In vivo induction of Tr1 cells via mucosal dendritic cells and AHR signaling.

BACKGROUND: Type 1 regulatory T (Tr1) cells, characterized by the secretion of high levels of the anti-inflammatory cytokine interleukin-10 (IL-10), play an important role in the regulation of autoimmune diseases and transplantation. However, effective strategies that specifically induce Tr1 cells in vivo are limited. Furthermore, the pathways controlling the induction of these cells in vivo are not well understood. METHODOLOGY/PRINCIPAL FINDINGS: Here we report that nasal administration of anti-CD3 antibody induces suppressive Tr1 cells in mice. The in vivo induction of Tr1 cells by nasal anti-CD3 is dependent on IL-27 produced by upper airway resident dendritic cells (DCs), and is controlled by the transcription factors aryl hydrocarbon receptor (AHR) and c-Maf. Subsequently, IL-21 acts in an autocrine fashion to expand and maintain the Tr1 cells induced in vivo by nasally administered anti-CD3. CONCLUSIONS/SIGNIFICANCE: Our findings identify a unique approach to generate Tr1 cells in vivo and provide insights into the mechanisms by which these cells are induced.

Mucosal anti-CD3 monoclonal antibody attenuates collagen-induced arthritis that is associated with induction of LAP+ regulatory T cells and is enhanced by administration of an emulsome-based Th2-skewing adjuvant.

Mucosal (nasal or oral) administration of anti-CD3 mAb is effective in ameliorating animal models of autoimmunity (experimental autoimmune encephalomyelitis, diabetes, and lupus) by inducing LAP(+) regulatory T cells. We tested this approach in an arthritis model using type II collagen. We found that nasal anti-CD3 was more effective than oral anti-CD3 in attenuating the development of arthritis. Nasal anti-CD3 induced a LAP(+) regulatory T cell that secreted high levels of IL-10 and suppressed collagen-specific T cell proliferation and anti-collagen Ab production. However, neither nasal nor oral anti-CD3 attenuated disease when given to animals with ongoing arthritis, and this was associated with a lack of induction of LAP(+) regulatory T cells. We found, however, that coadministration of a novel emulsome adjuvant, which enhances Th2 responses, resulted in the induction of LAP(+) regulatory T cells and suppression of ongoing arthritis by both nasal and oral anti-CD3. Suppression of arthritis by mucosal anti-CD3 was associated with less joint damage, a decrease of TNF-alpha and IFN-gamma mRNA expression in joints, and a reduction in anti-collagen Abs. These results demonstrate that mucosal anti-CD3 therapy may serve as a therapeutic approach in arthritis and that the biologic effect is enhanced by an emulsome-based adjuvant.

Induction of regulatory T cells decreases adipose inflammation and alleviates insulin resistance in ob/ob mice.

Leptin-deficient ob/ob mice are overweight, develop insulin resistance, and serve as a model for type 2 diabetes (T2D). Studies suggest that inflammatory pathways are linked to the development of insulin resistance and T2D both in animals and humans. We asked whether the induction of regulatory T cells (Tregs) could alleviate the pathological and metabolic abnormalities in ob/ob mice. We induced TGF-beta-dependent CD4(+) latency-associated peptide (LAP)-positive Tregs by oral administration of anti-CD3 antibody plus beta-glucosylceramide. We found a decrease in pancreatic islet cell hyperplasia, fat accumulation in the liver, and inflammation in adipose tissue, accompanied by lower blood glucose and liver enzymes. In addition, treated animals had decreased CD11b(+)F4/80(+) macrophages and TNF-alpha in adipose tissue. Adoptive transfer of orally induced CD4(+)LAP(+) Tregs ameliorated metabolic and cytokine abnormalities. Our results demonstrate the importance of inflammation in T2D and identify a unique immunological approach for treatment of T2D by the induction of Tregs.

Induction of mucosal tolerance in SLE: a sniff or a sip away from ameliorating lupus?

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by aberrant immune responses against intracellularly derived self antigens. Treatment for SLE relies on the use of aggressive immunosuppressants and steroids that are nonspecific and can cause serious adverse effects. The observation that a systemic immune tolerance to self antigens or generation of regulatory T cells may follow mucosal (nasal or oral) exposure to self proteins or monoclonal antibody against CD3 respectively suggests that induction of mucosal tolerance offers the basis of a side effect-free therapy that could re-establish the ability to distinguish self from non-self and restore peripheral tolerance in individuals susceptible to developing autoimmune diseases. Here I review studies on mucosal tolerance in autoimmune diseases and discuss the therapeutic potential of inducing tolerance for the treatment of SLE.

Nasal anti-CD3 antibody ameliorates lupus by inducing an IL-10-secreting CD4+ CD25- LAP+ regulatory T cell and is associated with down-regulation of IL-17+ CD4+ ICOS+ CXCR5+ follicular helper T cells.

Lupus is an Ab-mediated autoimmune disease. One of the potential contributors to the development of systemic lupus erythematosus is a defect in naturally occurring CD4(+)CD25(+) regulatory T cells. Thus, the generation of inducible regulatory T cells that can control autoantibody responses is a potential avenue for the treatment of systemic lupus erythematosus. We have found that nasal administration of anti-CD3 mAb attenuated lupus development as well as arrested ongoing lupus in two strains of lupus-prone mice. Nasal anti-CD3 induced a CD4(+)CD25(-)latency-associated peptide (LAP)(+) regulatory T cell that secreted high levels of IL-10 and suppressed disease in vivo via IL-10- and TFG-beta-dependent mechanisms. Disease suppression also occurred following adoptive transfer of CD4(+)CD25(-)LAP(+) regulatory T cells from nasal anti-CD3-treated animals to lupus-prone mice. Animals treated with nasal anti-CD3 had less glomerulonephritis and diminished levels of autoantibodies as measured by both ELISA and autoantigen microarrays. Nasal anti-CD3 affected the function of CD4(+)ICOS(+)CXCR5(+) follicular helper T cells that are required for autoantibody production. CD4(+)ICOS(+)CXCR5(+) follicular helper T cells express high levels of IL-17 and IL-21 and these cytokines were down-regulated by nasal anti-CD3. Our results demonstrate that nasal anti-CD3 induces CD4(+)CD25(-)LAP(+) regulatory T cells that suppress lupus in mice and that it is associated with down-regulation of T cell help for autoantibody production.

The mechanism of nasal tolerance in lupus prone mice is T-cell anergy induced by immature B cells that lack B7 expression.

To determine if B cells of lupus prone NZB mice possess intrinsic defects that directly lead or contribute to T-cell hyper-responsiveness, we injected age-, sex- and MHC II-matched NZB and Balb/c mice with histone peptide H471 representing a dominant Th cell epitope in histone H4 of the nucleosome. We found that B220+ B cells of NZB mice express high levels of surface CD86 following antigen priming. We cocultured CD4+ T and B220+ B cells of naïve or peptide primed NZB and Balb/c mice in the presence of peptide. Antigen presentation by autoimmune B cells of NZB mice induced hyper-responsiveness from normal CD4+ T cells of Balb/c mice. T-cell hyper-responsiveness is a result of CD86 costimulation by B cells of NZB mice. Induction of nasal tolerance to H471 in NZB mice suppressed CD86 surface expression and led to downregulation of T-cell proliferative response and cytokine production. More interestingly, B220+ B cells from nasally tolerized NZB mice induced T-cell anergy to anti-CD3 and anti-CD28 antibody stimulation in vitro. The anergic T cells do not possess suppressive function in coculture with naïve responder T cells nor produce suppressive cytokines interleukin 10 and transforming growth factor-beta in vitro.

Oral tolerance.

Autoimmune conditions caused by injurious immune responses against self-antigens can be ameliorated if the inappropriate responses to self-components that cause tissue injury can be modulated by regulatory cells or shut off via the induction of anergy or via deletion of pathogenic immune responses. Antigen encounter at the gut mucosa can lead to suppression of injurious immune responses to self-antigen via these mechanisms. This type of immunological event is termed oral tolerance. In this review, we examine the mechanisms behind the induction of oral tolerance and provide findings from its use as a form of treatment for autoimmune diseases.

Histone peptide-induced nasal tolerance: suppression of murine lupus.

Induced mucosal tolerance has been shown to be beneficial in preventing or treating a number of murine and human autoimmune disorders. However, this particular form of therapy has not been thoroughly tested in systemic lupus erythematosus. In this study, we investigated the conditions for induction of nasal tolerance using a histone peptide named H471 expressing a dominant T cell epitope in the histone protein H4 of mononucleosome in lupus-prone SNF(1) female mice. We also tested the effect of chronic peptide nasal treatment on the development of autoimmune reactivities in these mice. Results demonstrated that a dose-dependent nasal tolerance to peptide H471 can be achieved before or after peptide sensitization in SNF(1) mice. In addition, tolerance to mononucleosomes was induced by nasal instillation of SNF(1) mice with H471. This was accompanied by an increase in IL-10 and suppression of IFN-gamma production by lymph node cells. Suppression of Th1-type cytokines was also observed in SNF(1) mice that were nasally administered with H471 before intradermal injection with the peptide. Finally, chronic nasal instillation of mice with the H471 peptide not only suppressed the development of autoantibodies, but also altered the severity of glomerulonephritis in lupus-prone SNF(1) mice.