Regulatory effects of novel neurotrophin-1/b cell-stimulating factor-3 (cardiotrophin-like cytokine) on B cell function

Detection of CLCF1 protein expression by flow cytometry

Cardiotrophin-like cytokine factor 1 (CLCF1) is an IL-6 family cytokine with neurotrophic and immuno-modulating functions. CLCF1 mRNA has been detected in primary and secondary lymphoid organs, and up-regulation of CLCF1 mRNA levels has been associated with the T helper (Th) 17 polarization. However, information regarding CLCF1 expression by immune cells at the protein level remains scarce. We have developed a methodology that uses a monoclonal antibody (mAb) directed against CLCF1 for the detection of human and mouse CLCF1 by flow cytometry. We have successfully detected CLCF1 protein expression in cells from the mouse pro-B cell line Ba/F3 that were transduced with CLCF1 cDNA. Interestingly, we found that the anti-CLCF1 mAb inhibits CLCF1 biological activity in vitro by binding to an epitope that encompasses site III of the cytokine. Moreover, we have detected CLCF1 expression in mouse splenic T cells, as well as in vitro differentiated Th1 cells. The specificity of the fluorescence signal was demonstrated using Clcf1-deficient lymphocytes generated using a conditional knock-out mouse model. The detection of CLCF1 protein by flow cytometry will be a valuable tool to study CLCF1 expression during normal and pathological immune responses.

Transcription factor abnormalities in B-ALL leukemogenesis and treatment

The biological regulation of transcription factors (TFs) and repressor proteins is an important mechanism for maintaining cell homeostasis. In B cell acute lymphoblastic leukemia (B-ALL) TF abnormalities occur at high frequency and are often recognized as the major driving factor in carcinogenesis. We provide an in-depth review of molecular mechanisms of six major TF rearrangements in B-ALL, including DUX4-rearranged (DUX4-R), MEF2D-R, ZNF384-R, ETV6-RUNX1 and TCF3-PBX1 fusions, and KMT2A-R. In addition, the therapeutic options and prognoses for patients who harbor these TF abnormalities are discussed. This review aims to provide an up-to-date panoramic view of how TF-based oncogenic fusions might drive carcinogenesis and impact on potential therapeutic exploration of B-ALL treatments.

Current understanding of the molecular mechanisms of circulating permeability factor in focal segmental glomerulosclerosis

The pathogenetic mechanisms underlying the onset and the post-transplant recurrence of primary focal segmental glomerulosclerosis (FSGS) are complex and remain yet to be fully elucidated. However, a growing body of evidence emphasizes the pivotal role of the immune system in both initiating and perpetuating the disease. Extensive investigations, encompassing both experimental models and patient studies, have implicated T cells, B cells, and complement as crucial actors in the pathogenesis of primary FSGS, with various molecules being proposed as potential "circulating factors" contributing to the disease and its recurrence post kidney-transplantation. In this review, we critically assessed the existing literature to identify essential pathways for a comprehensive characterization of the pathogenesis of FSGS. Recent discoveries have shed further light on the intricate interplay between these mechanisms. We present an overview of the current understanding of the engagement of distinct molecules and immune cells in FSGS pathogenesis while highlighting critical knowledge gaps that require attention. A thorough characterization of these intricate immune mechanisms holds the potential to identify noninvasive biomarkers that can accurately identify patients at high risk of post-transplant recurrence. Such knowledge can pave the way for the development of targeted and personalized therapeutic approaches in the management of FSGS.

CRLF1 and CLCF1 in Development, Health and Disease

Cytokines and their receptors have a vital function in regulating various processes such as immune function, inflammation, haematopoiesis, cell growth and differentiation. The interaction between a cytokine and its specific receptor triggers intracellular signalling cascades that lead to altered gene expression in the target cell and consequent changes in its proliferation, differentiation, or activation. In this review, we highlight the role of the soluble type I cytokine receptor CRLF1 (cytokine receptor-like factor-1) and the Interleukin (IL)-6 cytokine CLCF1 (cardiotrophin-like cytokine factor 1) during development in physiological and pathological conditions with particular emphasis on Crisponi/cold-induced sweating syndrome (CS/CISS) and discuss new insights, challenges and possibilities arising from recent studies.

Cardiotrophin Like Cytokine Factor 1 (CLCF1) alleviates bone loss in osteoporosis mouse models by suppressing osteoclast differentiation through activating interferon signaling and repressing the nuclear factor-κB signaling pathway

A growing body of evidence suggests that immune factors that regulate osteoclast differentiation and bone resorption might be promising therapeutic agents for the treatment of osteoporosis. The expression of CLCF1, an immune cell-derived molecule, has been reported to be reduced in patients with postmenopausal osteoporosis. This suggests that it may be involved in bone remodeling. Thus, we explored the functional role of CLCF1 in osteoclastogenesis and bone loss associated with osteoporosis. Surprisingly, the administration of recombinant CLCF1 repressed excessive bone loss in ovariectomized mice and prevented RANKL-induced bone loss in calvarial mouse model. Likewise, the addition of recombinant CLCF1 to RANKL-stimulated monocytes resulted in a significant suppression in the number of differentiated osteoclasts with small resorption areas being observed on dentine slices in vitro. At the same dosage, CLCF1 did not exhibit any detectable negative effects on the differentiation of osteoblasts. Mechanistically, the inhibition of osteoclast differentiation by the CLCF1 treatment appears to be related to the activation of interferon signaling (IFN) and the suppression of the NF-κB signaling pathway. Interestingly, the expression of the main components of IFN-signaling namely, STAT1 and IRF1, was detected in macrophages as early as 1 h after stimulation with CLCF1. Consistent with these results, the blockade of STAT1 in macrophages abolished the inhibitory effect of CLCF1 on osteoclast differentiation in vitro. These collective findings point to a novel immunoregulatory function of CLCF1 in bone remodeling and highlight it as a potentially useful therapeutic agent for the treatment of osteoporosis.

A comparative analysis of the intrauterine transcriptome in fertile and subfertile mares using cytobrush sampling

Background

Subfertility is a major problem in modern horse breeding. Especially, mares without clinical signs of reproductive diseases, without known uterine pathogens and no evidence of inflammation but not becoming pregnant after several breeding attempts are challenging for veterinarians. To obtain new insights into the cause of these fertility problems and aiming at improving diagnosis of subfertile mares, a comparative analysis of the intrauterine transcriptome in subfertile and fertile mares was performed. Uterine cytobrush samples were collected during estrus from 57 mares without clinical signs of uterine diseases. RNA was extracted from the cytobrush samples and samples from 11 selected subfertile and 11 fertile mares were used for Illumina RNA-sequencing.

Results

The cytobrush sampling was a suitable technique to isolate enough RNA of high quality for transcriptome analysis. Comparing subfertile and fertile mares, 114 differentially expressed genes (FDR = 10%) were identified. Metascape enrichment analysis revealed that genes with lower mRNA levels in subfertile mares were related to ‘extracellular matrix (ECM)’, ‘ECM-receptor interaction’, ‘focal adhesion’, ‘immune response’ and ‘cytosolic calcium ion concentration’, while DEGs with higher levels in subfertile mares were enriched for ‘monocarboxyl acid transmembrane transport activity’ and ‘protein targeting’.

Conclusion

Our study revealed significant differences in the uterine transcriptome between fertile and subfertile mares and provides leads for potential uterine molecular biomarkers of subfertility in the mare.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07701-3.

Assessing the Multivariate Relationship between the Human Infant Intestinal Exfoliated Cell Transcriptome (Exfoliome) and Microbiome in Response to Diet

Gut microbiota and the host exist in a mutualistic relationship, with the functional composition of the microbiota strongly influencing the health and well-being of the host. In addition to the standard differential expression analysis of host genes to assess the complex cross-talk between environment (diet), microbiome, and host intestinal physiology, data-driven integrative approaches are needed to identify potential biomarkers of both host genes and microbial communities that characterize these interactions. Our findings demonstrate that the complementary application of univariate differential gene expression analysis and multivariate approaches such as sparse Canonical Correlation Analysis (sCCA) and sparse Principal Components Analysis (sPCA) can be used to integrate data from both the healthy infant gut microbial community and host transcriptome (exfoliome) using stool derived exfoliated cells shed from the gut. These approaches reveal host genes and microbial functional categories related to the feeding phenotype of the infants. Our findings also confirm that combinatorial noninvasive -omic approaches provide an integrative genomics-based perspective of neonatal host-gut microbiome interactions.

Cardiotrophin-Like Cytokine Factor 1 Exhibits a Myeloid-Biased Hematopoietic-Stimulating Function

Cardiotrophin-like cytokine factor 1 (CLCF1) is secreted as a complex with the cytokine receptor-like factor 1 (CRLF1). Syndromes caused by mutations in the genes encoding CLCF1 or CRLF1 suggest an important role for CLCF1 in the development and regulation of the immune system. In mice, CLCF1 induces B-cell expansion, enhances humoral responses and triggers autoimmunity. Interestingly, inactivation of CRLF1, which impedes CLCF1 secretion, leads to a marked reduction in the number of bone marrow (BM) progenitor cells, while mice heterozygous for CLCF1 display a significant decrease in their circulating leukocytes. We therefore hypothesized that CLCF1 might be implicated in the regulation of hematopoiesis. To test this hypothesis, murine hematopoietic progenitor cells defined as Lin⁻Sca1⁺c-kit⁺ (LSK) were treated in vitro with ascending doses of CLCF1. The frequency and counts of LSK cells were significantly increased in the presence of CLCF1, which may be mediated by several CLCF1-induced soluble factors including IL-6, G-CSF, IL-1β, IL-10, and VEGF. CLCF1 administration to non-diseased C57BL/6 mice resulted in a pronounced increase in circulating myeloid cells, which was concomitant with augmented LSK and myeloid cell counts in the BM. Likewise, CLCF1 administration to mice following sub-lethal irradiation or congeneic BM transplantation (BMT) resulted in accelerated LSK recovery along with a sustained increase in BM-derived CD11b⁺ cells. Altogether, our observations establish an important and unforeseen role for CLCF1 in regulating hematopoiesis with a bias toward myeloid cell differentiation.

Analyses of miRNA in the ileum of diarrheic piglets caused by Clostridium perfringens type C

Clostridium perfringens (C. perfringens) type C is one of major pathogenic causing diarrhea and other intestinal inflammatory diseases in piglets, which seriously affects the healthy development of the swine industries. Studies have found that miRNAs play important roles in regulating piglet diarrhea challenged by pathogenic E. coli and Salmonella. However, little is known miRNAs in the ileum of diarrheic piglets caused by C. perfringens type C. Therefore, we studied the expression profiles of the ileum miRNAs of 7-day-old piglets infected with C. perfringens type C using small RNA-Seq, including control (IC), susceptible (IS) and resistant (IR) groups. As a result, 53 differentially expressed miRNAs were found. KEGG pathway analysis for target genes revealed that these miRNAs were involved in ErbB signaling pathway, MAPK signaling pathway, Jak-STAT signaling pathway and Wnt signaling pathway. The expression correlation analysis between miRNAs and target genes revealed that the expression of miR-7134-5p had negative correlation with target NFATC4, miR-500 had negative correlation with target ELK1, HSPA2 and IL7R, and miR-92b-3p had negative correlation with target CLCF1 in ileum of IR vs IS group, suggesting that miR-7134-5p targeting to NFATC4, miR-500 targeting to ELK1, HSPA2 and IL7R, and miR-92b-3p targeting to CLCF1 were probably involved in piglet resisting C. perfringens type C. The results will provide value resources for better understanding of the genetic basis of C. perfringens type C resistance in piglet and lays a new foundation for identifying novel markers of C. perfringens type C resistance.

Cardiotrophin-like cytokine (CLCF1) modulates mesenchymal stem cell osteoblastic differentiation

Mesenchymal stem cells (MSCs) are multipotent cells capable of differentiating into adipocytes, chondrocytes, or osteocytes. MSCs secrete an array of cytokines and express the LIFRβ (leukemia inhibitory factor receptor) chain on their surface. Mutations in the gene coding for LIFRβ lead to a syndrome with altered bone metabolism. LIFRβ is one of the signaling receptor chains for cardiotrophin-like cytokine (CLCF1), a neurotrophic factor known to modulate B and myeloid cell functions. We investigated its effect on MSCs induced to differentiate into osteocytes in vitro Our results indicate that CLCF1 binds mouse MSCs, triggers STAT1 and -3 phosphorylation, inhibits the up-regulation of master genes involved in the control of osteogenesis, and markedly prevents osteoblast generation and mineralization. This suggests that CLCF1 could be a target for therapeutic intervention with agents such as cytokine traps or blocking mAbs in bone diseases such as osteoporosis.

Genetics of Childhood Steroid Sensitive Nephrotic Syndrome: An Update

Advances in genome science in the last 20 years have led to the discovery of over 50 single gene causes and genetic risk loci for steroid resistant nephrotic syndrome (SRNS). Despite these advances, the genetic architecture of childhood steroid sensitive nephrotic syndrome (SSNS) remains poorly understood due in large part to the varying clinical course of SSNS over time. Recent exome and genome wide association studies from well-defined cohorts of children with SSNS identified variants in multiple MHC class II molecules such as HLA-DQA1 and HLA-DQB1 as risk factors for SSNS, thus stressing the central role of adaptive immunity in the pathogenesis of SSNS. However, evidence suggests that unknown second hit risk loci outside of the MHC locus and environmental factors also make significant contributions to disease. In this review, we examine what is currently known about the genetics of SSNS, the implications of recent findings on our understanding of pathogenesis of SSNS, and how we can utilize these results and findings from future studies to improve the management of children with nephrotic syndrome.

FcγRIIb on B Cells and Myeloid Cells Modulates B Cell Activation and Autoantibody Responses via Different but Synergistic Pathways in Lupus-Prone Yaa Mice

C57BL/6 (B6).FcγRIIb^-/- Yaa mice spontaneously develop lethal lupus nephritis. To define the cell type-specific role of FcγRIIb in Yaa-associated lupus, we established B cell- (CD19^Cre Yaa), myeloid cell- (C/EBPα^Cre Yaa), and dendritic cell- (DC) (CD11c^Cre Yaa) specific FcγRIIb-deficient B6.Yaa mouse strains. CD19^Cre Yaa mice developed milder lupus than B6.FcγRIIb^-/- Yaa mice, indicating that FcγRIIb deficiency on B cells is not sufficient for the development of severe disease. Surprisingly, C/EBPα^Cre Yaa mice also showed autoantibody production and mild lupus similar to that in CD19^Cre Yaa mice, whereas CD11c^Cre Yaa mice stayed disease free. These observations indicate that FcγRIIb deficiency in B cells and myeloid cells, but not DCs, contributes to the severe disease in B6.FcγRIIb^-/- Yaa mice. Flow cytometric analysis showed that the frequency of peripheral Gr-1^- but not Gr-1⁺ monocyte was increased in B6.FcγRIIb^-/- Yaa and C/EBPα^Cre Yaa but not CD19^Cre Yaa mice, suggesting a link between FcγRIIb deficiency on myeloid cells and the high frequency of Gr-1^- monocytes. RNA sequencing revealed that compared with Gr-1⁺ monocytes, Gr-1^- monocytes expressed higher levels of the B cell-stimulating cytokines BSF-3, IL-10, and IL-1β, the DC markers CD11c, CD83, and Adamdec1, and the antiapoptotic factors Bcl2 and Bcl6. In conclusion, in Yaa-associated lupus nephritis, FcγRIIb on B cells and myeloid cells modulates B cell activation via different but synergistic pathways. Gr-1^- monocytes are the most likely candidate myeloid cells involved.

Anti-CD11b antibody treatment suppresses the osteoclast generation, inflammatory cell infiltration, and autoantibody production in arthritis-prone FcγRIIB-deficient mice

BACKGROUND

Previously we established an arthritis-prone FcγRIIB-deficient mouse strain (designated KO1). Anti-mouse CD11b mAb (5C6) has been reported to inhibit the recruitment of peripheral CD11b⁺ myelomonocytic cells from the blood to the inflammatory site. These cells include neutrophils and monocytes, both of which play important roles in the development of arthritis. Here we treated KO1 mice with 5C6 mAb in order to study its effect on arthritis development.

METHODS

To evaluate the disease-preventive effect of 5C6, 4-month-old preclinical KO1 mice were divided into three groups: the first treated with 5C6 for 6 months, the second treated with normal rat IgG for 6 months, as a control, and the third left untreated. Arthritis severity and immunological abnormalities were compared among the groups, along with transcriptional levels of several important arthritis-related factors in ankle joints, spleen, and peripheral blood cells.

RESULTS

The 5C6 treatment ameliorated arthritis in KO1 mice, showing decreases in inflammatory cell infiltration and osteoclast formation. Analysis of transcriptional levels in ankle joints revealed that compared with the two control groups, the 5C6-treated group showed downregulated expression of RANK, RANKL, MCP-1, RANTES, TNFα, and IL-6, and at the same time showed significantly up-regulated expression of the decoy receptor for RANKL, i.e. osteoprotegerin. In addition, the disease suppression was associated with the lower serum levels of autoantibodies, and the decreased frequencies of activated B cells and plasma cells. The expression levels of B cell activation/differentiation-related cytokines were suppressed in spleen and peripheral leukocytes of the 5C6-treated mice. Intriguingly, while untreated KO1 mice spontaneously developed marked monocytosis, the 5C6-treated mice showed the significantly down-regulated frequency of monocytes.

CONCLUSIONS

The outcome of 5C6 treatment was complex, in which the 5C6-mediated disease-preventive effect is likely due on one hand to the decrease in the recruitment of inflammatory cells and osteoclast precursor monocytes from the periphery into the joints, and on the other hand to the suppression of B cell activation/maturation and of autoantibody production via the suppression of B cell stimulating cytokine production. The lower levels of these cytokines may be the secondary effect of the lower frequency of monocytes, since monocytes/macrophages are the major producers of these cytokines.

Whole-transcriptome sequencing identifies a distinct subtype of acute lymphoblastic leukemia with predominant genomic abnormalities of EP300 and CREBBP

Chromosomal translocations are a genomic hallmark of many hematologic malignancies. Often as initiating events, these structural abnormalities result in fusion proteins involving transcription factors important for hematopoietic differentiation and/or signaling molecules regulating cell proliferation and cell cycle. In contrast, epigenetic regulator genes are more frequently targeted by somatic sequence mutations, possibly as secondary events to further potentiate leukemogenesis. Through comprehensive whole-transcriptome sequencing of 231 children with acute lymphoblastic leukemia (ALL), we identified 58 putative functional and predominant fusion genes in 54.1% of patients (n = 125), 31 of which have not been reported previously. In particular, we described a distinct ALL subtype with a characteristic gene expression signature predominantly driven by chromosomal rearrangements of the ZNF384 gene with histone acetyltransferases EP300 and CREBBP. ZNF384-rearranged ALL showed significant up-regulation of CLCF1 and BTLA expression, and ZNF384 fusion proteins consistently showed higher activity to promote transcription of these target genes relative to wild-type ZNF384 in vitro. Ectopic expression of EP300-ZNF384 and CREBBP-ZNF384 fusion altered differentiation of mouse hematopoietic stem and progenitor cells and also potentiated oncogenic transformation in vitro. EP300- and CREBBP-ZNF384 fusions resulted in loss of histone lysine acetyltransferase activity in a dominant-negative fashion, with concomitant global reduction of histone acetylation and increased sensitivity of leukemia cells to histone deacetylase inhibitors. In conclusion, our results indicate that gene fusion is a common class of genomic abnormalities in childhood ALL and that recurrent translocations involving EP300 and CREBBP may cause epigenetic deregulation with potential for therapeutic targeting.

Comparison of Renal Amyloid and Hyaline Glomerulopathy in B6C3F1 Mice: An NTP Retrospective Study

Due to potential misdiagnosis of hyaline glomerulopathy (HG) for amyloidosis, a retrospective study of B6C3F1 mice from the National Toxicology Program (NTP) archives was undertaken to determine whether HG had occurred in prior NTP studies and, if so, whether these 2 glomerular lesions could be routinely discriminated. Kidney slides from 7 amyloid-positive control mice, 2 HG-positive control mice, 3 normal or negative control mice, and 41 potential HG mice (with renal-only deposits previously diagnosed as amyloid) were evaluated using hematoxylin and eosin (H&E), periodic acid Schiff (PAS), Congo red (CR), and Masson's trichrome (MT) stains. Utilizing these techniques, HG was reliably distinguished from amyloidosis. All 41 potential HG mice had glomerular deposits histochemically inconsistent with amyloid; the deposits were PAS positive and CR negative. Four of the 41 mice were selected for transmission electron microscopy of the glomerular deposits; ultrastructurally, the deposits in these animals were consistent with HG and not amyloid. Our findings indicate that HG is a spontaneous lesion in B6C3F1 mice of low occurrence, is commonly misdiagnosed as amyloidosis, and is more likely than amyloid to cause glomerular deposits in mice without evidence of deposits in other tissues. Also, HG can be distinguished from amyloid on H&E evaluation; however, the distinction is improved with use of PAS or CR staining and/or ultraviolet evaluation.

The glomerular permeability factors in idiopathic nephrotic syndrome

It is currently postulated that steroid-sensitive idiopathic nephrotic syndrome (SSNS) and steroid-resistant idiopathic nephrotic syndrome (SRNS), which are not related to the mutation of a gene coding for podocyte structures or for glomerular basement membrane proteins, result from a circulating factor affecting podocyte shape and function. T lymphocytes have for a long time been suspected to be involved in the pathophysiology of these diseases. The successful treatment of steroid-dependant nephrotic syndrome with rituximab suggests a potential role for B lymphocytes. Clinical and experimental data indicate roles for cytokines IL-13, TNFα, circulating cardiotrophin-like cytokine factor 1 (member of the IL-6 family), circulating hemopexin, radical oxygen species, and the soluble urokinase-type plasminogen activator receptor (suPAR) in the development of nephrotic syndrome. Podocyte metabolism modifications-leading to the overexpression of the podocyte B7-1antigen (CD 80), hypoactivity of the podocyte enzyme sphingomyelin phosphodiesterase acid-like 3 b (SMPDL3b), and to the podocyte production of a hyposialylated form of the angiopoietin-like 4 (Angptl4)-are mechanisms possibly involved in the changes in the podocyte cytoskeleton leading to SSNS and or SRNS. Different multifactorial pathophysiological mechanisms can be advocated for SSNS and SRNS. The present paper reviews the experimental and clinical data upon which the different hypotheses are based and reports their possible clinical applications.

[Glomerulopathies with organized monoclonal immunoglobulin deposits]

The spectrum of glomerular disorders with organized immunoglobulin (Ig) deposits is heterogeneous. It encompasses 2 mains categories: glomerulopathies with fibrillary deposits are mostly represented by immunoglobulinic amyloidosis (most commonly AL amyloidosis, characterized by monoclonal light chain deposits often of the lambda isotype), and pseudo-amyloid fibrillary glomerulonephritis in which deposits predominantly contain polyclonal IgG4. Glomerulopathies with microtubular deposits include cryoglobulinemic glomerulonephritis (type I and type II, with or without detectable serum cryoglobulin) and glomerulonephritis with organized microtubular monoclonal Ig deposits (GOMMID) also referred to as immunotactoid glomerulopathy. Pathological diagnosis requires meticulous studies by light microscopy (with systematic Congo red staining), immunofluorescence with specific conjugates, and electron microscopy. Ultrastructural studies are required to differentiate amyloid fibrils (8 to 10 nm in external diameter), pseudo-amyloid fibrils (15-20 nm) and microtubules (10 to 50 nm in external diameter, with a central hollow core). Glomerular deposits in type I cryoglobulinemic glomerulonephritis are arranged into parallel straight microtubules similar to those observed in GOMMID, but with different topography that allows distinction between the two entities. Glomerular substructures composed of circulating Igs should be distinguished from collagen fibrils that are commonly observed in glomerular disorders with or without deposition of monoclonal or polyclonal Igs.

Janus kinase 2/signal transducer and activator of transcription 3 inhibitors attenuate the effect of cardiotrophin-like cytokine factor 1 and human focal segmental glomerulosclerosis serum on glomerular filtration barrier

Recurrence of idiopathic focal segmental glomerulosclerosis (FSGS) after renal transplantation is believed to be caused by a circulating factor(s). We detected cardiotrophin-like cytokine factor 1 (CLCF1), a member of the interleukin 6 family, in the plasma from patients with recurrent FSGS. We hypothesized that CLCF1 contributes to the effect of FSGS serum on the glomerular filtration barrier in vitro. Presently, we studied the effect of CLCF1 on isolated rat glomeruli using an in vitro assay of albumin permeability (P(alb)). CLCF1 (0.05-100 ng/mL) increased P(alb) and caused maximal effect at 5-10 ng/mL (P < 0.001). The increase in Palb was analogous to the effect of FSGS serum. Anti-CLCF1 monoclonal antibody blocked the CLCF1-induced increase in P(alb) and significantly attenuated the effect of FSGS serum (P < 0.001). The heterodimer composed of CLCF1 and cosecreted molecule cytokine receptor-like factor 1 (CRLF1) attenuated the increase in P(alb) caused by CLCF1 or FSGS serum. Western blot analysis showed that CLCF1 upregulated phosphorylation of signal transducer and activator of transcription 3 (STAT3) (Tyr705) in glomeruli. This effect was diminished by the heterodimer CLCF1-CRLF1. Janus kinase 2 (JAK2) inhibitor BMS-1119543 or STAT3 inhibitor Stattic significantly blocked the effect of CLCF1 or FSGS serum on P(alb) (P < 0.001). These novel findings suggest that when monomeric CLCF1 increases P(alb), the heterodimer CLCF1-CRLF1 may protect the glomerular filtration barrier. We speculate that albuminuria in FSGS is related to qualitative or quantitative changes in the CLCF1-CRLF1 complex, and that JAK2 or STAT3 inhibitors may be novel therapeutic agents to treat FSGS.

Renal and Hematological Effects of CLCF-1, a B-Cell-Stimulating Cytokine of the IL-6 Family

CLCF-1 is a cytokine known for B-cell stimulation and for neurotrophic properties. We have identified CLCF-1 as a potential injurious factor in the human renal disease focal segmental glomerulosclerosis (FSGS). We investigated its effects on renal cells and renal function in in vitro and in vivo studies. Methods include measurement of the effect of CLCF-1 on phosphorylation of target molecules of the JAK/STAT pathway, on cytoskeleton and cell morphology in cultured podocytes, on albumin permeability of isolated rat glomeruli, and on tissue phosphorylation and urine albumin after acute or chronic CLCF-1 injection. In addition, cell sorting was performed to determine the presence of cells expressing CLCF-1 in spleen and bone marrow of normal mice and the effect of CLCF-1 infusion on splenic B-cell populations. CLCF-1 increased phosphorylation of STAT3 in multiple cell types, activated podocytes leading to formation of lamellipodia and decrease in basal stress fibers, increased glomerular albumin permeability, and increased STAT3 phosphorylation of peripheral blood cells and renal cortex. CLCF-1 increased urine albumin/creatinine ratio in mice and increased B-cell expression of IgG in mouse spleen. We conclude that CLCF-1 has potentially important systemic effects, alters podocyte function, and may contribute to renal dysfunction and albuminuria.

Correlation of gene expression and genome mutation in single B-cells

High-throughput measurement of gene-expression and immune receptor repertoires have recently become powerful tools in the study of adaptive immune response. However, despite their now-widespread use, both tend to discard cell identity by treating cell populations in bulk, and therefore lose the correlation between genetic variability and gene-expression at the single cell level. In order to recover this information, we developed a method to simultaneously measure gene expression profiles and genome mutations in single cells. We applied this method by quantifying the relationships between gene expression and antibody mutation in ensembles of individual B-cells from immunized mice. The results reveal correlations reflecting the manner in which information propagates between a B-cell’s antigen receptors, its gene expression, and its mutagenic machinery, and demonstrate the power of this approach to illuminate both heterogeneity and physiology in cell populations.

Focused examination of the intestinal lamina propria yields greater molecular insight into mechanisms underlying SIV induced immune dysfunction

Background

The Gastrointestinal (GI) tract is critical to AIDS pathogenesis as it is the primary site for viral transmission and a major site of viral replication and CD4⁺ T cell destruction. Consequently GI disease, a major complication of HIV/SIV infection can facilitate translocation of lumenal bacterial products causing localized/systemic immune activation leading to AIDS progression.

Methodology/Principal Findings

To better understand the molecular mechanisms underlying GI disease we analyzed global gene expression profiles sequentially in the intestine of the same animals prior to and at 21 and 90d post SIV infection (PI). More importantly we maximized information gathering by examining distinct mucosal components (intraepithelial lymphocytes, lamina propria leukocytes [LPL], epithelium and fibrovascular stroma) separately. The use of sequential intestinal resections combined with focused examination of distinct mucosal compartments represents novel approaches not previously attempted. Here we report data pertaining to the LPL. A significant increase (±1.7-fold) in immune defense/inflammation, cell adhesion/migration, cell signaling, transcription and cell division/differentiation genes were observed at 21 and 90d PI. Genes associated with the JAK-STAT pathway (IL21, IL12R, STAT5A, IL10, SOCS1) and T-cell activation (NFATc1, CDK6, Gelsolin, Moesin) were notably upregulated at 21d PI. Markedly downregulated genes at 21d PI included IL17D/IL27 and IL28B/IFNγ3 (anti-HIV/viral), activation induced cytidine deaminase (B-cell function) and approximately 57 genes regulating oxidative phosphorylation, a critical metabolic shift associated with T-cell activation. The 90d transcriptome revealed further augmentation of inflammation (CXCL11, chitinase-1, JNK3), immune activation (CD38, semaphorin7A, CD109), B-cell dysfunction (CD70), intestinal microbial translocation (Lipopolysaccharide binding protein) and mitochondrial antiviral signaling (NLRX1) genes. Reduced expression of CD28, CD4, CD86, CD93, NFATc1 (T-cells), TLR8, IL8, CCL18, DECTIN1 (macrophages), HLA-DOA and GPR183 (B-cells) at 90d PI suggests further deterioration of overall immune function.

Conclusions/Significance

The reported transcriptional signatures provide significant new details on the molecular pathology of HIV/SIV induced GI disease and provide new opportunity for future investigation.

Hyaline glomerulopathy with tubulo-fibrillary deposits in young ddY mice

Hyaline glomerulopathy with tubulo-fibrillary deposits was observed in two young female ddY mice. One of the mice showed gross systemic edema and bilateral enlargement and pale color of the kidneys, whereas no significant gross findings were noted in the other mouse. Microscopically, a large number of the glomeruli in both mice were enlarged because of diffuse and global deposition of amorphous eosinophilic materials. The deposits were negatively stained with Congo red and positively stained with IgG, IgM, IgA, C3, and periodic acid-Schiff. Electron microscopic examination revealed microtubular and fibrillary deposits with diameters of 80-100 and 9-16 nm, respectively, in the subendothelial space of the glomeruli. These features are histopathologically similar to immunotactoid glomerulopathy or fibrillary glomerulonephritis according to the classification of human glomerular lesions. Understanding of these characteristics of hyaline glomerulopathy in ddY mice is essential when evaluating pharmacological, pharmacokinetic, and toxicological studies using this mouse strain.

Proceedings of the 2010 National Toxicology Program Satellite Symposium

The 2010 annual National Toxicology Program (NTP) Satellite Symposium, entitled "Pathology Potpourri," was held in Chicago, Illinois, in advance of the scientific symposium sponsored jointly by the Society of Toxicologic Pathology (STP) and the International Federation of Societies of Toxicologic Pathologists (IFSTP). The goal of the annual NTP Symposium is to present current diagnostic pathology or nomenclature issues to the toxicologic pathology community. This article presents summaries of the speakers' presentations, including diagnostic or nomenclature issues that were presented, along with select images that were used for voting or discussion. Some topics covered during the symposium included a comparison of rat and mouse hepatocholangiocarcinoma, a comparison of cholangiofibrosis and cholangiocarcinoma in rats, a mixed pancreatic neoplasm with acinar and islet cell components, an unusual preputial gland tumor, renal hyaline glomerulopathy in rats and mice, eosinophilic substance in the nasal septum of mice, INHAND nomenclature for proliferative and nonproliferative lesions of the CNS/PNS, retinal gliosis in a rat, fibroadnexal hamartoma in rats, intramural plaque in a mouse, a treatment-related chloracne-like lesion in mice, and an overview of mouse ovarian tumors.

A role for IL-27p28 as an antagonist of gp130-mediated signaling

The heterodimeric cytokine interleukin 27 (IL-27) signals through the IL-27Rα subunit of its receptor, combined with gp130, a common receptor chain used by several cytokines, including IL-6. Notably, the IL-27 subunits p28 (IL-27p28) and EBI3 are not always expressed together, which suggests that they may have unique functions. Here we show that IL-27p28, independently of EBI3, antagonized cytokine signaling through gp130 and IL-6-mediated production of IL-17 and IL-10. Similarly, the ability to generate antibody responses was dependent on the activity of gp130-signaling cytokines. Mice transgenic for expression of IL-27p28 showed a substantial defect in the formation of germinal centers and antibody production. Thus, IL-27p28, as a natural antagonist of gp130-mediated signaling, may be useful as a therapeutic for managing inflammation mediated by cytokines that signal through gp130.

Elucidating the molecular physiopathology of acute respiratory distress syndrome in severe acute respiratory syndrome patients

Acute respiratory distress syndrome (ARDS) is a severe form of acute lung injury. It is a response to various diseases of variable etiology, including SARS-CoV infection. To date, a comprehensive study of the genomic physiopathology of ARDS (and SARS) is lacking, primarily due to the difficulty of finding suitable materials to study the disease process at a tissue level (instead of blood, sputa or swaps). Hereby we attempt to provide such study by analyzing autopsy lung samples from patient who died of SARS and showed different degrees of severity of the pulmonary involvement. We performed real-time quantitative PCR analysis of 107 genes with functional roles in inflammation, coagulation, fibrosis and apoptosis; some key genes were confirmed at a protein expression level by immunohistochemistry and correlated to the degree of morphological severity present in the individual samples analyzed. Significant expression levels were identified for ANPEP (a receptor for CoV), as well as inhibition of the STAT1 pathway, IFNs production and CXCL10 (a T-cell recruiter). Other genes unassociated to date with ARDS/SARS include C1Qb, C5R1, CASP3, CASP9, CD14, CD68, FGF7, HLA-DRA, IGF1, IRF3, MALAT-1, MSR1, NFIL3, SLPI, USP33, CLC, GBP1 and TAC1. As a result, we proposed to therapeutically target some of these genes with compounds such as ANPEP inhibitors, SLPI and dexamethasone. Ultimately, this study may serve as a model for future, tissue-based analyses of fibroinflammatory conditions affecting the lung.

Continuous RANKL inhibition in osteoprotegerin transgenic mice and rats suppresses bone resorption without impairing lymphorganogenesis or functional immune responses

Receptor activator of NF-kappaB ligand (RANKL) is an essential mediator of osteoclast formation, function, and survival. The effects of RANKL are inhibited by a soluble decoy receptor called osteoprotegerin (OPG). Total ablation of RANKL in knockout mice leads to high bone mass, lymph node agenesis, and altered lymphocyte differentiation. In contrast, RANKL inhibition via OPG suppresses bone resorption but not inflammation in animal models of inflammatory bone loss. This suggests that the immune phenotype of RANKL knockout mice is related to total RANKL ablation. We hypothesized that prenatal RANKL inhibition via OPG overexpression would suppress bone resorption without influencing lymph node formation or subsequent immune responses. Transgenic rats were created, wherein soluble OPG was overexpressed by 100-fold vs wild type (WT) controls, by gestational day 11 (i.e., before lymph node formation). The structure of lymph nodes, spleen, and thymus of OPG-transgenic (OPG-Tg) animals were comparable to those of age-matched WT rats at gestational day 19 and in adulthood. The OPG-Tg neonates had elevated bone mass, confirming the prenatal inhibition of RANKL. Adult OPG-Tg rats and OPG-Tg mice exhibited no significant functional alterations relative to WT controls when subjected to immune challenges to test for altered innate and humoral responses (e.g., contact hypersensitivity to oxazolone, IgM response to Pneumovax, IgG response to keyhole limpet hemocyanin, or cytokine response to LPS). In summary, prenatal RANKL inhibition did not impair lymph node development, nor did continuous life-long RANKL inhibition cause obvious changes in innate or humoral immune responses in mice or rats.

Translocation of Poly(ethylene glycol-co-hexadecyl)cyanoacrylate Nanoparticles into Rat Brain Endothelial Cells: Role of Apolipoproteins in Receptor-Mediated Endocytosis

Previous in vivo observations in rats have shown that poly(ethylene glycol) polyhexadecylcyanoacrylate (PEG-PHDCA) nanoparticles could translocate into the brain after intravenous injection, which polyhexadecylcyanoacrylate (PHDCA) nanoparticles did not. Through the detailed analysis of the plasma protein adsorption onto the surface of PEG-PHDCA nanoparticles, the present study aimed at clarifying the mechanism by which nanoparticles could penetrate into rat brain endothelial cells (RBEC). Two-dimensional polyacrylamide gel electrophoresis and Western blotting revealed that, after incubation with rat serum, apolipoprotein E (ApoE) adsorbed more onto PEG-PHDCA than on PHDCA nanoparticles. Adsorption of apolipoprotein B-100 (ApoB-100) onto PEG-PHDCA nanoparticles was demonstrated by capillary electrophoresis experiments. Moreover, only when ApoE or ApoB-100 were preadsorbed onto PEG-PHDCA nanoparticles, nanoparticles were found to be more efficient than control nanoparticles for penetrating into RBEC, suggesting the involvement of a low density lipoprotein receptor in this process. Thus, these data clearly demonstrate the involvement of apolipoproteins in the brain transport of PEG-PHDCA nanoparticles, which may open interesting prospects for brain drug delivery.

[Glomerulonephritis with organized immunoglobulin deposits]

Glomerulonephritis with organized immunoglobulin deposits are heterogeneous and may be encountered in a variety of renal disorders. It is particularly important to determine the exact types of immunoglobulin deposited and their monotypy/monoclonality, using specific anti-light chain conjugates and in some instances, anti-heavy chain subclass conjugates. The histologic pattern and identification of monotypic Ig deposits in renal tissue are in some cases sufficient for the diagnosis of AL amyloidosis, type I cryoglobulinic glomerulonephritis or "Randall-type" monoclonal immunoglobulin deposition disease (MIDD). Electron microscopy is particularly valuable for the precise localization of Ig deposits and for determing the pattern of deposition: organized, homogeneous (non-organized or granular) or mixed. New entities in the broad spectrum of Ig deposition diseases are emerging from electron microscopy studies of renal diseases. We propose here a comprehensive classification for diseases featuring the organized deposition in tissues of Ig.

Neuroprotective effects of cardiotrophin-like cytokine on retinal ganglion cells

BACKGROUND

Premature neuronal cell death is a feature of numerous central nervous system and eye diseases, including glaucoma. Neurons (including retinal ganglion cells, RGCs) are protected by several neurotrophic factors, among those the IL-6 family of cytokines. Lately, a novel member of the IL-6 family of cytokines has been identified and cloned. This cytokine is known as novel neurotrophin-1/B-cell-stimulating factor-3 (NNT-1/BSF-3) or cardiotrophin-like cytokine (CLC). It shows neurotrophic as well as B-cell stimulatory effects.

METHODS

In this study, the neuroprotective properties of CLC on RGC loss in vivo were investigated.

RESULTS

CLC significantly protected RGCs from degeneration in both chosen models of retinal neuronal damage: optic nerve crush (P<0.01) and N-methyl-D-aspartate (NMDA) injection (P<0.001).

CONCLUSIONS

CLC shows neuroprotective effects on RGCs in vivo and might be a treatment option for chronic neurodegenerative eye diseases such as glaucoma. Clinical feasibility for the substance requires further investigation since the immunomodulatory and possible adverse effects have not yet been thoroughly characterized.

Cardiotrophin-like cytokine labelling using Bir A biotin ligase: A sensitive tool to study receptor expression by immune and non-immune cells

The recently identified IL-6 family member cardiotrophin-like cytokine (also named novel neurotrophin-1 or B cell stimulating factor-3) forms a secreted complex with cytokine-like factor-1 which binds and activates the tripartite ciliary neurotrophic factor receptor. The striking differences between the phenotype of mice in which either the ciliary neurotrophic factor or its receptor are inactivated suggest that the cardiotrophin-like cytokine/cytokine-like factor-1 complex could be the developmentally important ciliary neurotrophic factor receptor ligand. Cardiotrophin-like cytokine is also produced in the immune system and has been reported to activate B cells in vivo and in vitro. B cells do not express the ciliary neurotrophic factor receptor suggesting the existence of an alternative receptor. We produced the cardiotrophin-like cytokine/cytokine-like factor-1 complex tagged with a Bir A biotin ligase AviTag peptide substrate. This cytokine could be efficiently biotinylated in vitro with Bir A. It was subsequently validated as a sensitive tool for ciliary neurotrophic factor receptor detection by flow cytometry and for magnetic-activated cell sorting. It was also shown to allow the detection of a specific receptor by activated B cells. Whereas binding to cells expressing the ciliary neurotrophic factor receptor could be prevented by competition with ciliary neurotrophic factor, binding to B cells was not. The biotinylated cardiotrophin-like cytokine/cytokine-like factor-1 complex therefore represents a new reagent to study ciliary neurotrophic factor and cardiotrophin-like cytokine receptor expression and for the identification of the putative cardiotrophin-like cytokine B cell receptor. It further validates the use of biotin ligase catalysed biotinylation for the detection of cytokine receptors.

Novel neurotrophin-1/B cell-stimulating factor-3 (NNT-1/BSF-3)/cardiotrophin-like cytokine (CLC)--a novel gp130 cytokine with pleiotropic functions

Novel neurotrophin-1/B-cell stimulating factor-3 (NNT-1/BSF-3) is a new member of the gp130 cytokine family. NNT-1/BSF-3 is a second ligand to the tripartite CNTFR complex and activates Jak-STAT, MAPK and PI3/Akt signaling pathways in various cell systems. So far, the known functions of NNT-1/BSF-3 encompass neurotrophic and B cell stimulatory effects, as well as neuroimmunoendocrine modulation of corticotroph function. Gene expression of NNT-1/BSF-3 is stimulated by PKA- and PKC-dependent pathways. Cellular secretion of NNT-1/BSF-3 requires heteromeric complex formation with other factors, e.g. cytokine-like factor-1 (CLF-1) or soluble ciliary neurotrophic factor receptor (sCNTFR). This article reviews the current knowledge on NNT-1/BSF-3 expression, secretion, receptor interaction, signal transduction and physiologic effects of this novel gp130 cytokine. Remark: After preparation of this manuscript, another novel gp130 cytokine named neuropoietin (NP) has been reported and shown to be a ligand of the CNTFR complex.

IL-6 signal transduction and its physiological roles: the signal orchestration model

Interleukin (IL)-6 is a pleiotropic cytokine that not only affects the immune system, but also acts in other biological systems and many physiological events in various organs. In a target cell, IL-6 can simultaneously generate functionally distinct or sometimes contradictory signals through its receptor complex, IL-6Ralpha and gp130. One good illustration is derived from the in vitro observations that IL-6 promotes the growth arrest and differentiation of M1 cells through gp130-mediated STAT3 activation, whereas the Y759/SHP-2-mediated cascade by gp130 stimulation has growth-enhancing effects. The final physiological output can be thought of as a consequence of the orchestration of the diverse signaling pathways generated by a given ligand. This concept, the signal orchestration model, may explain how IL-6 can elicit proinflammatory or anti-inflammatory effects, depending on the in vivo environmental circumstances. Elucidation of the molecular mechanisms underlying this issue is a challenging subject for future research. Intriguingly, recent in vivo studies indicated that the SHP-2-binding site- and YXXQ-mediated pathways through gp130 are not mutually exclusive but affect each other: a mutation at the SHP-2-binding site prolongs STAT3 activation, and a loss of STAT activation by gp130 truncation leads to sustained SHP-2/ERK MAPK phosphorylation. Although IL-6/gp130 signaling is a promising target for drug discovery for many human diseases, the interdependence of each signaling pathway may be an obstacle to the development of a nonpeptide orally active small molecule to inhibit one of these IL-6 signaling cascades, because it would disturb the signal orchestration. In mice, a consequence of the imbalanced signals causes unexpected results such as gastrointestinal disorders, autoimmune diseases, and/or chronic inflammatory proliferative diseases. However, lessons learned from IL-6 KO mice indicate that IL-6 is not essential for vital biological processes, but a significant impact on disease progression in many experimental models for human disorders. Thus, IL-6/gp130 signaling will become a more attractive therapeutic target for human inflammatory diseases when a better understanding of IL-6 signaling, including the identification of the conductor for gp130 signal transduction, is achieved.

Regulatory effects of osteoprotegerin on cellular and humoral immune responses

The interaction between receptor activator of nuclear factor-kappaB ligand (RANKL) and RANK has been reported to regulate immunity in addition to bone metabolism. The aim of this study was to determine if osteoprotegerin (OPG), an inhibitor of the RANKL-RANK interaction and possibly a new drug against osteoporosis, would adversely affect immunity. OPG was used to treat mice developing different models of cellular and humoral immune responses and also in vitro in T and B cell assays. In mice, OPG does not affect cell-mediated reactions such as contact hypersensitivity to the hapten oxazolone and liver damage, granuloma formation, and infectious load induced by mycobacterial infection. However, OPG increases humoral reactions such as the production of IgM, IgG, and IgE against the T cell dependent antigen keyhole limpet hemocyanin and the production of IgM against the T cell independent antigen Pneumovax. In vitro, OPG modestly co-stimulates T cells but does not affect the proliferation of B cells. OPG has modest immunoregulatory effects that seem to be confined to the humoral response to specific antigens.

Expression of novel neurotrophin-1/B-cell stimulating factor-3 (NNT-1/BSF-3) in murine pituitary folliculostellate TtT/GF cells: pituitary adenylate cyclase-activating polypeptide and vasoactive intestinal peptide-induced stimulation of NNT-1/BSF-3 is mediated by protein kinase A, protein kinase C, and extracellular-signal-regulated kinase1/2 pathways

Novel neurotrophin-1/B cell stimulating factor-3 (NNT-1/BSF-3) is a gp130 cytokine potently stimulating corticotroph proopiomelanocortin gene expression and ACTH secretion by a Janus kinase-signal transducer and activator of transcription (JAK-STAT)-dependent mechanism. In the current study, we examined the regulation of NNT-1/BSF-3 mRNA expression in murine pituitary folliculostellate TtT/GF cells using Northern blot technique. A 5- to 9-fold and a 4- to 7-fold induction in NNT-1/BSF-3 mRNA expression was observed between 2 and 6 h stimulation with the protein kinase C (PKC) stimulus phorbol-12-myristate-13-acetate (100 nm) and the protein kinase A (PKA) stimulus Bu(2)cAMP (5 mm), respectively. Pituitary adenylate cyclase-activating polypeptide (PACAP-38, 50 nm) and vasoactive intestinal peptide (VIP, 50 nm) also stimulated NNT-1/BSF-3 mRNA expression 5- to 9-fold between 2 and 6 h. Preincubation with PKC and PKA inhibitors such as H-7 (20 microm), GF109203X (50 microm), and H-89 (50 microm) decreased the stimulatory effects of PACAP and VIP. Both PACAP-38 and VIP also rapidly induced ERK1/2 phosphorylation and their stimulatory effect on NNT-1/BSF-3 mRNA expression was reduced by the MAPK kinase/ERK kinase (MEK) inhibitor U0126 (10 microm). Dexamethasone (10(-7) m) was a potent inhibitor of phorbol-12-myristate-13-acetate-induced NNT-1/BSF-3 expression. RT-PCR analysis demonstrated TtT/GF cells to express the short and the hop variant but not the hip variant of the PACAP-1 receptor (PAC1-R). In addition, TtT/GF cells express the VIP/PACAP-2 receptor (VPAC2-R). In summary, NNT-1/BSF-3 is expressed in pituitary folliculostellate TtT/GF cells and induced by PKC-, PKA-, and ERK1/2-dependent mechanisms. The novel gp130 cytokine NNT-1/BSF-3 derived from folliculostellate cells might act as a paracrine neuroimmunoendocrine modulator of pituitary corticotroph function.

Functional significance of novel neurotrophin-1/B cell-stimulating factor-3 (cardiotrophin-like cytokine) for human myeloma cell growth and survival

Cytokines of the gp130 family, particularly interleukin 6 (IL-6), play a central role in the growth and survival of malignant plasma cells. Recently, novel neurotrophin-1 (NNT-1)/B cell-stimulating factor-3 (BSF-3), also reported as cardiotrophin-like cytokine (CLC), was identified as a cytokine belonging to the gp130 family. BSF-3, similar to IL-6, exerts regulatory effects on normal B cell functions, but its functional significance in haematological malignancies has not been defined. The purpose of this study was to evaluate the biological effects and signalling pathways that are induced by BSF-3 in malignant plasma cells. Recombinant human BSF-3 was found to have growth stimulatory activity on plasmacytoma cell lines and primary tumour cells. In addition, BSF-3 was able to protect from Dexamethasone (Dex)-induced apoptosis. BSF-3 stimulated cell growth could not be inhibited by neutralizing anti-IL-6 or anti-IL-6 receptor antibodies, but was abrogated by anti-gp130 antibodies. In INA-6.Tu11 cells, a subline of the IL-6-dependent human plasma cell line INA-6 expressing gp130 and the receptor for leukaemia inhibitory factor (LIF), stimulation with BSF-3 induced tyrosine phosphorylation of signal transducer and activator of transcription 3 (STAT3). AG490, an inhibitor of Janus kinases, decreased BSF-3 induced cell growth in a dose-dependent manner. This correlated with a reduction of STAT3 phosphorylation levels, while p44/42 mitogen-activated protein kinase (MAPK) phosphorylation was not affected. In conclusion, BSF-3 is a novel myeloma growth and survival factor with a potential role in the pathophysiology of the disease.