Pathogenesis of lupus-like nephritis through autoimmune antibody produced by CD180-negative B lymphocytes in NZBWF1 mouse. Immunol Lett. 2012;144:1-6. [PMID: 22387632 DOI: 10.1016/j.imlet.2012.02.012]

Human RP105 monoclonal antibody enhances antigen-specific antibody production in unique culture conditions

Detecting antibodies, particularly those targeting donor human leukocyte antigens in organ transplantation and self-antigens in autoimmune diseases, is crucial for diagnosis and therapy. Radioprotective 105 (RP105), a Toll-like receptor family protein, is expressed in immune-competent cells, such as B cells. Studies in mice have shown that the anti-mouse RP105 antibody strongly activates B cells and triggers an adjuvant effect against viral infections. However, the anti-human RP105 antibody (ɑhRP105) weakly activates human B cells. This study established new culture conditions under, which human B cells are strongly activated by the ɑhRP105. When combined with CpGDNA, specific antibody production against blood group carbohydrates, ɑGal, and SARS-CoV-2 was successfully detected in human B cell cultures. Furthermore, comprehensive analysis using liquid chromatography-electrospray ionization tandem mass spectrometry, single-cell RNA sequencing, and quantitative real-time PCR revealed that ɑhRP105 triggered a different activation stimulus compared to CpGDNA. These findings could help identify antibody-producing B cells in cases of transplant rejection and autoimmune diseases.

Irradiation Attenuates Systemic Lupus Erythematosus-Like Morbidity in NZBWF1 Mice: Focusing on CD180-Negative Cells

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the production of autoantibodies that can induce systemic inflammation. Ultraviolet-A and X-ray irradiation have been reported to have therapeutic effects in patients with SLE. We previously demonstrated that CD180-negative cells, these are radiosensitive, contribute to the development of SLE-like morbidity in NZBWF1 mice. In this study, the effects of irradiation on SLE-like morbidity manifestations in NZBWF1 mice and on CD180-negative cells were investigated. Whole-body irradiation, excluding the head, attenuated SLE-like morbidity in vivo, as indicated by the prevention of the renal lesion development, inhibition of anti-dsDNA antibody production, reduction of urinary protein levels, and prolongation of the lifespan. Irradiation also reduced the proportion of CD180-negative cells in the spleen. Although other immune cells or molecules may be triggered because of the whole-body irradiation treatment, previous research, and the current results suggest a strong relationship between the radiation-induced decrease in CD180-negative cells and the amelioration of SLE-like morbidities. Clinical trials assessing CD180-negative cells as a therapeutic target for SLE have been hampered by the lack of validated cell markers; nonetheless, the present findings suggest that radiotherapy may be a new therapeutic strategy for managing SLE symptoms.

The role of CD180 in hematological malignancies and inflammatory disorders

Toll-like receptors play a significant role in the innate immune system and are also involved in the pathophysiology of many different diseases. Over the past 35 years, there have been a growing number of publications exploring the role of the orphan toll-like receptor, CD180. We therefore set out to provide a narrative review of the current evidence surrounding CD180 in both health and disease. We first explore the evidence surrounding the role of CD180 in physiology including its expression, function and signaling in antigen presenting cells (APCs) (dendritic cells, monocytes, and B cells). We particularly focus on the role of CD180 as a modulator of other TLRs including TLR2, TLR4, and TLR9. We then discuss the role of CD180 in inflammatory and autoimmune diseases, as well as in hematological malignancies of B cell origin, including chronic lymphocytic leukemia (CLL). Based on this evidence we produce a current model for CD180 in disease and explore the potential role for CD180 as both a prognostic biomarker and therapeutic target. Throughout, we highlight specific areas of research which should be addressed to further the understanding of CD180 biology and the translational potential of research into CD180 in various diseases.

Cell surface expression of human RP105 depends on N-glycosylation of MD-1

For its cell surface expression, radioprotective 105 (RP105) - an orphan Toll-like receptor - must form a complex with a soluble glycoprotein called myeloid differentiation 1 (MD-1). The number of RP105-negative cells is significantly increased in patients with systemic lupus erythematosus (SLE); however, to elucidate the mechanism underlying this increase, how RP105 is expressed on the cell surface depending on MD-1 should be investigated. We demonstrated that RP105 exhibits two forms depending on MD-1 and its two N-glycosylation sites, N96 and N156. Cell surface expression of RP105 decreased in the presence of mutant MD-1 (N96Q/N156Q). Nonglycosylated MD-1 decreased the de novo cell surface expression of RP105 but not pre-expressed RP105. Thus, the N-glycans of MD-1 may represent targets for SLE therapy.

Toll-Like Receptor Homolog CD180 Expression Is Diminished on Natural Autoantibody-Producing B Cells of Patients with Autoimmune CNS Disorders

Purpose

Decreased expression of TLR homolog CD180 in peripheral blood B cells and its potential role in antibody production have been described in autoimmune diseases. Effectiveness of anti-CD20 therapy in neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS) strengthens the role of B cells in the pathogenesis. Therefore, we aimed to investigate the CD180 expression of peripheral blood B cell subsets in NMOSD and MS patients and analyze the levels of natural anti-citrate synthase (CS) IgG autoantibodies and IgG antibodies induced by bacterial infections reported to play a role in the pathogenesis of NMOSD or MS.

Methods

We analyzed the distribution and CD180 expression of peripheral blood B cell subsets, defined by CD19/CD27/IgD staining, and measured anti-CS IgM/G natural autoantibody and antibacterial IgG serum levels in NMOSD, RRMS, and healthy controls (HC).

Results

We found decreased naïve and increased memory B cells in NMOSD compared to MS. Among the investigated four B cell subsets, CD180 expression was exclusively decreased in CD19⁺CD27⁺IgD⁺ nonswitched (NS) memory B cells in both NMOSD and MS compared to HC. Furthermore, the anti-CS IgM natural autoantibody serum level was lower in both NMOSD and MS. In addition, we found a tendency of higher anti-CS IgG natural autoantibody levels only in anti-Chlamydia IgG antibody-positive NMOSD and MS patients.

Conclusions

Our results suggest that reduced CD180 expression of NS B cells could contribute to the deficient natural IgM autoantibody production in NMOSD and MS, whereas natural IgG autoantibody levels show an association with antibacterial antibodies.

Toll-Like Receptor Mediated Activation of Natural Autoantibody Producing B Cell Subpopulations in an Autoimmune Disease Model

Altered expression and function of the Toll-like receptor (TLR) homologue CD180 molecule in B cells have been associated with autoimmune disorders. In this study, we report decreased expression of CD180 at protein and mRNA levels in peripheral blood B cells of diffuse cutaneous systemic sclerosis (dcSSc) patients. To analyze the effect of CD180 stimulation, together with CpG (TLR9 ligand) treatment, on the phenotype defined by CD19/CD27/IgD/CD24/CD38 staining, and function (CD69 and CD180 expression, cytokine and antibody secretion) of B cell subpopulations, we used tonsillar B cells. After stimulation, we found reduced expression of CD180 protein and mRNA in total B cells, and CD180 protein in B cell subpopulations. The frequency of CD180+ cells was the highest in the CD19+CD27+IgD+ non-switched (NS) B cell subset, and they showed the strongest activation after anti-CD180 stimulation. Furthermore, B cell activation via CD180 induced IL-6 and natural autoantibody secretion. Treatment with the combination of anti-CD180 antibody and CpG resulted in increased IL-6 and IL-10 secretion and natural autoantibody production of B cells. Our results support the role of CD180 in the induction of natural autoantibody production, possibly by NS B cells, and suggest an imbalance between the pathologic and natural autoantibody production in SSc patients.

Ligation of CD180 inhibits IFN-α signaling in a Lyn-PI3K-BTK-dependent manner in B cells

A hallmark of systemic lupus erythematosus (SLE) is the consistent production of various auto-antibodies by auto-reactive B cells. Interferon-α (IFN-α) signaling is highly activated in SLE B cells and plays a vital role in the antibody response by B cells. Previous studies have shown that CD180-negative B cells, which are dramatically increased in SLE patients, are responsible for the production of auto-antibodies. However, the association between CD180 and IFN-α signaling remains unknown. In the present study, we explored the effect of CD180 on regulating the activation of IFN-α signaling in B cells. We found that the number of CD180-negative B cells was increased in MRL/Mp-Fas(lpr/lpr) lupus-prone mice compared with wild-type mice. Phenotypic analysis showed that CD180-negative B cells comprised CD138+ plasmablast/plasma cells and GL-7+ germinal center (GC) B cells. Notably, ligation of CD180 significantly inhibited the IFN-α-induced phosphorylation of signal transducer and activator of transcription 2 (STAT-2) and expression of IFN-stimulated genes (ISGs) in a Lyn-PI3K-BTK-dependent manner in vitro. Moreover, ligation of CD180 could also inhibit IFN-α-induced ISG expression in B cells in vivo. Furthermore, the Toll-like receptor 7 and Toll-like receptor 9 signaling pathways could significantly downregulate CD180 expression and modulate the inhibitory effect of CD180 signaling on the activation of IFN-α signaling. Collectively, our results highlight the close association between the increased proportion of CD180-negative B cells and the activation of IFN-α signaling in SLE. Our data provide molecular insight into the mechanism of IFN-α signaling activation in SLE B cells and a potential therapeutic approach for SLE treatment.

Roles of plasmablasts in IgG4-related disease and various immune-based diseases

IgG4-related disease (IgG4-RD) is a systemic fibro-inflammatory disease with multiple organ disorders. Recently, in IgG4-RD, increased circulating plasmablasts have been found. The subsets of plasmablasts are negative for RP105 (CD180). A large population of B cells lacking RP105 (RP105-negative B cells) are found in patients with active with systemic lupus erythematosus and other systemic autoimmune diseases, including dermatomyositis, and Sjögren’s syndrome. In other conditions, such as neuromyelitis optica, Kawasaki’s disease, primary biliary cirrhosis and aging, RP105 expression on B cells and monocytes also alters. We review the basic science and clinical significance of RP105-negative B cells including plasmablasts in various immune-based diseases. RP105-negative B cells, especially plasmablasts, play crucial roles in both systemic and organ-specific autoimmune and inflammatory disorders.

Roles of B Cell-Intrinsic TLR Signals in Systemic Lupus Erythematosus

Toll-like receptors (TLRs) are a large family of pattern recognition receptors. TLR signals are involved in the pathogenesis of systemic lupus erythematosus. Mouse and human B cells constitutively express most TLRs. Many B cell subpopulations are highly responsive to certain TLR ligation, including B-1 B cells, transitional B cells, marginal zone B cells, germinal center B cell and memory B cells. The B cell-intrinsic TLR signals play critical roles during lupus process. In this review, roles of B cell-intrinsic TLR2, 4, 7, 8 and 9 signals are discussed during lupus pathogenesis in both mouse model and patients. Moreover, mechanisms underlying TLR ligation-triggered B cell activation and signaling pathways are highlighted.

TLR2 and TLR4 in autoimmune diseases: a comprehensive review

Autoimmune diseases are immune disorders characterized by T cell hyperactivity and B cell overstimulation leading to overproduction of autoantibodies. Although the pathogenesis of various autoimmune diseases remains to be elucidated, environmental factors have been thought to contribute to the initiation and maintenance of auto-respond inflammation. Toll-like receptors (TLRs) are pattern recognition receptors belonging to innate immunity that recognize and defend invading microorganisms. Besides these exogenous pathogen-associated molecular patterns, TLRs can also bind with damage-associated molecular patterns produced under strike or by tissue damage or cells apoptosis. It is believed that TLRs build a bridge between innate immunity and autoimmunity. There are five adaptors to TLRs including MyD88, TRIF, TIRAP/MAL, TRAM, and SARM. Upon activation, TLRs recruit specific adaptors to initiate the downstream signaling pathways leading to the production of inflammatory cytokines and chemokines. Under certain circumstances, ligation of TLRs drives to aberrant activation and unrestricted inflammatory responses, thereby contributing to the perpetuation of inflammation in autoimmune diseases. In the past, most studies focused on the intracellular TLRs, such as TLR3, TLR7, and TLR9, but recent studies reveal that cell surface TLRs, especially TLR2 and TLR4, also play an essential role in the development of autoimmune diseases and afford multiple therapeutic targets. In this review, we summarized the biological characteristics, signaling mechanisms of TLR2/4, the negative regulators of TLR2/4 pathway, and the pivotal function of TLR2/4 in the pathogenesis of autoimmune diseases including rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, Sjogren's syndrome, psoriasis, multiple sclerosis, and autoimmune diabetes.

Increased RP105-Negative B Cells in IgG4-Related Disease

Four patients with IgG4-related disease (IgG4-RD) showed increased percentages of RP105-negative B cells in the peripheral blood. Case 1: A 66-year-old man having retroperitoneal fibrosis had 18.8% of RP105-negative B cells. Oral prednisolone improved the affected lesions and the percentage of RP105-negative B cells decreased (3.2%) after the treatment. Case 2: A 53-year-old man with retroperitoneal fibrosis had 27.9% of RP105-negative B cells. Case 3: A 38-year-old man with follicular hyperplasia showed increased percentage of RP105-negative B cells (8.3%). Case 4: A 60-year-old man with interstitial nephritis had 27.5% of RP105-negative B cells. The treatment decreased the numbers of RP105-negative B cells. Increased numbers of RP105-negatvie B cells is possibly associated with disease activity of IgG4-RD. Analysis of expression of RP105 on B cells may be helpful in evaluation of disease activity of IgG4-RD.

A soft coral-derived compound, 11-epi-sinulariolide acetate suppresses inflammatory response and bone destruction in adjuvant-induced arthritis

In recent years, a significant number of metabolites with potent anti-inflammatory properties have been discovered from marine organisms, and several of these compounds are now under clinical trials. In the present study, we isolated 11-epi-sinulariolide acetate (Ya-s11), a cembrane-type compound with anti-inflammatory effects, from the Formosa soft coral Sinularia querciformis. Preliminary screening revealed that Ya-s11 significantly inhibited the expression of the proinflammatory proteins induced nitric oxide synthase and cyclooxygenase-2 in lipopolysaccharide-stimulated murine macrophages. We also examined the therapeutic effects of Ya-s11 on adjuvant-induced arthritis (AIA) in female Lewis rats, which demonstrate features similar to human rheumatoid arthritis (RA). Animal experiments revealed that Ya-s11 (subcutaneously 9 mg/kg once every 2 days from day 7 to day 28 postimmunization) significantly inhibited AIA characteristics. Moreover, Ya-s11 also attenuated protein expression of cathepsin K, matrix metalloproteinases-9 (MMP-9), tartrate-resistant acid phosphatase (TRAP), and tumor necrosis factor-α (TNF-α) in ankle tissues of AIA-rats. Based on its attenuation of the expression of proinflammatory proteins and disease progression in AIA rats, the marine-derived compound Ya-s11 may serve as a useful therapeutic agent for the treatment of RA.

Soft coral-derived lemnalol alleviates monosodium urate-induced gouty arthritis in rats by inhibiting leukocyte infiltration and iNOS, COX-2 and c-Fos protein expression

An acute gout attack manifests in the joint as dramatic inflammation. To date, the clinical use of medicinal agents has typically led to undesirable side effects. Numerous efforts have failed to create an effective and safe agent for the treatment of gout. Lemnalol—an extract from Formosan soft coral—has documented anti-inflammatory and anti-nociceptive properties. In the present study, we attempt to examine the therapeutic effects of lemnalol on intra-articular monosodium urate (MSU)-induced gouty arthritis in rats. In the present study, we found that treatment with lemnalol (intramuscular [im]), but not colchicine (oral [po]), significantly attenuated MUS-induced mechanical allodynia, paw edema and knee swelling. Histomorphometric and immunohistochemistry analysis revealed that MSU-induced inflammatory cell infiltration, as well as the elevated expression of c-Fos and pro-inflammatory proteins (inducible nitric oxide synthase and cyclooxygenase-2) observed in synovial tissue, were significantly inhibited by treatment with lemnalol. We conclude that lemnalol may be a promising candidate for the development of a new treatment for gout and other acute neutrophil-driven inflammatory diseases.