TLR9 in peritoneal B-1b cells is essential for production of protective self-reactive IgM to control Th17 cells and severe autoimmunity.

The role of TLR9 in the development of the autoimmune disease systemic lupus erythematosus is controversial. In different mouse models of the disease, loss of TLR9 abolishes the generation of anti-nucleosome IgG autoantibodies but at the same time exacerbates lupus disease. However, the TLR9-dependent tolerance mechanism is unknown. In this study, we show that loss of TLR9 is associated with low peritoneal B-1b cell numbers and low levels of protective self-reactive IgM serum autoantibodies in lupus-prone FcγRIIB-deficient mice leading to the uncontrolled accumulation of proinflammatory CD4(+) cells and exacerbated autoimmunity. TLR7 signaling was not able to compensate for the loss of TLR9 signaling in peritoneal B-1b cells to induce IgM Abs. Transfer of TLR9-expressing peritoneal B-1b cells from FcγRIIB-deficient mice or of recombinant monoclonal self-reactive IgM Abs was sufficient to reduce the frequency of proinflammatory Th17 cells and lupus disease in FcγRIIB/TLR9 double-deficient mice. Taken together, these data provide evidence for a TLR9-dependent tolerance mechanism of peritoneal B-1b cells generating protective self-reactive IgM in lupus-prone mice to control Th17 cell development and severe autoimmunity.

Tolerance induction with T cell-dependent protein antigens induces regulatory sialylated IgGs.

BACKGROUND: Under inflammatory conditions, T cell-dependent (TD) protein antigens induce proinflammatory T- and B-cell responses. In contrast, tolerance induction by TD antigens without costimulation triggers the development of regulatory T cells. Under both conditions, IgG antibodies are generated, but whether they have different immunoregulatory functions remains elusive. OBJECTIVE: It was shown recently that proinflammatory or anti-inflammatory effector functions of IgG molecules are determined by different Fc N-linked glycosylation patterns. We sought to examine the Fc glycosylation and anti-inflammatory quality of IgG molecules formed on TD tolerance induction. METHODS: We administered chicken ovalbumin (OVA) with or without costimulus to mice and analyzed OVA-reactive IgG Fc glycosylation. The anti-inflammatory function of differentially glycosylated anti-OVA IgGs was further investigated in studies with dendritic cell cultures and in an in vivo model of allergic airway disease. Additionally, we analyzed the Fc glycosylation pattern of birch pollen-reactive serum IgGs after successful allergen-specific immunotherapy in patients. RESULTS: Stimulation with TD antigens under inflammatory conditions induces plasma cells expressing low levels of α2,6-sialyltransferase and producing desialylated IgGs. In contrast, plasma cells induced on tolerance induction did not downregulate α2,6-sialyltransferase expression and secreted immunosuppressive sialylated IgGs that were sufficient to block antigen-specific T- and B-cell responses, dendritic cell maturation, and allergic airway inflammation. Importantly, successful specific immunotherapy in allergic patients also induced sialylated allergen-specific IgGs. CONCLUSIONS: Our data show a novel antigen-specific immunoregulatory mechanism mediated by anti-inflammatory sialylated IgGs that are formed on TD tolerance induction. These findings might help to develop novel antigen-specific therapies for the treatment of allergy and autoimmunity.

Managing the patent thicket and maximizing patent lifetime in vaccine technology.

Patents are exclusive rights for a limited period of time that are granted to provide an incentive for innovation and in exchange for the public disclosure of an invention. Patenting in the medical field, especially in the field of human vaccine technologies, is full of pitfalls, because the products that finally access the market are often covered by a multitude of exclusive IP rights. This commentary gives an overview on obstacles in vaccine patenting and how to overcome them, and intends to provide a patenting guideline for researchers.

Sialylated Autoantigen-Reactive IgG Antibodies Attenuate Disease Development in Autoimmune Mouse Models of Lupus Nephritis and Rheumatoid Arthritis.

Pro- and anti-inflammatory effector functions of IgG antibodies (Abs) depend on their subclass and Fc glycosylation pattern. Accumulation of non-galactosylated (agalactosylated; G0) IgG Abs in the serum of rheumatoid arthritis and systemic lupus erythematosus (SLE) patients reflects severity of the diseases. In contrast, sialylated IgG Abs are responsible for anti-inflammatory effects of the intravenous immunoglobulin (pooled human serum IgG from healthy donors), administered in high doses (2 g/kg) to treat autoimmune patients. However, whether low amounts of sialylated autoantigen-reactive IgG Abs can also inhibit autoimmune diseases is hardly investigated. Here, we explore whether sialylated autoantigen-reactive IgG Abs can inhibit autoimmune pathology in different mouse models. We found that sialylated IgG auto-Abs fail to induce inflammation and lupus nephritis in a B cell receptor (BCR) transgenic lupus model, but instead are associated with lower frequencies of pathogenic Th1, Th17 and B cell responses. In accordance, the transfer of small amounts of immune complexes containing sialylated IgG Abs was sufficient to attenuate the development of nephritis. We further showed that administration of sialylated collagen type II (Col II)-specific IgG Abs attenuated the disease symptoms in a model of Col II-induced arthritis and reduced pathogenic Th17 cell and autoantigen-specific IgG Ab responses. We conclude that sialylated autoantigen-specific IgG Abs may represent a promising tool for treating pathogenic T and B cell immune responses in autoimmune diseases.

T cell-independent B cell activation induces immunosuppressive sialylated IgG antibodies.

Antigen-specific Abs are able to enhance or suppress immune responses depending on the receptors that they bind on immune cells. Recent studies have shown that pro- or antiinflammatory effector functions of IgG Abs are also regulated through their Fc N-linked glycosylation patterns. IgG Abs that are agalactosylated (non-galactosylated) and asialylated are proinflammatory and induced by the combination of T cell-dependent (TD) protein antigens and proinflammatory costimulation. Sialylated IgG Abs, which are immunosuppressive, and Tregs are produced in the presence of TD antigens under tolerance conditions. T cell-independent (TI) B cell activation via B cell receptor (BCR) crosslinking through polysaccharides or via BCR and TLR costimulation also induces IgG Abs, but the Fc glycosylation state of these Abs is unknown. We found in mouse experiments that TI immune responses induced suppressive sialylated IgGs, in contrast to TD proinflammatory Th1 and Th17 immune responses, which induced agalactosylated and asialylated IgGs. Transfer of low amounts of antigen-specific sialylated IgG Abs was sufficient to inhibit B cell activation and pathogenic immune reactions. These findings suggest an immune regulatory function for TI immune responses through the generation of immunosuppressive sialylated IgGs and may provide insight on the role of TI immune responses during infection, vaccination, and autoimmunity.

Development of self-reactive germinal center B cells and plasma cells in autoimmune Fc gammaRIIB-deficient mice.

Abnormalities in expression levels of the IgG inhibitory Fc gamma receptor IIB (FcγRIIB) are associated with the development of immunoglobulin (Ig) G serum autoantibodies and systemic autoimmunity in mice and humans. We used Ig gene cloning from single isolated B cells to examine the checkpoints that regulate development of autoreactive germinal center (GC) B cells and plasma cells in FcγRIIB-deficient mice. We found that loss of FcγRIIB was associated with an increase in poly- and autoreactive IgG(+) GC B cells, including hallmark anti-nuclear antibody-expressing cells that possess characteristic Ig gene features and cells producing kidney-reactive autoantibodies. In the absence of FcγRIIB, autoreactive B cells actively participated in GC reactions and somatic mutations contributed to the generation of highly autoreactive IgG antibodies. In contrast, the frequency of autoreactive IgG(+) B cells was much lower in spleen and bone marrow plasma cells, suggesting the existence of an FcγRIIB-independent checkpoint for autoreactivity between the GC and the plasma cell compartment.