Downregulation of immunoglobulin-like transcript-4 (ILT4) in patients with psoriatic arthritis

Dexamethasone promotes renal fibrosis by upregulating ILT4 expression in myeloid-derived suppressor cells

Studies have shown that adoptive transfer of myeloid-derived suppressor cells (MDSCs) can alleviate various inflammatory diseases, including glomerulonephritis, but the long-term effects of the transferred MDSCs are still unclear. In addition, although glucocorticoids exert immunosuppressive effects on inflammatory diseases by inducing the expansion of MDSCs, the impact of glucocorticoids on the immunosuppressive function of MDSCs and their molecular mechanisms are unclear. In this study, we found that adoptive transfer of MDSCs to doxorubicin-induced focal segmental glomerulosclerosis (FSGS) mice for eight consecutive weeks led to an increase in serum creatinine and proteinuria and aggravation of renal interstitial fibrosis. Similarly, 8 weeks of high-dose dexamethasone administration exacerbated renal interstitial injury and interstitial fibrosis in doxorubicin-induced mice, manifested as an increase in serum creatinine and proteinuria, collagen deposition and α-SMA expression. On this basis, we found that dexamethasone could enhance MDSC expression and secretion of the fibrosis-related cytokines TGF-β and IL-10. Mechanistically, we revealed that dexamethasone promotes the expression of immunoglobulin-like transcription factor 4 (ILT4), which enhances the T-cell inhibitory function of MDSCs and promotes the activation of STAT6, thereby strengthening the expression and secretion of TGF-β and IL-10. Knocking down ILT4 alleviated renal fibrosis caused by adoptive transfer of MDSCs. Therefore, our findings demonstrate that the role and mechanism of dexamethasone mediate the expression and secretion of TGF-β and IL-10 in MDSCs by promoting the expression of ILT4, thereby leading to renal fibrosis.

Characterization and functional analyses of novel chicken leukocyte immunoglobulin-like receptor subfamily B members 4 and 5

The inhibitory leukocyte immuno-globulin-like receptors (LILRBs) play an important role in innate immunity. Currently, no data exist regarding the role of LILRB4 and LILRB5 in the activation of immune signaling pathways in mammalian and avian species. Here, we report for the first time, the cloning and structural and functional analyses of chicken LILRB4–5 genes identified from 2 genetically disparate chicken lines. Comparison of LILRB4–5 amino acid sequences from lines 6.3 and 7.2 with those of mammalian proteins revealed 17 to 62% and 19 to 29% similarity, respectively. Phylogenetic analysis indicated that the chicken LILRB4–5 genes were closely associated with those of other species. LILRB4–5 could be subdivided into 2 groups having distinct immunoreceptor tyrosine-based inhibitory motifs, which bind to Src homology 2-containing tyrosine phosphatase 2 (SHP-2). Importantly, LILRB4–5 also upregulated the major histocompatibility complex (MHC) class I and β2-microglobulin gene expression as well as the expression of transporter associated with antigen processing 1–2, which play an important role in MHC class I activation. Our results indicate that LILRB4–5 are transcriptional regulators of the MHC class I pathway components and regulate innate immune responses. Furthermore, LILRB4–5 could activate the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway genes in macrophages and induce the expression of chemokines and T helper (Th)1, Th2, and Th17 cytokines. Our data suggest that LILRB4–5 are innate immune receptors associated with SHP-2, MHC class I, and β2-microglobulin. Additionally, they activate the JAK/STAT signaling pathway and control the expression of cytokines in macrophages.

The Role of Immune Checkpoint Receptors in Regulating Immune Reactivity in Lupus

Immune checkpoint receptors with co-stimulatory and co-inhibitory signals are important modulators for the immune system. However, unrestricted co-stimulation and/or inadequate co-inhibition may cause breakdown of self-tolerance, leading to autoimmunity. Systemic lupus erythematosus (SLE) is a complex multi-organ disease with skewed and dysregulated immune responses interacting with genetics and the environment. The close connections between co-signaling pathways and SLE have gradually been established in past research. Also, the recent success of immune checkpoint blockade in cancer therapy illustrates the importance of the co-inhibitory receptors in cancer immunotherapy. Moreover, immune checkpoint blockade could result in substantial immune-related adverse events that mimic autoimmune diseases, including lupus. Together, immune checkpoint regulators represent viable immunotherapeutic targets for the treatment of both autoimmunity and cancer. Therefore, it appears reasonable to treat SLE by restoring the out-of-order co-signaling axis or by manipulating collateral pathways to control the pathogenic immune responses. Here, we review the current state of knowledge regarding the relationships between SLE and the co-signaling pathways of T cells, B cells, dendritic cells, and neutrophils, and highlight their potential clinical implications. Current clinical trials targeting the specific co-signaling axes involved in SLE help to advance such knowledge, but further in-depth exploration is still warranted.

Chicken novel leukocyte immunoglobulin-like receptor subfamilies B1 and B3 are transcriptional regulators of major histocompatibility complex class I genes and signaling pathways

Objective

The inhibitory leukocyte immunoglobulin-like receptors (LILRBs) play an important role in innate immunity. The present study represents the first description of the cloning and structural and functional analysis of LILRB1 and LILRB3 isolated from two genetically disparate chicken lines.

Methods

Chicken LILRB1-3 genes were identified by bioinformatics approach. Expression studies were performed by transfection, quantitative polymerase chain reaction. Signal transduction was analyzed by western blots, immunoprecipitation and flow cytometric. Cytokine levels were determined by enzyme-linked immunosorbent assay.

Results

Amino acid homology and phylogenetic analyses showed that the homologies of LILRB1 and LILRB3 in the chicken line 6.3 to those proteins in the chicken line 7.2 ranged between 97%–99%, while homologies between chicken and mammal proteins ranged between 13%–19%, and 13%–69%, respectively. Our findings indicate that LILRB1 and LILRB3 subdivided into two groups based on the immunoreceptor tyrosine-based inhibitory motifs (ITIM) present in the transmembrane domain. Chicken line 6.3 has two ITIM motifs of the sequence LxYxxL and SxYxxV while line 7.2 has two ITIM motifs of the sequences LxYxxL and LxYxxV. These motifs bind to SHP-2 (protein tyrosine phosphatase, non-receptor type 11) that plays a regulatory role in immune functions. Moreover, our data indicate that LILRB1 and LILRB3 associated with and activated major histocompatibility complex (MHC) class I and β2-microglobulin and induced the expression of transporters associated with antigen processing, which are essential for MHC class I antigen presentation. This suggests that LILRB1 and LILRB3 are transcriptional regulators, modulating the expression of components in the MHC class I pathway and thereby regulating immune responses. Furthermore, LILRB1 and LILRB3 activated Janus kinase2/tyrosine kinase 2 (JAK2/TYK2); signal transducer and activator of transcription1/3 (STAT1/3), and suppressor of cytokine signaling 1 genes expressed in Macrophage (HD11) cells, which induced Th1, Th2, and Th17 cytokines.

Conclusion

These data indicate that LILRB1 and LILRB3 are innate immune receptors associated with SHP-2, MHC class I, β2-microglobulin, and they activate the Janus kinase/signal transducer and activator of transcription signaling pathway. Thus, our study provides novel insights into the regulation of immunity and immunopathology.

Synovial fluid from patients with rheumatoid arthritis modulates monocyte cell-surface phenotype

Objectives

To investigate the ability of synovial fluid from patients with rheumatoid arthritis (RA) or osteoarthritis (OA) to modulate cell-surface phenotype, function and viability of monocytes.

Methods

Monocytes from healthy donors were incubated with synovial fluid from patients with RA or OA. These were then cultured with autologous healthy CD4+ T-cells. Immunoglobulin-like transcript 4 (ILT4) and CD86 were evaluated on stimulated monocytes and CD4+ T-cells via fluorescence activated cell sorting.

Results

Monocytes incubated with synovial fluid from patients with RA (SF-RA; n = 12) had significantly lower ILT4 and higher CD86 levels than those incubated with synovial fluid from patients with OA (SF-OA; n = 12) or medium alone. In patients with RA, there was a significant negative correlation between ILT4 and disease activity score (DAS; r = −0.699), and a positive correlation between CD86 and DAS (r = 0.626). T-cells costimulated with monocytes cultured with SF-RA produced significantly more interferon-γ and tumour necrosis factor-α than those costimulated with monocytes cultured with SF-OA or controls.

Conclusions

Soluble mediators in SF-RA could contribute to modulating inflammation and local effectiveness of the immune response.

Analysis of the Expression and Function of Immunoglobulin-Like Transcript 4 (ILT4, LILRB2) in Dendritic Cells from Patients with Systemic Lupus Erythematosus

Dendritic cells (DC) play an important role in the development and maintenance of immune tolerance. Although the inhibitory receptor ILT4/LILRB2 has been related with the tolerogenic phenotype of DC, the possible role of this receptor in the breakdown of DC tolerogenic function in systemic lupus erythematosus (SLE) has not been elucidated. In this study, we analyzed the expression and function of the inhibitory receptor ILT4 in DC from SLE patients. We found that the percentage of ILT4 positive plasmacytoid DC and myeloid DC is significantly diminished in SLE patients. Interestingly, ligation of ILT4 did not affect the maturation or immunogenic capability of DC in healthy controls. In contrast, in SLE patients we observed an inhibitory effect of ILT4 on the immunogenic capability of DC. ILT4 was shown not to have a crucial role in regulating the maturation and function of DC from healthy controls but is partially involved in the maturation process and immunogenic capability of DC from SLE patients, suggesting that other inhibitory receptors, involved in the regulation of DC tolerogenic function, may be impaired in this autoimmune disease.

Differential Antigen-presenting B Cell Phenotypes from Synovial Microenvironment of Patients with Rheumatoid and Psoriatic Arthritis

OBJECTIVE

To study the qualitative and quantitative phenotypic changes that occur in molecules involved in antigen presentation and costimulation in synovial B cells from rheumatoid arthritis (RA) and psoriatic arthritis (PsA).

METHODS

The presence of HLA-DR, CD86, and CD40 in CD20+ cells was studied in RA synovium biopsies using immunohistochemistry and immunofluorescence. Expression was assessed by flow cytometry of the Class II molecules CD40, CD86, CD23, and CD27 on B cells from the synovial fluid (SF), with respect to peripheral blood, from 13 patients with RA and 15 patients with PsA. Expression of interferon-induced protein with tetratricopeptide repeats 4 (IFIT4) in immune-selected CD20+ cells from patients with RA was assessed by quantitative realtime PCR.

RESULTS

Infiltrating synovial RA, B cells expressed HLA-DR, CD40, and CD86. Increased expression of CD86, HLA-DR, and HLA-DQ in B cells from SF was found in patients with RA and PsA. HLA-DP was also elevated in rheumatoid SF B cells; conversely, a significantly lower expression was observed in SF from patients with PsA. CD40 expression was increased in SF B cells from PsA, but not in patients with RA. Interestingly, CD20 surface expression level was significantly lower in SF B cells (CD19+, CD138-) from RA, but not in patients with PsA. CD27 upregulation and CD23 downregulation were observed in synovial B cells in both pathologies. Finally, a 4-fold increase in IFIT4 mRNA content was shown in B cells from SF in patients with RA.

CONCLUSION

Synovial B cells from patients with RA and patients with PsA express different antigen-presenting cell phenotypes, suggesting that this cell type plays a dissimilar role in the pathogenesis of each disease.