Active participation of antigen-nonspecific lymphoid cells in immune-mediated inflammation

Alpha4 beta7 integrin controls Th17 cell trafficking in the spinal cord leptomeninges during experimental autoimmune encephalomyelitis

Th1 and Th17 cell migration into the central nervous system (CNS) is a fundamental process in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), the animal model of multiple sclerosis (MS). Particularly, leptomeningeal vessels of the subarachnoid space (SAS) constitute a central route for T cell entry into the CNS during EAE. Once migrated into the SAS, T cells show an active motility behavior, which is a prerequisite for cell-cell communication, in situ reactivation and neuroinflammation. However, the molecular mechanisms selectively controlling Th1 and Th17 cell trafficking in the inflamed leptomeninges are not well understood. By using epifluorescence intravital microscopy, we obtained results showing that myelin-specific Th1 and Th17 cells have different intravascular adhesion capacity depending on the disease phase, with Th17 cells being more adhesive at disease peak. Inhibition of αLβ2 integrin selectively blocked Th1 cell adhesion, but had no effect on Th17 rolling and arrest capacity during all disease phases, suggesting that distinct adhesion mechanisms control the migration of key T cell populations involved in EAE induction. Blockade of α4 integrins affected myelin-specific Th1 cell rolling and arrest, but only selectively altered intravascular arrest of Th17 cells. Notably, selective α4β7 integrin blockade inhibited Th17 cell arrest without interfering with intravascular Th1 cell adhesion, suggesting that α4β7 integrin is predominantly involved in Th17 cell migration into the inflamed leptomeninges in EAE mice. Two-photon microscopy experiments showed that blockade of α4 integrin chain or α4β7 integrin selectively inhibited the locomotion of extravasated antigen-specific Th17 cells in the SAS, but had no effect on Th1 cell intratissue dynamics, further pointing to α4β7 integrin as key molecule in Th17 cell trafficking during EAE development. Finally, therapeutic inhibition of α4β7 integrin at disease onset by intrathecal injection of a blocking antibody attenuated clinical severity and reduced neuroinflammation, further demonstrating a crucial role for α4β7 integrin in driving Th17 cell-mediated disease pathogenesis. Altogether, our data suggest that a better knowledge of the molecular mechanisms controlling myelin-specific Th1 and Th17 cell trafficking during EAE delevopment may help to identify new therapeutic strategies for CNS inflammatory and demyelinating diseases.

Type I Interferon Therapy Limits CNS Autoimmunity by Inhibiting CXCR3-Mediated Trafficking of Pathogenic Effector T Cells

Type I interferons (IFNs) have therapeutic potential in CNS autoimmune diseases, such as uveitis, but the molecular mechanisms remain unclear. Using a T cell-transfer model of experimental autoimmune uveitis (EAU), we found that IFN-α/β treatment inhibited the migration of IFN-γ-producing pathogenic CD4⁺ T cells to effector sites. IFN-α/β upregulated the expression of the cognate ligands CXCL9, CXCL10, and CXCL11, causing ligand-mediated downregulation of CXCR3 expression and effector T cell retention in the spleen. Accordingly, type I IFN did not alter EAU progression in CXCR3^-/- mice. In uveitis patients, disease exacerbations correlated with reduced serum IFN-α concentrations. IFN-α/β reduced CXCR3 expression and migration by human effector T cells, and these parameters were associated with the therapeutic efficacy of IFN-α in uveitis patients. Our findings provide insight into the molecular basis of type I IFN therapy for CNS autoimmune diseases and identify CXCR3 as a biomarker for effective type I IFN immunotherapy.

Neuroimmune Mechanisms of Depression in Adults with Heart Failure

Heart failure (HF) is a major and costly public health concern, and its prognosis is grim-with high hospitalization and mortality rates. HF affects millions of individuals across the world, and this condition is expected to become "the epidemic" of the twenty-first century (Jessup et al., 2016). It is well documented that individuals with HF experience disproportionately high rates of depression and that those who are depressed have worse clinical outcomes than their nondepressed counterparts. The purpose of this chapter is to introduce the reader to the study of depression in HF, and how psychoneuroimmunologic principles have been applied to further elucidate mechanisms (i.e., neurohormonal and cytokine activation) linking these comorbid disorders.

Phenotypes of Th lineages generated by the commonly used activation with anti-CD3/CD28 antibodies differ from those generated by the physiological activation with the specific antigen

T-helper (Th) lineages have been generated in vitro by activating CD4 cells with anti-CD3/CD28 antibodies during polarization. Physiologically, however, the generation of Th lineages is by activation with the specific antigen presented by antigen-presenting cells (APC). Here, we used T-cell receptor (TCR)-transgenic mice to compare the phenotypes of Th1, Th9 and Th17 lineages when generated by either one of the two activation modes. Lineage Th cells specific against hen egg lysozyme (HEL), were adoptively transferred into recipient mice transgenically expressing HEL in their lens. Remarkable differences were found between lineages of Th1, Th9 or Th17, generated by either one of the two modes in their capacities to migrate to and proliferate in the recipient spleen and, importantly, to induce inflammation in the recipient mouse eyes. Substantial differences were also observed between the lineage pairs in their transcript expression profiles of certain chemokines and chemokine receptors. Surprisingly, however, close similarities were observed between the transcript expression profiles of lineages of the three phenotypes, activated by the same mode. Furthermore, Th cell lineages generated by the two activation modes differed considerably in their pattern of gene expression, as monitored by microarray analysis, but exhibited commonality with lineages of other phenotypes generated by the same activation mode. This study thus shows that (i) Th lineages generated by activation with anti-CD3/CD28 antibodies differ from lineages generated by antigen/APC; and (ii) the mode of activation determines to a large extent the expression profile of major transcripts.

Neuroimmune mechanisms of depression in heart failure

Heart failure (HF) is a major and costly public health concern, and its prognosis is grim-with high hospitalization and mortality rates. It is well documented that HF patients experience disproportionately high rates of depression and that depressed HF patients have worse clinical outcomes than their non-depressed counterparts. The purpose of this chapter is to introduce the reader to the study of depression in HF, and how psychoneuroimmunologic principals have been applied to further elucidate the mechanisms (i.e., neurohormonal and cytokine activation) linking these co-morbid disorders.

In situ recognition of autoantigen as an essential gatekeeper in autoimmune CD8+ T cell inflammation

A current paradigm states that non-antigen-specific inflammatory cues attract noncognate, bystander T cell specificities to sites of infection and autoimmune inflammation. Here we show that cues emanating from a tissue undergoing spontaneous autoimmune inflammation cannot recruit naive or activated bystander T cell specificities in the absence of local expression of cognate antigen. We monitored the recruitment of CD8(+) T cells specific for the prevalent diabetogenic epitope islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP)(206-214) in gene-targeted nonobese diabetic (NOD) mice expressing a T cell "invisible" IGRP(206-214) sequence. These mice developed islet inflammation and diabetes with normal incidence and kinetics, but their inflammatory lesions could recruit neither naive (endogenous or exogenous) nor ex vivo-activated IGRP(206-214)-reactive CD8(+) T cells. Conversely, IGRP(206-214)-reactive, but not nonautoreactive CD8(+) T cells rapidly homed to and accumulated in the inflamed islets of wild-type NOD mice. Our results indicate that CD8(+) T cell recruitment to a site of autoimmune inflammation results from an active process that is strictly dependent on local display of cognate pMHC and suggest that CD8(+) T cells contained in extralymphoid autoimmune lesions are largely autoreactive.

Unlike Th1, Th17 cells mediate sustained autoimmune inflammation and are highly resistant to restimulation-induced cell death

Both Th1 and Th17 T cell subsets can mediate inflammation, but the kinetics of the pathogenic processes mediated by these two subsets have not been investigated. Using an experimental system in which TCR-transgenic Th1 or Th17 cells specific for hen egg lysozyme induce ocular inflammation in recipient mice expressing eye-restricted hen egg lysozyme, we found important differences in the in vivo behavior of these two subsets. Th1 cells initially proliferated considerably faster and invaded the eye more quickly than their Th17 counterparts, but then disappeared rapidly. By contrast, Th17 cells accumulated and remained the majority of the infiltrating CD4(+) cells in the eye for as long as 25 days after transfer, mediating more long-lasting pathological changes. Unlike Th1, Th17 cells were highly resistant to restimulation-induced apoptosis, a major pathway by which autoimmune and chronically restimulated Th1 cells are eliminated. Th17 cells had reduced Fas ligand production and resistance to Fas-induced apoptosis, relative to Th1 cells, despite similar surface expression of Fas. Th17-induced ocular inflammation also differed from Th1-induced inflammation by consisting of more neutrophils, whereas Th1-induced disease had higher proportions of CD8 cells. Taken together, our data show that pathogenic processes triggered by Th17 lag behind those induced by Th1, but then persist remarkably longer, apparently due to the relative resistance of Th17 cells to restimulation-induced cell death. The long-lasting inflammation induced by Th17 cells is in accord with these cells being involved in chronic conditions in humans.

A potential shift from adaptive immune activity to nonspecific inflammatory activation associated with higher depression symptoms in chronic heart failure patients

BACKGROUND

Chronic heart failure (CHF) patients with elevated depression symptoms are at greater risk of morbidity and mortality. The mechanisms linking symptoms of depression with disease progression in CHF are unclear. However, research studies have found evidence of alterations in immune activity associated with depression symptoms that may influence heart function. The present study sought to determine the relationship between depression symptoms and chemotaxis of peripheral blood mononuclear cells (PBMCs) in CHF patients, both at rest and in response to moderate exercise.

METHODS AND RESULTS

Sixty-five patients diagnosed with CHF (mean age, 59.8 +/- 14.5 years) and 45 non-CHF control subjects (mean age, 52.1 +/- 11.6) completed the Beck Depression Inventory (BDI) before undergoing a moderate 20-minute bicycle exercise task. Chemotaxis of PBMCs was examined in vitro to a bacterial peptide f-met leu phe (fMLP) and a physiologic chemokine, stromal cell derived factor-1 (SDF-1) immediately before and after exercise. CHF patients had reduced chemotaxis to SDF-1 (P = .025) compared with non-CHF subjects. Higher BDI scores were associated with reduced baseline chemotaxis to SDF-1 in both CHF and non-CHF subjects (P = .027). In contrast, higher BDI scores were associated with increased chemotaxis to fMLP (P = .049) and SDF-1 (P = .018) in response to exercise in the CHF patients.

CONCLUSION

The present study suggests a shift in immune cell mobility in CHF patients with greater depression symptom severity, with reduced chemotaxis to a physiologically specific chemokine at rest but increased chemotaxis to both nonspecific and specific chemical attractants in response to physical activity. This could have implications for cardiac repair and remodeling in CHF patients and therefore may affect disease progression.

Flexible low-cost system for small animal aerosol inhalation exposure to drugs, proteins, inflammatory agents, and infectious agents

The design for a simple, low-cost aerosol generation system for rodent inhalation studies is described here. This system is appropriate for low biohazard–level agents. In this study, two biosafety level 2 agents, Pasturella pneumotropica and Pseudomonas aeruginosa, were tested successfully. This system was also used to immunize mice and guinea pigs in ovalbumin-based models of pulmonary inflammation. This design is appropriate for studies with limited budgets and lower-level biosafety containment.

Phenotype switching by inflammation-inducing polarized Th17 cells, but not by Th1 cells

Th1 and Th17 cells are characterized by their expression of IFN-gamma or IL-17, respectively. The finding of Th cells producing both IL-17 and IFN-gamma suggested, however, that certain Th cells may modify their selective cytokine expression. In this study, we examined changes in cytokine expression in an experimental system in which polarized Th1 or Th17 cells specific against hen egg lysozyme induce ocular inflammation in recipient mice expressing hen egg lysozyme in their eyes. Whereas only IFN-gamma was expressed in eyes of Th1 recipient mice, substantial proportions of donor cells expressed IFN-gamma or both IFN-gamma and IL-17 in Th17 recipient eyes. The possibility that nonpolarized cells in Th17 preparations were responsible for expression of IFN-gamma or IFN-gamma/IL-17 in Th17 recipient eyes was contradicted by the finding that the proportions of such cells were larger in recipients of Th17 preparations with 20-25% nonpolarized cells than in recipients of 35-40% preparations. Moreover, whereas incubation in vitro of Th1 cells with Th17-polarizing mixture had no effect on their phenotype, incubation of Th17 with Th1-polarizing mixture, or in the absence of cytokines, converted most of these cells into IFN-gamma or IFN-gamma/IL-17-expressing cells. In addition, Th17 incubated with the Th1 mixture expressed T-bet, whereas no ROR-gamma t was detected in Th1 incubated with Th17 mixture. Thus, polarized Th1 cells retain their phenotype in the tested systems, whereas Th17 may switch to express IFN-gamma or IFN-gamma/IL-17 following activation in the absence of cytokines, or exposure to certain cytokine milieus at the inflammation site or in culture.

The sentinel node technique is useful for studies of intestinal immunology in inflammatory bowel disease patients

OBJECTIVE

Mesenteric lymph nodes may play a crucial role in the pathogenesis of human inflammatory bowel disease. We have used the sentinel node technique to analyze mesenteric lymph nodes draining inflammatory lesions sentinel nodes and corresponding site of inflamed bowel in patients with ulcerative colitis or Crohn's disease.

METHODS

Thirty-two patients undergoing surgical treatment of inflammatory bowel disease were included. Sentinel nodes were identified intraoperatively. The T cells were harvested from the mesenteric lymph nodes and characterized by flow cytometry.

RESULTS

The distribution of CD4CD62L (homing-marked) and CD4CD69 (activated) T cells was studied in mesenteric lymph nodes draining inflammation, nodes draining normal intestine, blood, and mucosa. The turnover of T cells was markedly increased in the lymph nodes connected to inflammatory segments. The immunologic activity of the sentinel lymph nodes correlated with the degree of intestinal inflammation.

CONCLUSION

Mesenteric sentinel nodes provide important information about locoregional immunology and pathogenesis in inflammatory bowel disease.

Both Th1 and Th17 are immunopathogenic but differ in other key biological activities

The role of Th17 lymphocytes in immunopathogenic processes has been well established, but little is known about their basic cell features. In this study, we compared polarized Th1 and Th17 for key biological activities related to pathogenicity and trafficking. Th1 and Th17 lineages were derived from TCR-transgenic CD4 murine cells specific against hen egg lysozyme. When adoptively transferred into mice expressing hen egg lysozyme in their eyes, both Th1 and Th17 induced ocular inflammation but with slight differences in histological pathology. PCR analysis revealed selective expression of IFN-gamma or IL-17 in eyes of Th1 or Th17 recipients, respectively. Additionally, Th1 and Th17 were found to differ in three other key activities: 1) Th17 cells were inferior to Th1 cells in their capacity to trigger massive lymphoid expansion and splenomegaly; 2) the proportion of Th1 cells among infiltrating cells in inflamed recipient eyes declined rapidly, becoming a minority by day 7, whereas Th17 cells remained in the majority throughout this period; and 3) remarkable differences were noted between Th1 and Th17 cells in their expression of certain surface markers. In particular, reactivated Th1 expressed higher levels of CD49d and alpha(4)beta(7) (mucosal homing) in vitro and higher levels of CXCR3 (Th1 trafficking) in vivo. Reactivated Th17, however, expressed higher levels of alpha(E)beta(7) (epithelial tissue homing) and CD38 (activation, maturation and trafficking) in vitro, but in vivo Th17 expressed higher levels of alpha(4)beta(7) and CCR6 (lymphocyte trafficking). These data reveal that Th1 and Th17 cells differ in several key biological activities influencing migration and pathogenic behavior during inflammatory disease.

Microbial products trigger autoimmune ocular inflammation

PURPOSE

Microbial products stimulate the immune system by interacting with Toll-like receptors (TLR) on antigen-presenting cells. This study examined the hypothesis that microbial products, which function as TLR ligands, are playing a major role in triggering pathogenic autoimmunity.

METHODS

An experimental system was developed in which microbial TLR ligands were tested in vivo for their capacity to stimulate naïve CD4 cells specific against hen egg lysozyme (HEL) to become effector cells capable of inducing inflammation in eyes in which HEL is expressed. The ligands' mode of action was analyzed by determining their effects on the proliferation, acquisition of tissue-invading capacity, i.e. elevated CD49d and decreased CD62L expression, and production of interferon-gamma by the HEL-specific cells.

RESULTS

All the 7 tested TLR ligands triggered ocular inflammation in the experimental system used here, with pertussis toxin surpassing all other ligands in its activities. A correlation was found between the capacity of the ligands to trigger pathogenic immunity and to stimulate the proliferation, modification of cell surface and interferon-gamma production by T cells.

CONCLUSIONS

This study provides direct evidence to support the notion that microbial products are capable of triggering pathogenic autoimmunity.