InVivoMAb anti-mouse Ly6G/Ly6C (Gr-1)

Bullous pemphigoid (BP) and epidermolysis bullosa acquisita are subepidermal autoimmune blistering diseases mediated by autoantibodies against type XVII collagen (Col17) and Col7, respectively. For blister formation, Fc-mediated events, such as infiltration of inflammatory cells in the skin, complement activation, and release of proteases at the dermal-epidermal junction, are essential. Although in the neonatal passive transfer mouse model of BP, tissue destruction is mediated by Fcgamma receptors (FcgammaRs) I and III, the passive transfer model of epidermolysis bullosa acquisita completely depends on FcgammaRIV. To clarify this discrepancy, we developed a novel experimental model for BP using adult mice. Lesion formation was Fc mediated because gamma-chain-deficient mice and mice treated with anti-Col17 IgG, depleted from its sugar moiety at the Fc portion, were resistant to disease induction. By the use of various FcgammaR-deficient mouse strains, tissue destruction was shown to be mediated by FcgammaRIV, FcgammaRIII, and FcgammaRIIB, whereas FcgammaRI was not essential. Furthermore, anti-inflammatory mediators in already clinically diseased mice can be explored in the novel BP model, because the pharmacological inhibition of FcgammaRIV and depletion of granulocytes abolished skin blisters. Herein, we extended our knowledge about the importance of FcgammaRs in experimental BP and established a novel BP mouse model suitable to study disease development over a longer time period and explore novel treatment strategies in a quasi-therapeutic setting.

T-bet(-/-).Rag2(-/-) (TRUC) mice spontaneously develop microbiota-driven, TNF-mediated large bowel inflammation that resembles human ulcerative colitis. We show here that IL-23 and IL-1-dependent secretion of IL-17A by innate lymphoid cells (ILCs; defined as CD45(+)lin(-)Thy1(hi)NKp46(-)) is a second critical pathway in this model. Using an in vitro coculture system of bone marrow-derived dendritic cells (DCs) and freshly isolated FACS-purified ILCs, we demonstrate that IL-23 and IL-1 secreted by DCs in response to microbial stimulation work together to induce IL-17A production by ILCs. TNF is not required for IL-17A secretion by ILCs in vitro but synergizes with IL-17A to induce the expression of neutrophil-attracting chemokines. Upstream, activation of the IL-23/IL-17A axis is regulated by nucleotide-binding oligomerization domain containing (Nod)/receptor-interacting serine-threonine kinase 2 (Ripk2) signals in DCs. Genetic ablation of the Nod/Ripk2 signaling pathway protects TRUC mice from developing colitis without affecting the colitogenicity of the intestinal microbiota. Our data provide insight into the complex network of interactions between IL-17A-secreting ILCs and other components of the innate immune system in the development of colitis.

Psoriasis (Ps) and psoriasis arthritis (PsA) are poorly understood common diseases, induced by unknown environmental factors, affecting skin and articular joints. A single i.p. exposure to mannan from Saccharomyces cerevisiae induced an acute inflammation in inbred mouse strains resembling human Ps and PsA-like disease, whereas multiple injections induced a relapsing disease. Exacerbation of disease severity was observed in mice deficient for generation of reactive oxygen species (ROS). Interestingly, restoration of ROS production, specifically in macrophages, ameliorated both skin and joint disease. Neutralization of IL-17A, mainly produced by gammadelta T cells, completely blocked disease symptoms. Furthermore, mice depleted of granulocytes were resistant to disease development. In contrast, certain acute inflammatory mediators (C5, Fcgamma receptor III, mast cells, and histamine) and adaptive immune players (alphabeta T and B cells) were redundant in disease induction. Hence, we propose that mannan-induced activation of macrophages leads to TNF-alpha secretion and stimulation of local gammadelta T cells secreting IL-17A. The combined action of activated macrophages and IL-17A produced in situ drives neutrophil infiltration in the epidermis and dermis of the skin, leading to disease manifestations. Thus, our finding suggests a new mechanism triggered by exposure to exogenous microbial components, such as mannan, that can induce and exacerbate Ps and PsA.

Influenza and bacterial coinfection is a significant cause of hospitalization and death in humans during influenza epidemics and pandemics. However, the fundamental protective and pathogenic mechanisms involved in this complex virus-host-bacterium interaction remain incompletely understood. In this study, we have developed mild to lethal influenza and Streptococcus pneumoniae coinfection models for comparative analyses of disease pathogenesis. Specifically, wild-type and IL-1R type 1-deficient (Il1r1(-/-) ) mice were infected with influenza virus and then superchallenged with noninvasive S. pneumoniae serotype 14 (Spn14) or S. pneumoniae serotype 19A (Spn19A). The coinfections were followed by comparative analyses of inflammatory responses and animal protection. We found that resident alveolar macrophages are efficient in the clearance of both pneumococcal serotypes in the absence of influenza infection; in contrast, they are essential for airway control of Spn14 infection but not Spn19A infection. In agreement, TNF-alpha and neutrophils play a compensatory protective role in secondary bacterial infection associated with Spn19A; however, the essential requirement for alveolar macrophage-mediated clearance significantly enhances the virulence of Spn14 during postinfluenza pneumococcal infection. Furthermore, we show that, although IL-1 signaling is not required for host defense against pneumococcal infection alone, it is essential for sustaining antibacterial immunity during postinfluenza pneumococcal infection, as evidenced by significantly aggravated bacterial burden and animal mortality in Il1r1(-/-) mice. Mechanistically, we show that through preventing alveolar macrophage depletion, inflammatory cytokine IL-1 signaling is critically involved in host resistance to influenza and pneumococcal coinfection.