Protective role of IFN-gamma in collagen-induced arthritis conferred by inhibition of mycobacteria-induced granulocyte chemotactic protein-2 production.

Mice with a disrupted IFN-gamma system are remarkably susceptible to experimental autoimmune diseases, such as collagen-induced arthritis (CIA), which rely on the use of CFA. The inflammatory lesions of these IFN-gamma knockout (KO) mice are characterized by an excessive proportion of neutrophils. Here, we show that the increased severity of CIA in IFN-gammaR KO as compared with wild-type mice is accompanied by increased levels of the CXC chemokine granulocyte chemotactic protein-2 (GCP-2), a major neutrophil-attracting chemokine in mice. We demonstrated that the heat-killed mycobacteria present in CFA elicited production of GCP-2 in mouse embryo fibroblast cultures and that this production was inhibited by IFN-gamma. Inhibition of GCP-2 production by IFN-gamma was STAT-1-dependent. IFN-gamma receptor KO mice treated with neutralizing anti-GCP-2 antibodies were protected from CIA, indicating the in vivo importance of GCP-2 in the pathogenesis of CIA. Our data support the notion that one of the mechanisms whereby endogenous IFN-gamma mitigates the manifestations of CIA consists of inhibiting production of GCP-2, thereby limiting mobilization and infiltration of neutrophils, which are important actors in joint inflammation. These results may also be applicable to other experimental models of autoimmunity that rely on the use of CFA.

Neutralization of IL-17C Reduces Skin Inflammation in Mouse Models of Psoriasis and Atopic Dermatitis.

IL-17C is a functionally distinct member of the IL-17 family that was believed to play a role in the pathogenesis of psoriasis. Here we confirmed that IL-17C is involved in psoriasis and explored potential roles for IL-17C in atopic dermatitis (AD). An anti-IL-17C antibody, MOR106, was generated that potently and selectively binds to human and mouse IL-17C, thereby inhibiting the binding of IL-17C to its IL-17RE receptor. The antibody inhibited cutaneous inflammation in an IL-23-induced psoriatic-like skin inflammation model. In lesional skin of patients with AD, IL-17C expression levels were increased and localized to keratinocytes and infiltrating immune cells. To determine the contribution of IL-17C to AD pathogenesis, MOR106 was tested in two distinct in vivo models. In the calcipotriol-induced AD model, ear skin inflammation, TSLP, and IL-33 protein production in ears was suppressed by MOR106. Consistently, in the flaky tail strain mouse model, spontaneous development of AD-like skin inflammation was reduced by MOR106. Moreover, serum IgE levels, number of mast cells in skin and T helper type 2-related cytokines IL-4 and CCL17 in serum were all reduced. Overall, our results indicate that IL-17C is a central mediator of skin inflammation beyond psoriasis and is relevant in particular in AD.

Freund's complete adjuvant induces arthritis in mice lacking a functional interferon-gamma receptor by triggering tumor necrosis factor alpha-driven osteoclastogenesis.

OBJECTIVE: To investigate the hypothesis that Freund's complete adjuvant (CFA) plays an essential role in the induction of collagen-induced arthritis in mice, by testing whether CFA by itself is able to induce arthritis in interferon-gamma receptor-knockout (IFNgammaR-KO) mice. METHODS: IFNgammaR-KO and wild-type mice were sensitized with a single intradermal injection of CFA containing heat-killed Mycobacterium butyricum. Flow cytometric analysis and in vitro osteoclastogenesis assays were performed on blood, spleen, and bone marrow cells. Tumor necrosis factor (TNF) levels were measured in the serum, and levels of RANKL, osteoprotegerin (OPG), and TNFalpha in the synovium were determined by quantitative reverse transcriptase-polymerase chain reaction. Effects of treatment with the TNFalpha antagonist etanercept were assessed. RESULTS: Symptoms of arthritis appeared in IFNgammaR-KO mice but not in wild-type mice, and reached an incidence of 55%. The onset coincided with an expansion of CD11b+ splenocytes that spontaneously produced TNFalpha and with increased osteoclastogenesis in spleen and blood cells. Expansion of CD11b+ splenocytes and osteoclast precursor cells was more pronounced in arthritic than in nonarthritic mice. There was a >100-fold increase in the RANKL:OPG ratio in the synovia of CFA-sensitized mice compared with those of naive animals. Treatment with etanercept prevented the development of arthritis and mitigated the increased expansion of myeloid cells as well as the increase in osteoclast precursor numbers in the spleen and blood. CONCLUSION: These results indicate that sensitization of mice with CFA creates a condition in which dysregulation of a single cytokine leads to arthritis by triggering TNFalpha-driven osteoclastogenesis.

Defective CD4+CD25+ regulatory T cell functioning in collagen-induced arthritis: an important factor in pathogenesis, counter-regulated by endogenous IFN-gamma.

Mice with a deficiency in IFN-gamma or IFN-gamma receptor (IFN-gammaR) are more susceptible to collagen-induced arthritis (CIA), an experimental autoimmune disease that relies on the use of complete Freund's adjuvant (CFA). Here we report that the heightened susceptibility of IFN-gammaR knock-out (KO) mice is associated with a functional impairment of CD4+CD25+ Treg cells. Treatment of wild-type mice with depleting anti-CD25 antibody after CFA-assisted immunisation with collagen type II (CII) significantly accelerated the onset of arthritis and increased the severity of CIA. This is an indication of a role of Treg cells in the effector phase of CIA. IFN-gammaR deficiency did not affect the number of CD4+CD25+ T cells in the central and peripheral lymphoid tissues. In addition, CD4+CD25+ T cells isolated from naive IFN-gammaR KO mice had a normal potential to suppress T cell proliferation in vitro. However, after immunisation with CII in CFA, the suppressive activity of CD4+CD25+ T cells became significantly more impaired in IFN-gammaR-deficient mice. Moreover, expression of the mRNA for Foxp3, a highly specific marker for Treg cells, was lower. We further demonstrated that the effect of endogenous IFN-gamma, which accounts for more suppressive activity in wild-type mice, concerns both Treg cells and accessory cells. Our results demonstrate that the decrease in Treg cell activity in CIA is counter-regulated by endogenous IFN-gamma.