IL-17 controls central nervous system autoimmunity through the intestinal microbiome

Interleukin-17A- (IL-17A) and IL-17F-producing CD4(+) T helper cells (T(H)17 cells) are implicated in the development of chronic inflammatory diseases, such as multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE). T-H 17 cells also orchestrate leukocyte invasion of the central nervous system (CNS) and subsequent tissue damage. However, the role of IL-17A and IL-17F as effector cytokines is still confused with the encephalitogenic function of the cells that produce these cytokines, namely, T-H 17 cells, fueling a long-standing debate in the neuroimmunology field. Here, we demonstrated that mice deficient for IL-17A/F lose their susceptibility to EAE, which correlated with an altered composition of their gut microbiota. However, loss of IL-17A/F in T-H cells did not diminish their encephalitogenic capacity. Reconstitution of a wild-type-like intestinal microbiota or reintroduction of IL-17A specifically into the gut epithelium of IL-17A/F-deficient mice reestablished their susceptibility to EAE. Thus, our data demonstrated that IL-17A and IL-17F are not encephalitogenic mediators but rather modulators of intestinal homeostasis that indirectly alter CNS-directed autoimmunity.

Mice from a genetically resistant background lacking the interferon gamma receptor are susceptible to infection with Leishmania major but mount a polarized T helper cell 1-type CD4+ T cell response

Michel Aguet

Mice with homologous disruption of the gene coding for the ligand-binding chain of the interferon (IFN) gamma receptor and derived from a strain genetically resistant to infection with Leishmania major have been used to study further the role of this cytokine in the differentiation of functional CD4+ T cell subsets in vivo and resistance to infection. Wild-type 129/Sv/Ev mice are resistant to infection with this parasite, developing only small lesions, which resolve spontaneously within 6 wk. In contrast, mice lacking the IFN-gamma receptor develop large, progressing lesions. After infection, lymph nodes (LN) and spleens from both wild-type and knockout mice showed an expansion of CD4+ cells producing IFN-gamma as revealed by measuring IFN-gamma in supernatants of specifically stimulated CD4+ T cells, by enumerating IFN-gamma-producing T cells, and by Northern blot analysis of IFN-gamma transcripts. No biologically active interleukin (IL) 4 was detected in supernatants of in vitro-stimulated LN or spleen cells from infected wild-type or deficient mice. Reverse transcription polymerase chain reaction analysis with primers specific for IL-4 showed similar IL-4 message levels in LN from both types of mice. The IL-4 message levels observed were comparable to those found in similarly infected C57BL/6 mice and significantly lower than the levels found in BALB/c mice. Anti-IFN-gamma treatment of both types of mice failed to alter the pattern of cytokines produced after infection. These data show that even in the absence of IFN-gamma receptors, T helper cell (Th) 1-type responses still develop in genetically resistant mice with no evidence for the expansion of Th2 cells.

1995

Mice lacking the IFN-gamma receptor have impaired ability to resolve a lung eosinophilic inflammatory response associated with a prolonged capacity of T cells to exhibit a Th2 cytokine profile

Michel Aguet

To investigate the modulatory role of IFN-gamma on the induction and maintenance of Th2 mucosal immunity in vivo, experiments were performed in mice lacking the IFN-gamma R. Aerosol OVA challenge of immunized wild-type mice resulted in an infiltration of eosinophils into the lung, associated with the ex vivo production of Th2 cytokines (IL-4 and IL-5) from purified lung Thy1.2+ cells stimulated via the CD3/TCR complex. However, while immunized IFN-gamma R-deficient mice exhibited elevated levels of IgE, IgG1, and reduced levels of IgG2a compared with wild-type mice, there was no difference in the recruitment of eosinophils into the lung or the production of IL-4 and IL-5 from lung T cells on day 3. In contrast, up to 2 mo after a single Ag challenge, eosinophils were still present in the lungs of IFN-gamma R-deficient, but not wild-type, mice. Likewise, lung-derived T cells from IFN-gamma R-deficient mice produced higher levels of IL-4 and IL-5, both at 1 and 2 mo after OVA challenge compared with T cells from wild-type mice. We conclude that endogenous IFN-gamma regulates the humoral isotype Ab pattern, but does not modulate the commitment of T cells to a Th2 phenotype in vivo or the acute infiltration of eosinophils to the lung. However, in the absence of IFN-gamma-mediated signaling, there is a transition from a spontaneously resolving to a persisting eosinophilic inflammation of the lungs, associated with a sustained capacity of lung T cells to secrete a Th2 cytokine profile.

1996

Establishment of polarized microglial cells derived from mouse embryonic stem cells

Céline Ruegsegger

Microglia are the resident immune cells of the central nervous system (CNS). Microglia undergo rapid activation in response to even minor pathological changes in the CNS. The activation state of microglia and tissue macrophages is characterized by two extremes that are known as M1 and M2. M1 is triggered upon pro-inflammatory stimuli and lead to the secretion of molecules involved in brain defense but also in neurotoxicity. M2 arises upon anti-inflammatory stimuli and is hallmarked by the secretion of molecules that mediate tolerance and neuroprotection. The aim of this study was to investigate the in vitro polarization capacity of microglia into M1 and M2 subtypes. Primary microglia are hard to obtain in sufficient number and therefore a recently developed protocol was applied to differentiate microglial precursors from mouse embryonic stem (ES) cells. The obtained ES cell derived microglial precursors (ESdM) were shown to be an appropriate substitute to primary microglia. Here we showed that ESdM stimulated with interferon-γ (IFN-gamma) and lipopolysaccharide (LPS) display typical M1 characteristics like higher transcription levels of pro-inflammatory cytokines as well as an increase in the expression level of M1 surface markers. They also secreted significantly higher levels of the chemokine CXCL10 and nitric oxide than untreated or interleukin-4 (IL-4) treated cells. These results indicate that ESdM can be polarized into a cytotoxic subtype in vitro using IFN-gamma and LPS. However, no evidence indicating that ESdM were polarized into a neuroprotective M2 subtype by IL-4 treatment has been found. Even though an increase in the transcription level of anti-inflammatory cytokines was observed upon IL-4 treatment, this increase was not significant. In addition, no increase in the expression levels of M2 markers or in the secretion of the anti-inflammatory cytokine IL-10 were found upon IL-4 treatment indicating that IL-4 might be insufficient to polarize ESdM into M2 subtype in vitro. Further experiments are required to better understand the mechanisms of microglial sub-differentiation and to determine the stability of the acquired M1 and M2 phenotypes over time

2010

Establishment of polarized microglial cells derived from mouse embryonic stem cells

Céline Ruegsegger

2010