APRIL in B-cell malignancies and autoimmunity

Anti-inflammatory role of APRIL by modulating regulatory B cells in antigen-induced arthritis

APRIL (A Proliferation-Inducing Ligand), a member of the TNF superfamily, was initially described for its ability to promote proliferation of tumor cells in vitro. Moreover, this cytokine has been related to the pathogenesis of different chronic inflammatory diseases, such as rheumatoid arthritis. This study aimed to evaluate the ability of APRIL in regulating B cell-mediated immune response in the antigen-induced arthritis (AIA) model in mice. AIA was induced in previously immunized APRIL-transgenic (Tg) mice and their littermates by administration of antigen (mBSA) into the knee joints. Different inflammatory cell populations in spleen and draining lymph nodes were analyzed using flow cytometry and the assay was performed in the acute and chronic phases of the disease, while cytokine levels were assessed by ELISA. In the acute AIA, APRIL-Tg mice developed a less severe condition and a smaller inflammatory infiltrate in articular tissues when compared with their littermates. We also observed that the total cellularity of draining lymph nodes was decreased in APRIL-Tg mice. Flow cytometry analysis revealed an increase of CD19+IgM+CD5+ cell population in draining lymph nodes and an increase of CD19+CD21hiCD23hi (B regulatory) cells in APRIL-Tg mice with arthritis as well as an increase of IL-10 and CXCL13 production in vitro.

Assessment of Corneal Epithelial Changes and Related Factors in Ocular Chronic Graft-Versus-Host Disease (GVHD) by in Vivo Confocal Microscopy

PURPOSE

To evaluate corneal epithelial changes and related factors in chronic ocular graft-versus-host disease (oGVHD) patients.

METHODS

21 patients (35 eyes) with chronic oGVHD and 8 patients (12 eyes) without oGVHD after bone marrow transplantation were recruited for assessment involving in vivo confocal microscopy (IVCM) analysis, ocular surface parameter determination and tear cytokine level analysis. The IVCM corneal epithelial scoring system was used to evaluate corneal epithelial changes.

RESULTS

There was a significant difference in the corneal epithelial score (p = .001) between the two groups. The corneal epithelial scores were significantly correlated with the corneal fluorescein staining scores (CFS, r = 0.463, p < .001), Schirmer's test (r = -0.389, p = .009) and tear cytokine levels of EGF (r = -0.491, p < .001) and APRIL (r = -0.318, p = .030).

CONCLUSIONS

The depth of corneal epithelial defects can be estimated by the CFS. Corneal epithelial changes of chronic oGVHD are considered to be associated with lacrimal deficiency and a lack of EGF.

Desmoglein-Specific B-Cell-Targeted Single-Cell Analysis Revealing Unique Gene Regulation in Patients with Pemphigus

Autoreactive B cells are assumed to play a critical role in pemphigus; however, the characteristics of these cells are not yet fully understood. In this study, 23 pemphigus vulgaris or pemphigus foliaceus samples were used to isolate circulating desmoglein (DSG)-specific B cells. Transcriptome analysis of the samples was performed at the single-cell level to detect genes involved in disease activity. DSG1- or DSG3-specific B cells from three patients' differentially expressed genes related to T cell costimulation (CD137L) as well as B-cell differentiation (CD9, BATF, TIMP1) and inflammation (S100A8, S100A9, CCR3), compared with nonspecific B cells from the same patients. When the DSG1-specific B cells before and after treatment transcriptomes of the patient with pemphigus foliaceus were compared, there were changes in several B-cell activation pathways not detected in non-DSG1-specific B cells. This study clarifies the transcriptomic profile of autoreactive B cells in patients with pemphigus and documents the gene expression related to disease activity. Our approach can be applied to other autoimmune diseases and has the potential for future detection of disease-specific autoimmune cells.

Lymphoid stromal cells - potential implications for the pathogenesis of CVID

Non-hematopoietic lymphoid stromal cells (LSC) maintain lymph node architecture and form niches allowing the migration, activation, and survival of immune cells. Depending on their localization in the lymph node, these cells display heterogeneous properties and secrete various factors supporting the different activities of the adaptive immune response. LSCs participate in the transport of antigen from the afferent lymph as well as in its delivery into the T and B cell zones and organize cell migration via niche-specific chemokines. While marginal reticular cells (MRC) are equipped for initial B-cell priming and T zone reticular cells (TRC) provide the matrix for T cell-dendritic cell interactions within the paracortex, germinal centers (GC) only form when both T- and B cells successfully interact at the T-B border and migrate within the B-cell follicle containing the follicular dendritic cell (FDC) network. Unlike most other LSCs, FDCs are capable of presenting antigen via complement receptors to B cells, which then differentiate within this niche and in proximity to T follicular helper (T_FH) cells into memory and plasma cells. LSCs are also implicated in maintenance of peripheral immune tolerance. In mice, TRCs induce the alternative induction of regulatory T cells instead of T_FH cells by presenting tissue-restricted self-antigens to naïve CD4 T cells via MHC-II expression. This review explores potential implications of our current knowledge of LSC populations regarding the pathogenesis of humoral immunodeficiency and autoimmunity in patients with autoimmune disorders or common variable immunodeficiency (CVID), the most common form of primary immunodeficiency in humans.

Advanced Molecular Dynamics Approaches to Model a Tertiary Complex APRIL/TACI with Long Glycosaminoglycans

Glycosaminoglycans (GAGs) are linear anionic periodic polysaccharides participating in a number of biologically relevant processes in the extracellular matrix via interactions with their protein targets. Due to their periodicity, conformational flexibility, pseudo-symmetry of the sulfation pattern, and the key role of electrostatics, these molecules are challenging for both experimental and theoretical approaches. In particular, conventional molecular docking applied for GAGs longer than 10-mer experiences severe difficulties. In this work, for the first time, 24- and 48-meric GAGs were docked using all-atomic repulsive-scaling Hamiltonian replica exchange molecular dynamics (RS-REMD), a novel methodology based on replicas with van der Waals radii of interacting molecules being scaled. This approach performed well for proteins complexed with oligomeric GAGs and is independent of their length, which distinguishes it from other molecular docking approaches. We built a model of long GAGs in complex with a proliferation-inducing ligand (APRIL) prebound to its receptors, the B cell maturation antigen and the transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI). Furthermore, the prediction power of the RS-REMD for this tertiary complex was evaluated. We conclude that the TACI–GAG interaction could be potentially amplified by TACI’s binding to APRIL. RS-REMD outperformed Autodock3, the docking program previously proven the best for short GAGs.

Inflammatory Cells in Diffuse Large B Cell Lymphoma

Diffuse large B cell lymphoma (DLBCL), known as the most common non-Hodgkin lymphoma (NHL) subtype, is characterized by high clinical and biological heterogeneity. The tumor microenvironment (TME), in which the tumor cells reside, is crucial in the regulation of tumor initiation, progression, and metastasis, but it also has profound effects on therapeutic efficacy. The role of immune cells during DLBCL development is complex and involves reciprocal interactions between tumor cells, adaptive and innate immune cells, their soluble mediators and structural components present in the tumor microenvironment. Different immune cells are recruited into the tumor microenvironment and exert distinct effects on tumor progression and therapeutic outcomes. In this review, we focused on the role of macrophages, Neutrophils, T cells, natural killer cells and dendritic cells in the DLBCL microenvironment and their implication as target for DLBCL treatment. These new therapies, carried out by the induction of adaptive immunity through vaccination or passive of immunologic effectors delivery, enhance the ability of the immune system to react against the tumor antigens inducing the destruction of tumor cells.

The activation of BAFF/APRIL system in spleen and lymph nodes of Plasmodium falciparum infected patients

Previous studies have reported activation of the B cell-activating factor (BAFF)/a proliferation-inducing ligand (APRIL) system in T independent immunity against malaria infection. Plasmodium falciparum (P. falciparum) infected animal model is not feasible. Therefore, little is known about the occurrence of BAFF/APRIL system and changes in falciparum lymphoid tissues. This study aimed to investigate the expression of BAFF/APRIL system components in lymphoid tissues from P. falciparum infected patients. Spleen and lymph node samples from 14 patients were collected at autopsy. Normal spleens and bacterially infected tonsils served as controls. The protein and/or mRNA expression of BAFF/APRIL and their cognate receptors, BAFF-R, TACI and BCMA, were determined by immunohistochemistry and RT-qPCR, respectively. The spleens of the patients exhibited significantly higher BAFF-R protein expression than normal spleens. Although without appropriate control, BCMA protein was markedly observed only in the lymph nodes. BAFF and BCMA mRNA levels were also significantly elevated in the spleen tissues of the patients compared with normal spleens. The overall BAFF-R protein levels in the lymphoid tissues of the patients correlated positively with parasitaemia. These findings are the first to confirm that BAFF/APRIL system activation in lymphoid tissues and is positively correlated with the parasitaemia levels in falciparum malaria.

Novel Insights of Lymphomagenesis of Helicobacter pylori-Dependent Gastric Mucosa-Associated Lymphoid Tissue Lymphoma

Gastric mucosa-associated lymphoid tissue (MALT) lymphoma is the most common subtype of gastric lymphoma. Most gastric MALT lymphomas are characterized by their association with the Helicobacter pylori (HP) infection and are cured by first-line HP eradication therapy (HPE). Several studies have been conducted to investigate why most gastric MALT lymphomas remain localized, are dependent on HP infection, and show HP-specific intratumoral T-cells (e.g., CD40-mediated signaling, T-helper-2 (Th2)-type cytokines, chemokines, costimulatory molecules, and FOXP3+ regulatory T-cells) and their communication with B-cells. Furthermore, the reason why the antigen stimuli of these intratumoral T-cells with tonic B-cell receptor signaling promote lymphomagenesis of gastric MALT lymphoma has also been investigated. In addition to the aforementioned mechanisms, it has been demonstrated that the translocated HP cytotoxin-associated gene A (CagA) can promote B-cell proliferation through the activation of Src homology-2 domain-containing phosphatase (SHP-2) phosphorylation-dependent signaling, extracellular-signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (MAPK), B-cell lymphoma (Bcl)-2, and Bcl-xL. Furthermore, the expression of CagA and these CagA-signaling molecules is closely associated with the HP-dependence of gastric MALT lymphomas (completely respond to first-line HPE). In this article, we summarize evidence of the classical theory of HP-reactive T-cells and the new paradigm of direct interaction between HP and B-cells that contributes to the HP-dependent lymphomagenesis of gastric MALT lymphomas. Although the role of first-line HPE in the treatment of HP-negative gastric MALT lymphoma remains uncertain, several case series suggest that a proportion of HP-negative gastric MALT lymphomas remains antibiotic-responsive and is cured by HPE. Considering the complicated interaction between microbiomes and the genome/epigenome, further studies on the precise mechanisms of HP- and other bacteria-directed lymphomagenesis in antibiotic-responsive gastric MALT lymphomas are warranted.

APRIL is Involved in the Proliferation and Metastasis of Acute Lymphoblastic Leukemia Cells

Our previous work showed that a proliferation-inducing ligand (APRIL) was involved in the development of acute lymphoblastic leukemia (ALL) in children. However, the precise role of APRIL in ALL remains unknown. To investigate this issue, we silenced and overexpressed APRIL in Nalm-6 ALL cells using short hairpin RNA targeting the APRIL gene and recombinant human APRIL, respectively, and evaluated the effects on cell proliferation, apoptosis, and migration. APRIL mRNA and APRIL and matrix metalloproteinase-2 protein levels were evaluated by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and western blott, respectively. We found that APRIL expression was reduced by shRNA-mediated knockdown in Nalm-6 cells; this was associated with a decrease in cell proliferation (P<0.05). APRIL knockdown increased apoptosis (P<0.01) but suppressed cell migration along with matrix metalloproteinase-2 protein level. Overexpressing recombinant human APRIL had the opposite effects in each case (P<0.05). These results demonstrate a link between APRIL expression and ALL development and suggest that APRIL is a potential therapeutic target for ALL treatment.

The role of the BAFF/APRIL system in the T cell-independent specific response to blood stage Plasmodium falciparum hemozoin

BACKGROUND

The B cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) are tumor necrosis factor family members that regulate B cell maturation, proliferation, survival and function. We have previously shown that blood-stage Plasmodium falciparum hemozoin (HZ) can act as a T-independent antigen (TI Ag) that induces the production of specific IgG to soluble crude P. falciparum Ag through the BAFF pathway. However, we have not yet clarified whether HZ need APRIL signaling in the TI response. Here, we aimed to clarify whether both BAFF and APRIL signaling pathways play roles in HZ induction of specific antibody production without T-cell help.

METHODS

Normal monocytes alone or co-cultured with naïve B cells were stimulated by HZ (10 µM) in vitro. Naïve B cell cultures, with HZ alone or with exogenous recombinant BAFF (rBAFF) and recombinant APRIL (rAPRIL) plus recombinant IL-4 (rIL-4) for 6 and 10 days were used as controls to investigate activation of B cells. At various times, the levels of sBAFF, sAPRIL, and HZ-specific IgG in the culture supernatants were assessed by enzyme-linked immunosorbent assay. The BAFF and APRIL expression levels on the HZ-stimulated monocytes and their specific receptors on activated B cells, including the BAFF receptor (BAFF-R), the transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI) and the B cell maturation antigen (BCMA), were determined by flow cytometry. mRNA expression levels for the receptors were validated using Real-Time quantitative PCR.

RESULTS

HZ-activated monocytes released sBAFF and sAPRIL during the 72 h stimulation period. Increased mRNA encoding of their cognate receptors, BAFF-R, TACI, and BCMA, and increased HZ-specific IgG levels were also observed in HZ induction within the monocyte and B cell co-culture. The experiments under control conditions revealed that HZ alone could induce B cell culture to produce a small amount of the specific IgG compared with those in medium alone or rBAFF + rAPRIL + rIL-4.

CONCLUSION

Taken together, we suggest that in the TI response HZ stimulates monocyte and B cell co-culture to produce specific IgG through BAFF, APRIL and other independent complimentary signaling pathways.

CXCL-8/IL8 Produced by Diffuse Large B-cell Lymphomas Recruits Neutrophils Expressing a Proliferation-Inducing Ligand APRIL

Tumor-infiltrating neutrophils have been implicated in malignant development and progression, but mechanisms are ill defined. Neutrophils produce a proliferation-inducing ligand APRIL/TNFSF13, a factor that promotes development of tumors from diverse origins, including diffuse large B-cell lymphoma (DLBCL). High APRIL expression in DLBCL correlates with reduced patient survival, but the pathway(s) dictating APRIL expression are not known. Here, we show that all blood neutrophils constitutively secrete APRIL, and inflammation-associated stimuli, such as TNF, further upregulate APRIL. In a significant fraction of DLBCL patients, tumor cells constitutively produced the ELC-CXC chemokine CXCL-8 (IL8), enabling them to recruit APRIL-producing blood neutrophils. CXCL-8 production in DLBCL was unrelated to the cell of origin, as APRIL-producing neutrophils infiltrated CXCL-8⁺ DLBCL from both germinal center (GC) and non-GC subtypes. Rather, CXCL-8 production implied events affecting DNA methylation and acetylation. Overall, our results showed that chemokine-mediated recruitment of neutrophils secreting the tumor-promoting factor APRIL mediates DLBCL progression. Cancer Res; 77(5); 1097-107. ©2016 AACR.

A proliferation inducing ligand (APRIL) promotes IL-10 production and regulatory functions of human B cells

B cells may have a negative regulatory role, mainly mediated by interleukin 10 (IL-10). We recently showed that regulatory B-cell functions are impaired in patients with rheumatoid arthritis (RA) and that mice transgenic for a proliferation-inducing ligand (APRIL) are protected against collagen-induced arthritis. We aimed to explore the effect of APRIL on human B-cell IL-10 production, in healthy subjects and in patients with RA. The IL-10 production of B-cell was greater with APRIL than with BLyS or control medium, in a dose dependent manner. TACI expression was greater in IL-10 producing B cells (B10) than non-IL-10-producing B cells whereas BAFF-R expression was lower. TNF-α and IFN-γ secretion of T-cells were decreased by APRIL-stimulated B cells. APRIL stimulated STAT3 and STAT3 inhibition decreased B10 cells. APRIL also promoted B10 cells in RA patients. In conclusion, APRIL but not BLyS promotes IL-10 production by CpG-activated B cells and enhances the regulatory role of B cells on T cells. B10 cells in RA patients are responsive to APRIL, which suggests a possible therapeutic application of APRIL to expand B10 cells. This could also explain the difference of clinical efficacy observed between belimumab and atacicept in RA.

The TNF family member APRIL dampens collagen-induced arthritis

BACKGROUND

The tumour necrosis factor (TNF)-family members B cell activating factor (BAFF) and A PRoliferation-Inducing Ligand (APRIL) play important roles in B cell biology, and share binding to B cell maturation antigen and transmembrane activator and cyclophilin ligand interactor, both receptors of the TNF-family. However, while it is reported that BAFF can break B cell tolerance, the role of APRIL in autoimmunity remains elusive.

OBJECTIVE

To evaluate the role of APRIL on collagen-induced arthritis (CIA).

METHODS

CIA was induced in APRIL-transgenic (Tg) DBA/1 mice and littermates. Disease progression was evaluated by clinical and histological signs of arthritis. In another experimental setting mice were exposed to the collagen antibody-induced arthritis. In addition, we tested T cell dependent humoral responses in APRIL-Tg mice.

RESULTS

We found that APRIL-Tg displayed a strongly reduced incidence and severity of CIA compared with littermates, with decreases in collagen-specific autoantibody titres, immune complex deposition and downstream mast cell activation in joints. Notably, ectopic APRIL-expression was also found to negatively regulate T cell dependent humoral responses. The lower autoantibody production in APRIL-Tg mice during CIA appears to be crucial, as arthritis induced by administration of anti-collagen antibodies developed similar in APRIL-Tg and control mice, thus demonstrating that the downstream effector pathways induced by anti-collagen antibodies remain intact in APRIL-Tg mice. This protective effect was specifically mediated by APRIL, as adenoviral delivery of APRIL decreased CIA in a therapeutic setting.

CONCLUSIONS

Collectively, our data identify APRIL as a negative regulator of CIA by regulating autoantibody production. These findings are of important clinical relevance, as the therapeutic potential of transmembrane activator and cyclophilin ligand interactor-Fc (atacicept) is presently evaluated in clinical trials.

Thyroid autoantibodies in pregnancy: their role, regulation and clinical relevance

Autoantibodies to thyroglobulin and thyroid peroxidase are common in the euthyroid population and are considered secondary responses and indicative of thyroid inflammation. By contrast, autoantibodies to the TSH receptor are unique to patients with Graves' disease and to some patients with Hashimoto's thyroiditis. Both types of thyroid antibodies are useful clinical markers of autoimmune thyroid disease and are profoundly influenced by the immune suppression of pregnancy and the resulting loss of such suppression in the postpartum period. Here, we review these three types of thyroid antibodies and their antigens and how they relate to pregnancy itself, obstetric and neonatal outcomes, and the postpartum.

Serum concentrations of A Proliferation-Inducing Ligand (APRIL) are elevated in sepsis and predict mortality in critically ill patients

INTRODUCTION

Inflammatory and autoimmune diseases have been associated with the tumor necrosis factor superfamily member "A PRoliferation Inducing Ligand" (APRIL). However, up to now, APRIL has not been investigated in critical illness or sepsis. We therefore analyzed APRIL serum concentrations in a large cohort of well-characterized intensive care unit patients.

METHODS

Serum concentrations of APRIL were measured in 246 critically ill patients, of which 157 fulfilled sepsis criteria in comparison with 81 healthy controls. Clinical data were recorded and correlated with APRIL serum levels.

RESULTS

We detected strongly elevated serum levels of APRIL in critically ill patients compared with healthy controls. Levels of APRIL were further elevated in sepsis and significantly correlated with classical markers of inflammation, bacterial infection, or multiorgan failure. Consequently, high APRIL levels were associated with an unfavorable prognosis and predicted mortality with higher diagnostic accuracy than established prognostic scoring systems such as the Acute Physiology and Chronic Health Evaluation II score.

CONCLUSION

Serum levels of APRIL were significantly elevated in intensive care unit patients, with the highest concentrations in septic patients, and associated with unfavorable outcome. Besides being used as a single marker, APRIL may be implemented into established scoring systems to further improve their sensitivity and specificity in predicting patient's prognosis.

The design and characterization of receptor-selective APRIL variants

A proliferation-inducing ligand (APRIL), a member of the TNF ligand superfamily with an important role in humoral immunity, is also implicated in several cancers as a prosurvival factor. APRIL binds two different TNF receptors, B cell maturation antigen (BCMA) and transmembrane activator and cylclophilin ligand interactor (TACI), and also interacts independently with heparan sulfate proteoglycans. Because APRIL shares binding of the TNF receptors with B cell activation factor, separating the precise signaling pathways activated by either ligand in a given context has proven quite difficult. In this study, we have used the protein design algorithm FoldX to successfully generate a BCMA-specific variant of APRIL, APRIL-R206E, and two TACI-selective variants, D132F and D132Y. These APRIL variants show selective activity toward their receptors in several in vitro assays. Moreover, we have used these ligands to show that BCMA and TACI have a distinct role in APRIL-induced B cell stimulation. We conclude that these ligands are useful tools for studying APRIL biology in the context of individual receptor activation.

The TNF family member APRIL promotes colorectal tumorigenesis

The tumor necrosis factor (TNF) family member APRIL (A proliferation inducing ligand) is a disease promoter in B-cell malignancies. APRIL has also been associated with a wide range of solid malignancies, including colorectal cancer (CRC). As evidence for a supportive role of APRIL in solid tumor formation was still lacking, we studied the involvement of APRIL in CRC. We observed that ectopic APRIL expression exacerbates the number and size of adenomas in Apc(Min) mice and in a mouse model for colitis-associated colon carcinogenesis. Furthermore, knockdown of APRIL in primary spheroid cultures of colon cancer cells and both mouse and human CRC cell lines reduced tumor clonogenicity and in vivo outgrowth. Taken together, our data therefore indicate that both tumor-derived APRIL and APRIL produced by non-tumor cells is supportive in colorectal tumorigenesis.

Development and characterization of APRIL antagonistic monoclonal antibodies for treatment of B-cell lymphomas

APRIL (A proliferation-inducing ligand) is a TNF family member that binds two TNF receptor family members, TACI and BCMA. It shares these receptors with the closely related TNF family member, B-cell activating factor (BAFF). Contrary to BAFF, APRIL binds heparan sulfate proteoglycans (HSPGs), which regulates cross-linking of APRIL and efficient signaling. APRIL was originally identified as a growth promoter of solid tumors, and more recent evidence defines APRIL also as an important survival factor in several human B-cell malignancies, such as chronic lymphocytic leukemia (CLL). To target APRIL therapeutically, we developed two anti-human APRIL antibodies (hAPRIL.01A and hAPRIL.03A) that block APRIL binding to BCMA and TACI. Their antagonistic properties are unique when compared with a series of commercially available monoclonal anti-human APRIL antibodies as they prevent in vitro proliferation and IgA production of APRIL-reactive B cells. In addition, they effectively impair the CLL-like phenotype of aging APRIL transgenic mice and, more importantly, block APRIL binding to human B-cell lymphomas and prevent the survival effect induced by APRIL. We therefore conclude that these antibodies have potential for further development as therapeutics to target APRIL-dependent survival in B-cell malignancies.

Intrarenal production of B-cell survival factors in human lupus nephritis

The B-cell survival factors APRIL and BLyS are important for B-cell maturation and activation and contribute to human autoimmune diseases. Interference with B-cell function by targeting these molecules is currently being investigated in large clinical trials for systemic lupus erythematosus. The local expression patterns of APRIL and BLyS have not been investigated in detail in kidneys with lupus nephritis. We studied the mRNA expression of APRIL, BLyS, and the corresponding receptors BCMA, TACI, and BAFF-R in microdissected human biopsies with proliferative lupus nephritis (n=25) and compared it with pretransplant biopsies of living donors (n=9). APRIL and BLyS mRNA levels were significantly higher in glomeruli of patients with proliferative lupus nephritis (12- and 30-fold, respectively). Tubulointerstitial expression of APRIL, BLyS, BCMA, and TACI was also significantly elevated. To localize the respective proteins in the kidney, APRIL, BLyS, and BAFF-R were studied by immunohistochemistry in renal biopsies with proliferative (n=21) or membranous (n=8) lupus nephritis. APRIL was prominently expressed in glomeruli with proliferative, but not membranous, lupus nephritis. The staining pattern was consistent with mesangial cells. A prominent accumulation of CD68-positive cells was present in glomeruli in association with APRIL expression. APRIL, BLyS, and BAFF-R were also expressed in interstitial inflammatory cell accumulation. This is the first study, which details local expression of APRIL and BLyS in glomeruli and tubulointerstitium of human proliferative lupus nephritis. This information might help define intrarenal effects of APRIL and BLyS inhibition in human lupus nephritis.

Factors supporting intrathecal humoral responses following viral encephalomyelitis

Central nervous system (CNS) infections and autoimmune inflammatory disorders are often associated with retention of antibody-secreting cells (ASC). Although beneficial or detrimental contributions of ASC to CNS diseases remain to be defined, virus-specific ASC are crucial in controlling persistent CNS infection following coronavirus-induced encephalomyelitis. This report characterizes expression kinetics of factors associated with ASC homing, differentiation, and survival in the spinal cord, the prominent site of coronavirus persistence. Infection induced a vast, gamma interferon (IFN-γ)-dependent, prolonged increase in chemokine (C-X-C motif) ligand 9 (CXCL9), CXCL10, and CXCL11 mRNA, supporting a role for chemokine (C-X-C motif) receptor 3 (CXCR3)-mediated ASC recruitment. Similarly, CD4 T cell-secreted interleukin-21, a critical regulator of both peripheral activated B cells and CD8 T cells, was sustained during viral persistence. The ASC survival factors B cell-activating factor of the tumor necrosis factor (TNF) family (BAFF) and a proliferating-inducing ligand (APRIL) were also significantly elevated in the infected CNS, albeit delayed relative to the chemokines. Unlike IFN-γ-dependent BAFF upregulation, APRIL induction was IFN-γ independent. Moreover, both APRIL and BAFF were predominantly localized to astrocytes. Last, the expression kinetics of the APRIL and BAFF receptors coincided with CNS accumulation of ASC. Therefore, the factors associated with ASC migration, differentiation, and survival are all induced during acute viral encephalomyelitis, prior to ASC accumulation in the CNS. Importantly, the CNS expression kinetics implicate rapid establishment, and subsequent maintenance, of an environment capable of supporting differentiation and survival of protective antiviral ASC, recruited as plasmablasts from lymphoid organs.

The TNF superfamily in 2009: new pathways, new indications, and new drugs

Today's most successful class of biologics targets the inflammatory cytokine tumor necrosis factor in autoimmune diseases including rheumatoid arthritis, psoriasis and Crohn's. With five anti-TNF biologics now on the market, attention has turned toward novel strategies to improve the safety and efficacy of next-generation TNF inhibitors. Beyond TNF, drugs are under development that modulate many other ligands and receptors of the TNF superfamily. Biologics targeting at least 16 of the approximately 22 known ligand-receptor pairs are now in clinical development for autoimmune diseases, cancers and osteoporosis. A deeper understanding of intracellular signaling has also facilitated small-molecule interventions, opening the door to oral therapies. This report summarizes recent developments in this highly druggable superfamily, including highlights of the latest international TNF conference.