Upregulated Fcrl5 disrupts B cell anergy and causes autoimmune disease

Identification of genetic indicators linked to immunological infiltration in idiopathic pulmonary fibrosis

This study employed bioinformatics to investigate potential molecular markers associated with idiopathic pulmonary fibrosis (IPF) and examined their correlation with immune-infiltrating cells. Microarray data for IPF were retrieved from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) and module genes were identified through Limma analysis and weighted gene co-expression network analysis. Enrichment analysis and protein-protein interaction network development were performed on the DEGs. Machine learning algorithms, including least absolute shrinkage and selection operator regression, random forest, and extreme gradient boosting, were applied to identify potential key genes. The predictive accuracy was assessed through a nomogram and a receiver operating characteristic (ROC) curve. Additionally, the correlation between core genes and immune-infiltrating cells was assessed utilizing the CIBERSORT algorithm. An IPF model was established in a human fetal lung fibroblast 1 (HFL-1) through induction with transforming growth factor β1 (TGF-β1), and validation was conducted via reverse transcription-quantitative polymerase chain reaction. A sum of 1246 genes exhibited upregulation, whereas 879 genes were downregulated. Pathway enrichment analysis and functional annotation revealed that DEGs were predominantly involved in extracellular processes. Four key genes - cd19, cxcl13, fcrl5, and slamf7 - were identified. Furthermore, ROC analysis demonstrated high predictive accuracy for these 4 genes. Compared to healthy individuals, lung tissues from IPF patients exhibited an increased presence of plasma cells, CD4 memory-activated T cells, M0 macrophages, activated dendritic cells, resting NK cells, and M2 macrophage infiltration. The upregulation of cd19, cxcl13, fcrl5, and slamf7 in TGF-β1-treated HFL-1 cells was confirmed, aligning with the findings from the microarray data analysis. cd19, cxcl13, fcrl5, and slamf7 serve as diagnostic markers for IPF, providing fresh perspectives regarding the fundamental pathogenesis and molecular mechanisms associated with this condition.

Gene Expression Differences Based on Low Total 25(OH)D and Low VDBP Status with a Preterm Birth

Preterm birth (PTB; <37 weeks' gestation) is a persistent problem in the United States that affects non-Hispanic Black women at much higher rates than White women. Several biomarkers have been associated with PTB, including vitamin D deficiency (VDD) and low levels of vitamin D-binding protein (VDBP). However, no biomarker has been found to predict PTB. To identify a predictive biomarker of PTB, gene expression differences were determined in Black women with PTB and full-term births and between women with high and low levels of plasma vitamin D and high and low VDBP levels. In this pilot study of 19 pregnant women from the Biosocial Impact on Black Births (BIBB) study, we found that 47 genes were upregulated and 16 genes were downregulated in women with PTB as compared with women who had a full-term birth, 361 genes were downregulated and 61 genes were upregulated in women with VDD as compared with those that had vitamin D sufficiency, and 44 genes were upregulated and 295 were downregulated in women with low VDBP. Several genes expressed by neutrophils were downregulated in the PTB, VDD, and low VDBP groups. These findings support the idea that vitamin D and VDBP status may be important clinical markers influencing the gene expression of genes associated with PTB.

Critical roles of chronic BCR signaling in the differentiation of anergic B cells into age-associated B cells in aging and autoimmunity

Age-associated B cells (ABCs) with autoreactive properties accumulate with age and expand prematurely in autoimmune diseases. However, the mechanisms behind ABC generation and maintenance remain poorly understood. We show that continuous B cell receptor (BCR) signaling is essential for ABC development from anergic B cells in aged and autoimmune mice. ABCs exhibit constitutive BCR activation, with surface BCRs being internalized. Notably, anergic B cells, but not nonautoreactive B cells, contributed to ABC formation in these models. Anergic B cells also showed a greater propensity for in vitro differentiation into ABCs, which was inhibited by the expression of the transcription factor Nr4a1. Bruton's tyrosine kinase (Btk), a key BCR signaling component, was constitutively activated in ABCs from aged and autoimmune mice as well as patients with lupus. Inhibiting Btk reduced ABC numbers and ameliorated the pathogenicity of lupus mice. Our findings reveal critical mechanisms underlying ABC development and offer previously unrecognized therapeutic insights for autoimmune diseases.

Age-Associated B Cells in Autoimmune Diseases: Pathogenesis and Clinical Implications

As a heterogeneous B cell subset, age-associated B cells (ABCs) exhibit distinct transcription profiles, extrafollicular differentiation processes, and multiple functions in autoimmunity. TLR7 and TLR9 signals, along with IFN-γ and IL-21 stimulation, are both essential for ABC differentiation, which is also regulated by chemokine receptors including CXCR3 and CCR2 and integrins including CD11b and CD11c. Given their functions in antigen uptake and presentation, autoantibody and proinflammatory cytokine secretion, and T helper cell activation, ABCs display potential in the prognosis, diagnosis, and therapy for autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, Sjögren's syndrome, multiple sclerosis, neuromyelitis optica spectrum disorders, and ankylosing spondylitis. Specifically targeting ABCs by inhibiting T-bet and CD11c and activating CD11b and ARA2 represents potential therapeutic strategies for SLE and RA. Although single-cell sequencing technologies have recently revealed the heterogeneous characteristics of ABCs, further investigations to explore and validate ABC-target therapies are still warranted.

The role of B cells in the pathogenesis of type 1 diabetes

Type 1 diabetes (T1D) is a metabolic disorder caused by a complete lack of insulin, primarily manifested by hyperglycemia. The mechanisms underlying the onset of T1D are complex, involving genetics, environment, and various unknown factors, leading to the infiltration of various immune components into the islets. Besides T cells, B cells are now considered important contributors to the pathogenesis of T1D, according to recent studies. In non-obese diabetic (NOD) mice, the absence of B cells prevents the development of T1D, and B-cell depletion can even restore the function of pancreatic β cells, emphasizing their involvement in the development of T1D. Naturally, besides pathogenic B cells, regulatory B cells (Bregs) might have a protective function in T1D. This article examines the mechanisms behind B-cell tolerance and the defects in B-cell tolerance checkpoints in T1D. We explored possible functions of B cells in T1D, including the role of islet autoantibodies in T1D, T-B cell interactions, and the role of Bregs in the pathogenesis of T1D. We also summarized the advances of B cell-targeted therapy, exploring new methods for intervention and treatment of T1D.

Polymorphisms of B-lymphocyte-associated genes CD20 and FCRL5 are associated with susceptibility to autoimmune thyroid diseases

BACKGROUND

Recent studies have confirmed that B cell-related genes CD20 and FCRL5 may be involved in the pathogenesis of autoimmune thyroid diseases (AITDs). However, there is a lack of comprehensive genetic susceptibility studies on this subject.

OBJECTIVE

The purpose of this study was to investigate the relationship of CD20 and FCRL5 gene polymorphisms with AITD susceptibility.

METHODS

A total of 1740 subjects were recruited from the Chinese Han population. They consisted of 1007 patients with AITD and 633 healthy controls. Multiplex polymerase chain reaction (PCR) combined with high-throughput sequencing was used to genotype four screened single nucleotide polymorphisms (SNPs). The four SNPs were rs7126354 of CD20 and rs6667109, rs6692977 and rs3811035 of FCRL5.

RESULTS

The minor allele frequency of rs7126354 was significantly lower in patients with AITD and Hashimoto's thyroiditis (HT) than in healthy controls (P = 0.031; P = 0.017). The minor allele frequency of rs6667109 was significantly higher in the Graves' disease (GD) subgroup than in the healthy control group (P = 0.029). In the Log-additive model, rs6667109 in the GD group also showed an increased risk of onset disease.

CONCLUSIONS

This study presents robust evidence of a genetic association of CD20 and FCRL5 with AITDs. The C allele of CD20 rs7126354 is a protective factor for HT susceptibility. The A allele of FCRL5 rs6667109 is a risk factor for the susceptibility to GD.

Humoral responses are enhanced by facilitating B cell viability by Fcrl5 overexpression in B cells

B cell initial activity is regulated through a balance of activation and suppression mediated by regulatory molecules expressed in B cells; however, the molecular mechanisms underlying this process remain incompletely understood. In this study, we investigated the function of the Fc receptor-like (Fcrl) family molecule Fcrl5, which is constitutively expressed in naive B cells, in humoral immune responses. Our study demonstrated that B cell-specific overexpression of Fcrl5 enhanced antibody (Ab) production in both T cell-independent type 1 (TI1) and T cell-dependent (TD) responses. Additionally, it promoted effector B cell formation under competitive conditions in TD responses. Mechanistically, in vitro ligation of Fcrl5 by agonistic Abs reduced cell death and enhanced proliferation in lipopolysaccharide-stimulated B cells. In the presence of anti-CD40 Abs and IL-5, the Fcrl5 ligation not only suppressed cell death but also enhanced differentiation into plasma cells. These findings reveal a novel role of Fcrl5 in promoting humoral immune responses by enhancing B cell viability and plasma cell differentiation.

Gene expression and alternative splicing analysis in a large-scale Multiple Sclerosis study

Background

Multiple Sclerosis (MS) is an autoimmune neurodegenerative disease affecting approximately 3 million people globally. Despite rigorous research on MS, aspects of its development and progression remain unclear. Understanding molecular mechanisms underlying MS is crucial to providing insights into disease pathways, identifying potential biomarkers for early diagnosis, and revealing novel therapeutic targets for improved patient outcomes.

Methods

We utilized publicly available RNA-seq data (GSE138614) from post-mortem white matter tissues of five donors without any neurological disorder and ten MS patient donors. This data was interrogated for differential gene expression, alternative splicing and single nucleotide variants as well as for functional enrichments in the resulting datasets.

Results

A comparison of non-MS white matter (WM) to MS samples yielded differentially expressed genes involved in adaptive immune response, cell communication, and developmental processes. Genes with expression changes positively correlated with tissue inflammation were enriched in the immune system and receptor interaction pathways. Negatively correlated genes were enriched in neurogenesis, nervous system development, and metabolic pathways. Alternatively spliced transcripts between WM and MS lesions included genes that play roles in neurogenesis, myelination, and oligodendrocyte differentiation, such as brain enriched myelin associated protein (BCAS1), discs large MAGUK scaffold protein 1 (DLG1), KH domain containing RNA binding (QKI), and myelin basic protein (MBP). Our approach to comparing normal appearing WM (NAWM) and active lesion (AL) from one donor and NAWM and chronic active (CA) tissues from two donors, showed that different IgH and IgK gene subfamilies were differentially expressed. We also identified pathways involved in white matter injury repair and remyelination in these tissues. Differentially spliced genes between these lesions were involved in axon and dendrite structure stability. We also identified exon skipping events and spontaneous single nucleotide polymorphisms in membrane associated ring-CH-type finger 1 (MARCHF1), UDP glycosyltransferase 8 (UGT8), and other genes important in autoimmunity and neurodegeneration.

Conclusion

Overall, we identified unique genes, pathways, and novel splicing events affecting disease progression that can be further investigated as potential novel drug targets for MS treatment.