Delta-like ligand 4 (Dll4) but not Jagged1 can activate Notch signaling, facilitate Foxp3+ iTreg differentiation, and increased H3K4me3 around Foxp3 promoter and conserved noncoding sequences (CNS). We performed epigenetic enzyme array analysis and found one histone methyltransferase—SET and MYND domain containing protein 3 (Smyd3) that is abundant in iTreg. Dll4/Notch signaling amplified and accelerated Smyd3 expression in vitro during iTreg cell differentiation via an RBPJ-mediated transcription activation. Inhibition of Notch signaling decreased Smyd3 expression. When Smyd3 was genetically knocked out in CD4 T cells, the Dll4-enhanced H3K4me3 around the Foxp3 loci and Foxp3+ Tregs were decreased in vitro and in vivo. These results demonstrate that Notch ligand Dll4 can epigenetically regulate Foxp3+ Tregs through Smyd3.

Repression of the H3K4 demethylase Jarid1b leads to activation of RSV-infected dendritic cells (68.18)

Respiratory syncytial virus (RSV) is a common pathogen in children, with nearly all children being infected before the age of 2. Severe infection requiring hospitalization has been linked to the development of asthma later in life due to an improper Th2 skewing of the immune response. Dendritic cells (DCs) are key cells involved in presenting antigen to T cells and polarizing the T cell response. It has been reported that RSV interferes with the initiation of the adaptive immune response by inhibiting the production of type I interferons (IFN), including IFNβ, thus leading to a Th2 environment in the lungs. The mechanism by which this occurs is not fully understood. Epigenetic modulation of gene transcription has been shown to be important in regulating inflammatory pathways. We found that bone marrow derived DCs (BMDCs) infected with the RSV clinical isolate A2001/2-20 upregulated expression of Jarid1b, an H3K4 demethylase. Jarid1b has been described as a transcriptional repressor in cancer cells. We therefore hypothesized that Jarid1b plays a role in suppressing inflammatory genes in RSV infected DCs. We used siRNA to downregulate Jarid1b in BMDCs. Loss of Jarid1b led to a 10-fold increase in IFNβ compared to cells transfected with non-specific siRNA, as well as an increase in IL-6 and TNF-α. DC phenotype was unaffected as determined by flow cytometry. Investigations into the role that Jarid1b-induced DC regulation has in directing the T cell response are ongoing.

Lunatic Fringe: A key regulator of notch ligand Dll4 mediated Th2 inflammation during viral exacerbation of allergic response. (175.4)

Children exposed to environmental cockroach allergen (CRA) have increased susceptibility to develop chronic pulmonary disorders such as asthma later in their life. Moreover when these children encounter a respiratory viral infection it exacerbates their existing condition. The clinical manifestations include increased mucus production and airway hyperreactivity and peribronchial Th2 inflammation, necessitating immediate hospitalization and frequent recurrent hospital visits. In the present study we examined respiratory syncytial virus (RSV) exacerbated allergic responses. Previous studies showed that notch is required for the development of Th2 responses. However the role of notch ligand-Delta like-4 (Dll4) in viral exacerbation is unknown. Here, using a clinically relevant mouse model of RSV exacerbation an abrogation of mucus production and Th2 responses when Dll4 is blocked was observed. Further, our results from CD4-T cell skewing assays suggest that Dll4 augments IL4 production in Th2 cells in an antigen specific manner. Interestingly, both in vitro and in vivo an existing Th2 environment increased lunatic fringe (L-FNG) expression, a glycosyltransferase that enhances Notch activation by ligands of the Delta-like family, in CD4 T cells. Using loss of function assays and an RNAi approach we show that Dll4 augmented IL4 production is L-FNG dependent. These studies highlight a novel regulatory mechanism involved in Dll4 mediated Th2 responses during viral exacerbation.

Autophagy in dendritic cells modulates CD4+ T cell response during RSV infection (106.9)

Severe respiratory syncytial virus (RSV) infections cause significant morbidity among susceptible individuals, especially infants. During viral infection, dendritic cells (DC) prime appropriate adaptive immune responses through antigen presentation, cytokine production and costimulation of T cells. Previous studies suggest that macroautophagy, an intracellular process delivering cytoplasmic constituents to endosomes for degradation, functions in intracellular pathogen surveillance and antigen delivery for presentation by DC. RSV infection of bone marrow-derived dendritic cells (BMDC) stimulates autophagosome formation, while siRNA knockdown of LC3 prior to RSV infection reduces innate cytokine production. Pulmonary DCs from RSV-infected LC3b-deficient mice show dysregulated maturation through altered MHC class II and costimulatory molecule expression. BMDC cultured from LC3b-deficient mice skew primary and secondary T cell responses toward Th17, while decreasing expression of IFNγ and Th2 cytokines. These results suggest that virally-induced autophagy in DC modulates the host response to RSV infection through altered activation of CD4+ T cells.

The role of SIRT1 in the activation of innate immune responses during RSV infection (68.6)

Respiratory syncytial virus (RSV) infection is the leading cause of lower respiratory tract infection in infants and children worldwide. Dendritic cells (DC) prime the adaptive immune response by recognizing and delivering viral antigens to local lymph nodes, presenting antigen to T cells, displaying co-stimulatory markers, and releasing cytokines. Recent studies have linked macroautophagy to intracellular pathogen recognition and the activation of DCs leading to enhanced antigen-presenting cell (APC) function. SIRT1, a NAD+ dependent deacetylase, acts on many cellular substrates, including autophagy proteins (Atg), as shown with Sirt1-/- mice that accumulate damaged organelles similar to Atg5-/- mice. Our study investigates the role of SIRT1 in DC maturation, subsequent T cell activation, and RSV-induced pulmonary pathology. RSV infected bone marrow-derived DCs (BMDC) pre-treated with EX-527, a SIRT1 inhibitor, downregulate expression of key cytokines, MHCII, and CD86. EX527 treatment of RSV- infected wild-type mice resulted in increases in lung mucus production, viral load, and TH2 cytokine production. Likewise, EX527 significantly antagonizes TLR7-induced cytokine release in RSV-infected BMDCs, suggesting a link with the TLR/PAMP recognition response. These results suggest that SIRT1 may be a critical determinant in the innate immune response and resultant pulmonary pathology during RSV infection.

TSLP promotes induction of Th2 differentiation but is not necessary during established allergen-induced pulmonary disease (57.13)

Thymic stromal lymphopoietin (TSLP) has been implicated in allergic inflammation by promoting a Th2-type response. Using in vitro cultures we demonstrated that TSLP played a critical role in the development of Th2 immune responses, but its role on an established Th2 immune environment was not significant. Adoptive transfer of naive DO11.10 ovalbumin (OVA)-specific T cells followed by exposure of OVA showed an early impairment of Th2 immune response in TSLP-/- mice compared to wild type (WT) mice. In contrast, transfer of differentiated Th2 cells into TSLP-/- mice did not change lung pathology or Th2 cytokine production compared to transfer into WT mice. Using a well-established allergen-induced Th2 model demonstrated that there was no difference between WT and TSLP-/- mice. Furthermore, when we treated allergic animals with established disease with a neutralizing anti-TSLP antibody there was no change in airway hyerreponsiveness (AHR) or Th2 cytokine production compared to the control antibody treated animals. Collectively, these studies suggest that in mice TSLP has an important role during the early development of Th2 immune responses. However, TSLP appears to have a minimal role at later stages of allergic disease suggesting that it may not be required for maintaining a persistent and established Th2 immune environment. These studies may offer important data for determining whether targeting TSLP would be beneficial for therapy in established Th2 mediated diseases.

Gas6/TAM signaling differentially modulates chronic fungal asthma with the expansion of myeloid regulatory cell subsets in mice (57.7)

Gas6, a Tyro3, Axl, Mertk (TAM) receptor ligand, is detected in a variety of diseases and has various roles. Herein, we show that Gas6 differentially modulates experimental fungal asthmatic response via the expansion and modulation of myeloid-derived regulatory cells (MDRCs). Aspergillus fumigatus-sensitized mice were challenged with live Aspergillus conidia and received approximately 2 μg (low) or 7 μg (high) of recombinant Gas6 via intranasal installation from days 14 to 28 after conidia challenge. In the low dose Gas6 group, significant airway hyperresponsiveness (AHR), airway remodeling, and whole lung IL-13 were observed compared with the control group. Although high dose Gas6 treatment significantly suppressed AHR and the whole lung levels of inflammatory cytokines compared with control, this treatment exacerbated airway remodeling. MDRCs have both disease enhancing and suppressing cells in asthma. Indeed, low dose Gas6 treatment increased the accumulation of CD11b+F4/80+Ly6C-Ly6G+ MDRC with pro-inflammatory properties into asthmatic lung whereas high dose Gas6 promoted the accumulation of immunosuppressive CD11b+F4/80+Ly6C+Ly6G- MDRC during chronic asthma. Anti-Axl Ab, but not anti-Mer Ab, treatment significantly suppressed not only AHR but also airway remodeling in asthmatic mice compared with IgG control asthmatic groups. Together, these results demonstrate that Gas6-TAM receptor interactions modulate fungal asthma, in part through effects on MDRCs.

Crucial role for IPS-1 signaling in mediating anti-viral responses and clearance of Respiratory Syncytial Virus (170.4)

Upon replication of Respiratory Syncytial Virus (RSV), double-stranded viral RNA can be detected in the endosomes via Toll-like receptor 3 (TLR3) signaling or by the cytoplasmic helicases retinoic acid inducible gene I (RIG-I) and melanoma differentiation-associated gene (Mda5). The latter interact downstream with IFNβ promoter stimulator (IPS-1). We previously demonstrated that TLR3 deficiency worsens RSV-induced lung pathology, yet leaves viral clearance intact. The present study examined the importance of IPS-1 signaling for anti-viral responses in primary cultures of alveolar epithelial cells (AECs), in dendritic cells (DCs), and macrophages (mΦ), as well as in vivo using IPS-1 knockout (KO) mice. In AECs, RSV induced IFNβ, IL6, CXCL1, CCL2 and CCL5 in an IPS-1 dependent manner. In DCs, the expression of IFNβ and CCL2 also required IPS-1. Conversely, RSV-induced cytokine and chemokine expression was enhanced in IPS-1 KO mΦ, while T-cells of infected IPS-1 KO mice showed a predominant Th1 profile with increased IFNγ. Plaque assays revealed higher RSV titers in IPS-1 deficient mice, accompanied by more severe granulocytic infiltration. Our data suggest a significant contribution of the IPS-1 pathway to the RSV-induced type I interferon response and inflammatory cytokine/chemokine production. Future experiments, using bone marrow chimeras, will help to elucidate the role of IPS-1 in both the structural and hematopoietic mediated response to viral infection.

Fibrocytes contribute to the increased levels of fibrosis observed in Th2 pulmonary granulomas in TLR9-/- mice (54.18)

Despite many recent advances in the field, the underlying mechanisms governing pulmonary fibrosis remain poorly understood. We have used an experimental system of fibrotic granuloma development via the embolization of Schistosoma mansoni eggs to the lungs. Egg embolization results in the release of highly antigenic glycoproteins (Schistosoma egg antigen,SEA) that promote a dominant Th2 immune response. We previously demonstrated that in comparison to wild-type mice, TLR9-/- mice showed increased granuloma size and augmented collagen deposition. In the present study, we investigated the mechanisms underlying the fibrotic change of this Th2-driven pulmonary granuloma system, and the contribution of TLR9 signals to this phenomenon. The chemokine receptor/ligand pair CXCR4/CXCL12 has been shown to play an important role in the homing of fibrocytes; these cells express CXCR4 and migrate in response to CXCL12 in a model of bleomycin-induced pulmonary fibrosis. Levels of CXCL12 were higher in the lungs of mice treated with S. mansoni eggs, but there were no difference between wild-type and TLR9-/- mice. Flow cytometry data indicated that TLR9-/- mice showed increased number of CD45+Col I+CXCR4+ fibrocytes in the lungs of TLR9-/- mice treated with S. mansoni eggs in comparison to wild-type mice. Thus, our results suggested that increased fibrocytes may contribute to the increased levels of fibrosis observed in TLR9-/- mice.

Increased IL-17 production in post-septic mice exacerbates respiratory syncytial virus induced immunopathology of the lung (49.25)

Survivors of severe sepsis exhibit increased morbidity and mortality in response to secondary infections. Although bacterial secondary infections have been widely studied, there remains a paucity of data with viral infections post sepsis. Here, we show in an experimental mouse model of severe sepsis (cecal ligation and puncture, CLP) followed by respiratory syncytial virus (RSV) infection, exacerbated immunopathology in the lungs of CLP mice compared to RSV infected sham surgery mice. The immunopathology associated with the viral infection in CLP mice was in part due to increased mucus production in the lungs and impaired ability of septic mice to clear the virus. These findings correlated with increased IL-17 production in the lungs of RSV-infected CLP mice. RSV-infected CLP mice had increased levels of Th2 cytokines and reduced IFNγ in the lungs and lymph nodes compared to RSV infected sham mice. In addition, CD4 T cells from CLP mice ex vivo increased IL-17 production irrespective of the skewing conditions. Further, in vivo neutralization of IL-17 prior to RSV infection led to a significant reduction in virus induced mucus production and Th2 cytokines. Taken together, these data provide evidence that post septic CD4+T cells are primed toward IL-17 production, which may contribute to the immunopathology of a secondary viral infection.

MHV68 latency modulates host immune responses to H1N1 influenza virus (49.9)

Human gammaherpesviruses such as Epstein-Barr virus (EBV) are clinically important pathogens, as diseases caused by gammaherpesvirus infection are a significant human health concern. Additionally, latent gammaherpesvirus infection is widespread, and can have a profound effect on subsequent immune responses. Murine gammaherpesvirus 68 (MHV68) is a natural rodent pathogen that has been used as a model to study the pathogenesis of human gammaherpesviruses. Like other herpesviruses, MHV68 causes acute infection and establishes life-long latency in the host. Recently, it has been shown that mice latently infected with MHV68 have resistance to unrelated pathogens in secondary infection models. We therefore hypothesized that latent MHV68 infection can modulate host response to H1N1 influenza virus, a serotype with high associated mortality rates in humans. To test this hypothesis, mice were infected intranasally with influenza virus following the establishment of MHV68 latency. Mice latently infected with MHV68 showed significantly higher survival of H1N1 influenza virus infection than mock-infected mice. Latent MHV68 infection led to lower influenza viral loads in the lungs, as well as decreased inflammatory pathology in the lungs. Collectively, our findings indicate that latent MHV68 infection has a protective effect against H1N1 influenza virus infection.

Differential regulation of post-transplant viral host defense by donor versus host regulatory T cells (154.40)

Respiratory syncytial virus (RSV) infection is a significant cause of morbidity and mortality following hematopoietic cell transplant (HCT). We used a murine model of autologous HCT to investigate the roles played by regulatory T cells (Treg) in host defense against RSV infection post-transplant. Regulatory T cells were highly enriched in the CD4+ T cell compartment up to five weeks post-transplant (>30% of lung CD4+ T cells at week 2 post-transplant, versus 5-10% in controls). The increased frequency of Tregs resulted from 1) survival recipient-derived cells, 2) increased proliferation of Tregs compared to Teff, and 3) differentiation of induced Treg (iTreg). Using Foxp3-DTR mice, DT- mediated ablation of recipient-derived Tregs led to increased lung leukocytes (CD45+, CD4+, CD8+, and CD11b+CD11c+ cells). Total numbers of IFNγ+ CD4+, IL-17+CD4+, IFNγ+CD8+ T cells were all increased in recipient Treg ablated mice. Remarkably, ablation of donor Tregs led to decreases in the same pulmonary leukocyte subsets, and decreased effector T cell (CD4+IFNγ+ and CD8+IFNγ+) responses. Ablation of donor (but not recipient) Tregs impaired viral clearance. In other studies, mature Foxp3+ CD4+ T cells co-transferred at transplant lost Foxp3 expression (>30% by week 4), suggesting instability of Tregs in the post-transplant environment. Together, these studies indicate differential (and possibly, competing) functions for Tregs in post-transplant host defense.

Notch ligand Delta-like 4 regulates development and pathogenesis of allergic airway responses by modulating IL-2 production and Th2 immunity (141.15)

Activation of the conical Notch pathways have been implicated in Th cell differentiation, but the role of specific Notch ligands in Th2 mediated allergic airway responses has not been completely elucidated. In this study, we show that delta-like 4 (Dll4) was up-regulated on dendritic cells in response to cockroach allergen. Blocking Dll4 in vivo at either the afferent or efferent phases of the immune response enhanced allergen-induced pathogenic responses including airway hyperresponsiveness (AHR) and mucus production via increased Th2 cytokines. In vitro assays demonstrated that Dll4 regulates IL-2 in T cells from established Th2 responses as well as during primary stimulation. Interestingly, Dll4 blockade during the afferent, but not the efferent phase, increased IL-2 levels in lung and lymph node of allergic mice. Moreover, Dll4-mediated Notch activation of T cells during primary stimulation in vitro increased apoptosis during the contraction/resting phase of the response, which could be rescued by exogenous IL-2. Consistent with the role for Dll4-mediated IL-2 regulation in overall T cell function, the frequency of IL-4 producing cells were also significantly altered by Dll4 both in vivo and in vitro. These data demonstrate a regulatory role of Dll4 on both Th2 differentiation as well as on Th2 cytokine production in established Th2 responses.

Delta-like ligand 4 regulation of effector T cell function during experimental autoimmune encephalomyelitis (96.8)

Notch signaling mediates cell fate decisions through specific ligand-receptor binding. Signaling by Delta-like ligand 4 (DLL4) influences both CD4+ Th1 and Th17-associated cytokine production and contributes to adaptive immunity. Experimental autoimmune encephalomyelitis (EAE) is an autoimmune disease of the central nervous system (CNS) that is mediated by autoreactive Th1 and Th17 CD4+ T cells. We examined the contributions of DLL4 in regulating Th1 and Th17 functions during EAE. CNS-infiltrating myeloid dendritic cells, macrophage and resident microglia express high levels of DLL4 during EAE. Blocking DLL4 during antigen-restimulation of primed T cells resulted in decreased inflammatory cytokine production by these T cells. Administration of anti-DLL4 to PLP139-151-primed mice decreased EAE severity. Similarly, pretreatment of PLP139-151-specific T cells with anti-DLL4 reduced adoptive disease transfer. Treatment of mice with anti-DLL4 following adoptive transfer of primed T lymphocytes blocks localization of these T cells to the CNS and prevents disease. These results suggest DLL4-Notch signaling regulates autoimmune T cell effector function and localization to the CNS. (Supported by NMSS RG4146-A-4)

The chemokine MIP1alpha/CCL3 determines pathology in primary RSV infection by regulating the balance of T cell populations in the murine lung

Background

CD8 T cells assist in the clearance of respiratory syncytial virus (RSV) infection from the lungs. However, disease after RSV infection is in part caused by excessive T cell activity, and a balance is therefore needed between beneficial and harmful cellular immune responses. The chemokine CCL3 (MIP1α) is produced following RSV infection and is broadly chemotactic for both T cells and natural killer (NK) cells. We therefore investigated its role in RSV disease.

Methodology/Principal Findings

CCL3 was produced biphasically, in both the early (day 1) and late (day 6–7) stages of infection. CCL3 depletion did not alter the recruitment of natural killer (NK) cells to the lungs during the early stage, but depletion did affect the later adaptive phase. While fewer T cells were recruited to the lungs of either CCL3 knockout or anti-CCL3 treated RSV infected mice, more RSV-specific pro-inflammatory T cells were recruited to the lung when CCL3 responses were impaired. This increase in RSV-specific pro-inflammatory T cells was accompanied by increased weight loss and illness after RSV infection.

Conclusions/Significance

CCL3 regulates the balance of T cell populations in the lung and can alter the outcome of RSV infection. Understanding the role of inflammatory mediators in the recruitment of pathogenic T cells to the lungs may lead to novel methods to control RSV disease.

Altered T lymphocyte response to respiratory syncytial virus in CCR6−/− mice (96.3)

The CC chemokine receptor 6 is unique in the chemokine family because it binds to only a single ligand, CCL20. CCL20 is expressed in epithelial cells in tissues such as skin, gut mucosa and lungs. Studies using CCR6 deficient mice revealed a defect in dendritic cell positioning in the gut mucosa, suggesting a role for CCL20-CCR6 in leukocyte homeostasis and proper positioning of these cells in mucosal tissues. In a mouse model of asthma, CCR6−/− mice showed reduced airway hyperreactivity and less mucus production. The potential pathological role for CCL20-CCR6 led us to investigate this receptor-ligand pair in a mouse model of viral infection caused by respiratory syncytial virus (RSV), a negative strand RNA virus that can cause severe complications in infants, the elderly and immunocompromised individuals. We found that CCR6−/− mice had lower numbers of activated CD4 and CD8 T cells in the lungs at days 6 and 9 post-RSV infection, as well as reduced Th1 and Th2 cytokines in both lungs and lymph nodes. Interestingly, we also found that these mice had more efficiently cleared virus by day 6 post-infection. This suggests the involvement of a cell type other than T lymphocytes that in the absence of CCR6 is able to impart viral immunity.

This research is supported by NIH grant AI36302

Respiratory viral infections drive chemokine expression and exacerbate the asthmatic response

A number of investigations have linked respiratory vial infections and the intensity and subsequent exacerbation of asthma through host response mechanisms. For example, it is likely that the immune-inflammatory response to respiratory syncytial virus can cause a predisposition toward an intense inflammatory reaction associated with asthma, and adenovirus might cause exacerbation of the immune response associated with chronic obstructive pulmonary disease. In each of these situations, the host's immune response plays a critical mechanistic role through the production of certain cytokines and chemokines. Specific aspects of these augmented immune responses are determined by the biology of the virus, the genetic variability of the host, and the cytokine-chemokine phenotype of the involved tissue. For instance, the type 1/type 2 cytokine ratio in the airways during infection with rhinovirus determines how long the viral infection endures. By this same theory, it has been demonstrated that chemokine levels produced during respiratory syncytial virus infection determine host responses to later immune stimuli in the lung, with the potential to augment the asthmatic response. Further research in this area will clarify cytokines, chemokines, or cell targets, which will provide the basis for next-generation therapies.

Therapeutic effect of IL-13 immunoneutralization during chronic experimental fungal asthma

IL-13 and IL-4 are key contributors to the asthmatic phenotype. The temporal role of these cytokines in airway function, inflammation, and remodeling were assessed in a chronic murine model of Asperigillus fumigatus-induced allergic asthma. IL-13 and IL-4 protein levels were significantly elevated by 30 days after conidia challenge in A. fumigatus-sensitized mice. Furthermore, IL-13Ralpha1 mRNA expression was significantly elevated 7 days after conidia challenge and remained elevated until day 21. In contrast, IL-13Ralpha2 mRNA expression, although constitutively expressed in naive lung, was absent in the lungs of A. fumigatus-sensitized mice both before and after conidia challenge. Membrane-bound IL-4R mRNA expression was significantly elevated 7 days after conidia challenge; however, soluble IL-4R mRNA expression was increased 30 days after conidia challenge. Immunoneutralization of IL-13 between days 14 and 30 or days 30 and 38 after fungal sensitization and challenge significantly attenuated airway hyperresponsiveness, collagen deposition, and goblet cell hyperplasia at day 38 after conidia challenge; however, the effects of IL-4 immunoneutralization during the same time periods were not as marked. IFN-gamma and IL-12 release after Aspergillus Ag restimulation was elevated from spleen cells isolated from mice treated with IL-4 anti-serum compared with IL-13 anti-serum or normal rabbit serum-treated mice. This study demonstrates a pronounced therapeutic effect of IL-13-immunoneutralization at extended time points following the induction of chronic asthma. Most importantly, these therapeutic effects were not reversed following cessation of treatment, and IL-13 anti-serum treatment did not alter the systemic immune response to Ag restimulation, unlike IL-4 immunoneutralization. Therefore, IL-13 provides an attractive therapeutic target in allergic asthma.

Determination of preferential binding sites for anti-dsRNA antibodies on double-stranded RNA by scanning force microscopy

The monoclonal anti-dsRNA antibody J2 binds double-stranded RNAs (dsRNA) in an apparently sequence-nonspecific way. The mAb only recognizes antigens with double-stranded regions of at least 40 bp and its affinity to poly(A) poly(U) and to dsRNAs with mixed base pair composition is about tenfold higher than to poly(I) poly(C). Because no specific binding site could be determined, the number, the exact dimensions, and other distinct features of the binding sites on a given antigen are difficult to evaluate by biochemical methods. We therefore employed scanning force microscopy (SFM) as a method to analyze antibody-dsRNA interaction and protein-RNA binding in general. Several in vitro-synthesized dsRNA substrates, generated from the Dictyostelium PSV-A gene, were used. In addition to the expected sequence-nonspecific binding, imaging of the complexes indicated preferential binding of antibodies to the ends of dsRNA molecules as well as to certain internal sites. Analysis of 2,000 bound antibodies suggested that the consensus sequence of a preferential internal binding site is A2N9A3N9A2, thus presenting A residues on one face of the helix. The site was verified by site-directed mutagenesis, which abolished preferential binding to this region. The data demonstrate that SFM can be efficiently used to identify and characterize binding sites for proteins with no or incomplete sequence specificity. This is especially the case for many proteins involved in RNA metabolism.

Local production of chemokines during experimental vaginal candidiasis

Recurrent vulvovaginal candidiasis, caused by Candida albicans, is a significant problem in women of childbearing age. Although cell-mediated immunity (CMI) due to T cells and cytokines is the predominant host defense mechanism against C. albicans at mucosal tissue sites, host defense mechanisms against C. albicans at the vaginal mucosa are poorly understood. Based on an estrogen-dependent murine model of vaginal candidiasis, our data suggest that systemic CMI is ineffective against C. albicans vaginal infections. Thus, we have postulated that local immune mechanisms are critical for protection against infection. In the present study, the kinetic production of chemokines normally associated with the chemotaxis of T cells, macrophages (RANTES, MIP-1alpha, MCP-1), and polymorphonuclear neutrophils (MIP-2) was examined following intravaginal inoculation of C. albicans in estrogen-treated or untreated mice. Results showed significant increases in MCP-1 protein and mRNA in vaginal tissue of infected mice as early as 2 and 4 days postinoculation, respectively, that continued through a 21-day observation period, irrespective of estrogen status. No significant changes were observed with RANTES, MIP-1alpha, or MIP-2, although relatively high constitutive levels of RANTES mRNA and MIP-2 protein were observed. Furthermore, intravaginal immunoneutralization of MCP-1 with anti-MCP-1 antibodies resulted in a significant increase in vaginal fungal burden early during infection, suggesting that MCP-1 plays some role in reducing the fungal burden during vaginal infection. However, the lack of changes in leukocyte profiles in vaginal lavage fluids collected from infected versus uninfected mice suggests that MCP-1 functions to control vaginal C. albicans titers in a manner independent of cellular chemotactic activity.

Interferon-induced protein 10 and interleukin 8. C-X-C chemokines present in proliferative diabetic retinopathy

OBJECTIVE

To determine vitreous levels of interleukin 8 (IL-8) and interferon-induced protein 10 (IP-10), which are members of the C-X-C chemokine family that promote and inhibit neovascularization, respectively.

METHODS

We measured the levels of IL-8 and IP-10 by specific enzyme-linked immunosorbent assays in the vitreous from 30 patients with proliferative diabetic retinopathy (PDR) and 10 control patients undergoing vitrectomy for idiopathic macular holes or idiopathic macular puckers.

RESULTS

Detectable levels of IL-8 were found in 23 of 24 patients with active PDR, 4 of 6 patients with inactive PDR, and 6 of 10 controls. Levels of IL-8 were significantly increased in vitreous samples from the patients with active PDR (P = .02) when compared with vitreous samples from the controls. The IL-8 levels detected in vitreous samples from patients with inactive PDR were not significantly elevated over those found in the control samples. Interferon-induced protein 10 was detected in the vitreous samples from 23 of 24 patients with active PDR, all patients with inactive PDR, and 9 of 10 controls. Significant elevations of IP-10 were measured in samples from patients with active PDR (P = .004) and in those with inactive PDR (P = .00) over those from controls. In addition, levels of IP-10 were significantly elevated in vitreous samples from patients with inactive PDR compared with vitreous samples from patients with active PDR (P = .02).

CONCLUSION

Both IL-8 and IP-10 participate in the pathogenesis of PDR.

The role of IL-5 in bleomycin-induced pulmonary fibrosis

Eosinophils are known to express cytokines capable of promoting fibrosis. Interleukin-5 (IL-5) is important in regulating eosinophilopoiesis, eosinophil recruitment and activation. Lung IL-5 expression is elevated in pulmonary fibrosis, wherein the eosinophil is a primary source of fibrogenic cytokines. To determine the role of IL-5 in pulmonary fibrosis, the effects of anti-IL-5 antibody were investigated in a model of bleomycin-induced pulmonary fibrosis. Fibrosis was induced in mice by endotracheal bleomycin treatment. Animals were also treated with either anti-IL-5 antibody or control IgG. Lungs were then analyzed for fibrosis, eosinophil influx, chemotactic activity, and cytokine expression. The results show that a primary chemotactic activity at the height of eosinophil recruitment is IL-5. Furthermore, anti-IL-5 antibody caused significant reduction in lung eosinophilia, cytokine expression, and fibrosis. These findings taken together suggest an important role for IL-5 in pulmonary fibrosis via its ability to regulate eosinophilic inflammation, and thus eosinophil-dependent fibrogenic cytokine production.

TNF and IL-6 mediate MIP-1alpha expression in bleomycin-induced lung injury

Previously, macrophage inflammatory protein-1alpha (MIP-1alpha), a member of the C-C chemokine family, has been implicated in bleomycin-induced pulmonary fibrosis, a model of the human disease idiopathic pulmonary fibrosis. Neutralization of MIP-1alpha protein with anti-MIP-1alpha antibodies significantly attenuated both mononuclear phagocyte recruitment and pulmonary fibrosis in bleomycin-challenged CBA/J mice. However, the specific stimuli for MIP-1alpha expression in the bleomycin-induced lesion have not been characterized. In this report, two mediators of the inflammatory response to bleomycin, tumor necrosis factor (TNF) and interleukin-6 (IL-6), were evaluated as putative stimuli for MIP-1alpha expression after bleomycin challenge in CBA/J mice. Elevated levels of bioactive TNF and IL-6 were detected in bronchoalveolar lavage (BAL) fluid and lung homogenates from bleomycin-treated CBA/J mice at time points post-bleomycin challenge, which precede MIP-1alpha protein expression. Treatment of bleomycin-challenged mice with soluble TNF receptor (sTNFr) or anti-IL-6 antibodies significantly decreased MIP-1alpha protein expression in the lungs. Furthermore, normal alveolar macrophages secreted elevated levels of MIP-1alpha protein in response to treatment with TNF plus IL-6 or bleomycin plus IL-6, but not TNF, bleomycin, or IL-6 alone. Finally, leukocytes recovered from the BAL fluid of bleomycin-challenged mice secreted higher levels of MIP-1alpha protein, compared to controls, when treated with TNF alone. Based on the data presented here, we propose that TNF and IL-6 are part of a cytokine network that modulates MIP-1alpha protein expression in the profibrotic inflammatory lesion during the response to intratracheal bleomycin challenge.

Tumor necrosis factor up-regulates intercellular adhesion molecule 1, which is important in the neutrophil-dependent lung and liver injury associated with hepatic ischemia and reperfusion in the rat

Tumor necrosis factor (TNF) is released during hepatic ischemia/reperfusion (I/R) and plays an important role in the ensuing neutrophil-mediated lung and liver injury. Since TNF is not a direct neutrophil chemotaxin, we hypothesized that TNF may up-regulate neutrophil adhesion molecules, specifically intercellular adhesion molecule-1 (ICAM-1), following hepatic I/R, and that this molecule then plays an important role in tissue neutrophil influx. Rats underwent 90 min of lobar hepatic ischemia with reperfusion. Pulmonary and hepatic ICAM-1 expression were assessed by reverse transcription-polymerase chain reaction, Western blot analysis, and immunohistochemical staining. Increases in hepatic ICAM-1 were demonstrated within 1 h of reperfusion, while increases in pulmonary ICAM-1 were not seen until 6 h of reperfusion. Next, rats were treated with anti-TNF antibody or control antibody without TNF neutralizing properties prior to hepatic I/R. Pretreatment with anti-TNF antibody significantly decreased pulmonary and hepatic ICAM-1 expression after hepatic I/R. We next investigated the effects of pretreatment with anti-ICAM-1 antibodies on the lung and liver injury that follows hepatic I/R. Lung injury was assessed by changes in pulmonary capillary permeability as estimated by extravasation of Evans Blue dye and pulmonary neutrophil influx as measured by lung myeloperoxidase levels. Liver injury was assessed by hepatic neutrophil morphometrics and plasma liver enzymes (alanine aminotransferase). Pretreatment with anti-ICAM-1 antibodies significantly decreased pulmonary capillary permeability, pulmonary myeloperoxidase, hepatic neutrophil influx, and plasma alanine aminotransferase, as compared to animals pretreated with control antibody. These data suggest that TNF is a proximal trigger for pulmonary and hepatic ICAM-1 up-regulation following hepatic ischemia with reperfusion, and that ICAM-1 is important for pulmonary and hepatic neutrophil influx, with the resultant tissue injury, following hepatic I/R.

Cytokine and chemokine production in HSV-1 latently infected trigeminal ganglion cell cultures: effects of hyperthermic stress

The establishment of a primary trigeminal ganglion (TG) cell culture latently infected with herpes simplex virus type 1 (HSV-1) has been useful in studying stress-induced reactivation of the latent virus. However, the immune profile of this culture system prior to and after stress has never been established. In the present manuscript, cytokine and chemokine production were measured in primary cultures of TG cells obtained from uninfected and HSV-1 latently infected mice. Supernates from TG cell cultures contained detectable interleukin (IL)-6 but not IL-1beta, IL-2, IL-10, interferon (IFN)-gamma or tumor necrosis factor (TNF)-alpha as determined by ELISA. The basal level of IL-6 in uninfected TG cell cultures was 20.5 +/- 2.3 ng/ml, whereas latently infected TG cells produced significantly less IL-6 (12.1 +/- 1.9 ng/ml). Supernates from TG cell cultures also contained detectable levels of C-10, MCP-1 and eotaxin but little to no MIP-1alpha, MIP-1beta, or MIP-2. While there were no differences in the basal level of MCP-1 and eotaxin in TG cell cultures from HSV-1-infected and uninfected mice, C10 levels were significantly higher in TG cultures originating from infected mice compared to uninfected ones (5.86 +/- 0.61 ng/ml compared to 1.18 +/- 0.16 ng/ml). Hyperthermic stress (43 degrees C, 180 min), which induces reactivation of latent HSV-1 from TG cell cultures, significantly reduced IL-6 and C-10 levels from both uninfected and latently infected TG cell cultures. However, there was no correlation between cytokine/chemokine levels and HSV-1 reactivation. Immunofluorescent studies showed TG cell cultures contained 10% MAC-3+ staining cells (macrophage specific) but no dendritic cells. By comparison, cells from freshly isolated TG contained 6% positive dendritic cells but < 1% MAC-3 + cells. Both in vivo and in vitro TG consisted of a low percentage of CD3+ and CD8+ cells. Hyperthermic stress (43 degrees C for 3 h) eliminated the lymphocyte population as determined by RT-PCR. Whereas no spontaneous reactivation has been reported in mice, spontaneous reactivation occurred in 4.5% (10/220) of TG cell cultures surveyed over a 20 day period. Collectively, the dichotomy between HSV-1 replication and reactivation comparing the in vitro and in vivo HSV-1 latency models may reside, in part, to the differences in the levels of cytokines, chemokines and immune cell populations within the microenvironment of the in vitro and in vivo TG.

Therapeutic effects of nitric oxide inhibition during experimental fecal peritonitis: role of interleukin-10 and monocyte chemoattractant protein 1

This study demonstrates that the therapeutic effect of a nitric oxide inhibitor in a murine model of fecal peritonitis is mediated in part by increased levels of interleukin-10 (IL-10) and monocyte chemoattractant protein 1 (MCP-1). Female CD1 mice were subjected to cecal ligation and puncture (CLP) with a 21-gauge needle and, immediately following surgery, were injected intraperitoneally with saline, N(G)-nitro-L-arginine methyl ester (L-NAME; 8 mg/kg), or N(G)-nitro-D-arginine methyl ester (D-NAME; 8 mg/kg). At 96 h after surgery and drug treatment, 20% of mice that received D-NAME had survived whereas 60% of mice that received L-NAME were alive. To elucidate the effect of L-NAME treatment on chemokine and cytokine production during fecal peritonitis, the levels of macrophage inflammatory protein 2 (MIP-2), IL-10, and MCP-1 were measured in peritoneal washings from additional groups of mice 24 h after the CLP surgery. Peritoneal fluids from L-NAME-treated mice contained significantly higher levels of IL-10 and MCP-1 than did those from D-NAME-treated mice. To elucidate the effect of nitric oxide inhibition on potential cellular sources of IL-10 and MCP-1 in the CLP model, cultured alveolar and peritoneal macrophages were activated with bacterial lipopolysaccharide in the presence of L-NAME; these macrophages produced significantly more MCP-1 than did similarly activated macrophages in the presence of D-NAME. In the CLP surgery model, immunoneutralization of IL-10 alone or IL-10 and MCP-1 together with polyclonal antibodies prior to surgery significantly reduced the survival rates in L-NAME-treated groups compared with L-NAME-treated groups that received preimmune serum. Taken together, these data demonstrate that the inhibition of nitric oxide following experimental CLP fecal peritonitis is therapeutic, in part through the modulatory effect of this treatment on the synthesis of IL-10 and MCP-1.

Mycobacterial and schistosomal antigen-elicited granuloma formation in IFN-gamma and IL-4 knockout mice: analysis of local and regional cytokine and chemokine networks

Type 1 (IFN-gamma/TNF-dominant) and 2 (IL-4/IL-5-dominant) granulomatous inflammation were analyzed in mice with knockout of IFN-gamma or IL-4 genes. Lung granulomas were elicited by beads coated with purified protein derivative (PPD) of Mycobacteria bovis or soluble Schistosoma mansoni egg Ags. Parameters included granuloma size, composition, and macrophage function; white blood cell differentials; lymph node cytokine profiles; and cytokine/chemokine mRNA expression by lungs. Type 1 (PPD) and 2 (soluble Schistosoma mansoni egg Ags) responses showed characteristic cytokine and chemokine profiles in control mice. IFN-gamma knockout converted the PPD response to a type 2-like pattern with eosinophil infiltration and decreased TNF and RANTES, but increased IL-4, IL-5, IL-10, IL-13, monocyte chemoattractant protein-3 (MCP-3), and eotaxin expression. IL-4 knockout exacerbated type 1 inflammation with increased IL-2/IFN-gamma production by lymph nodes and IL-1 production by granuloma macrophages, but unexpectedly, IFN-gamma transcripts were reduced in lungs. Regarding the type 2 response, IL-4 was needed for maximal blood eosinophilia, but surprisingly, its absence had a minimal effect on type 2 granuloma size and composition despite regional reductions of IL-5 and IL-10 as well as local reductions of TNF-alpha, MCP-1, MCP-3, and eotaxin. Thus, the type 2 granuloma was not converted to a type 1 composition with IL-4 knockout, but showed persistent expression of IL-13 and some degree of IL-5 and MCP-3, suggesting that these cytokines could potentially support a compensatory type 2 response. IFN-gamma knockout did not augment type 2 granuloma size or Th2 cytokines in lymph nodes and unexpectedly reduced IL-4 transcripts in lungs. This study offers important implications regarding inflammation and its relationship to local and regional cytokine expression.

Mycobacterial and schistosomal antigen-elicited granuloma formation in IFN-gamma and IL-4 knockout mice: analysis of local and regional cytokine and chemokine networks

Type 1 (IFN-gamma/TNF-dominant) and 2 (IL-4/IL-5-dominant) granulomatous inflammation were analyzed in mice with knockout of IFN-gamma or IL-4 genes. Lung granulomas were elicited by beads coated with purified protein derivative (PPD) of Mycobacteria bovis or soluble Schistosoma mansoni egg Ags. Parameters included granuloma size, composition, and macrophage function; white blood cell differentials; lymph node cytokine profiles; and cytokine/chemokine mRNA expression by lungs. Type 1 (PPD) and 2 (soluble Schistosoma mansoni egg Ags) responses showed characteristic cytokine and chemokine profiles in control mice. IFN-gamma knockout converted the PPD response to a type 2-like pattern with eosinophil infiltration and decreased TNF and RANTES, but increased IL-4, IL-5, IL-10, IL-13, monocyte chemoattractant protein-3 (MCP-3), and eotaxin expression. IL-4 knockout exacerbated type 1 inflammation with increased IL-2/IFN-gamma production by lymph nodes and IL-1 production by granuloma macrophages, but unexpectedly, IFN-gamma transcripts were reduced in lungs. Regarding the type 2 response, IL-4 was needed for maximal blood eosinophilia, but surprisingly, its absence had a minimal effect on type 2 granuloma size and composition despite regional reductions of IL-5 and IL-10 as well as local reductions of TNF-alpha, MCP-1, MCP-3, and eotaxin. Thus, the type 2 granuloma was not converted to a type 1 composition with IL-4 knockout, but showed persistent expression of IL-13 and some degree of IL-5 and MCP-3, suggesting that these cytokines could potentially support a compensatory type 2 response. IFN-gamma knockout did not augment type 2 granuloma size or Th2 cytokines in lymph nodes and unexpectedly reduced IL-4 transcripts in lungs. This study offers important implications regarding inflammation and its relationship to local and regional cytokine expression.

The role of chemokines in inflammatory joint disease

Rheumatoid arthritis (RA) is an autoimmune disease characterized by the elicitation and activation of a number of leukocyte populations within both the synovial space and joint tissue. The recruited leukocytes subsequently play an instrumental role in synovial cell proliferation, pannus formation, and bone erosion. Although it is know that leukocytes are important participants in the evolving joint pathology, the mechanism responsible for the successful elicitation of cells to the joint is not clear. A number of studies have identified an association of specific cytokines, including chemokines, with active arthritis, but longitudinal analyses of cytokine expression and the causal role of these mediators have not been defined. Animal models and cell culture systems have proved useful in identifying the expression of various cytokines during the maintenance of chronic joint inflammation. In addition, animal models have provided important information regarding the kinetic production and contribution of specific mediators to the development of experimental arthritis. These studies provide insights into the potential mechanisms for leukocyte involvement in inflammatory joint disease.

Expression and biology of neutrophil and endothelial cell-derived chemokines

The elicitation of polymorphonuclear leukocytes or neutrophils to an area of tissue injury is one of the most fundamental of all cell responses during the initiation of host defense. Historically, the neutrophil has been identified as an important phagocytic cell with a limited capacity to synthesize de-novo proteins. However, recent investigations have now shown that stimulated neutrophils can express a variety of cytokines, such as tumor necrosis factor, interleukin-1, interferon-alpha and interleukin-8. The ability of neutrophils and endothelial cells to produce interleukin-8 is extremely important, as this chemokine can contribute to the continued maintenance of cell infiltrates into the developing inflammatory lesion.

CD8+ and CD45RA+ human peripheral blood lymphocytes are potent sources of macrophage inflammatory protein 1 alpha, interleukin-8 and RANTES

The chemokines macrophage inflammatory protein 1 alpha (MIP 1 alpha), interleukin-8 (IL-8) and RANTES are potent regulators of leukocyte trafficking. Examination of chemokine secretion by human peripheral blood lymphocytes after stimulation with anti-CD3 or phorbol 12, 13 myristate acetate and ionomycin showed CD8+ cells were the dominant source of MIP 1 alpha and RANTES. Although production of MIP 1 alpha and IL-8 were similar in pharmacologically stimulated CD4+ CD45RA+, CD4+ CD45RO+, and CD8+ CD45RA+ cells, the largest amounts of MIP 1 alpha and RANTES were secreted by CD8+ CD45RO+ lymphocytes. A parallel pattern of prolonged chemokine mRNA expression for at least 18 h after activation was observed in the T cells subsets. These results confirm that human T lymphocytes have a unique capacity for secretion of these three chemokines. In addition, CD8+ cells have an unrecognized role in recruiting cells to sites of inflammation, and adult human CD45RA+ cells have a physiologically significant secretory capacity.

Chemokines and their role in human disease

The recruitment of leukocyte populations to an area of inflammation is one of the most fundamental processes of immune reactivity, yet a number of the mechanisms which are important to this process are not clearly understood. Investigations directed at understanding the mechanisms of leukocyte elicitation have centered around classical chemotactic factors such as C5a and fMLP, however, these known agents have demonstrated little specificity for recruiting particular leukocyte populations. Recent advances in this field have been made with the discovery of a novel supergene family of chemotactic cytokines or chemokines. These cytokines are important as they possess a high degree of specificity for the recruitment of specific subpopulations of leukocytes.