[The CD40-CD40L axis: Current and future implications in clinical immunology]

CD40 induces PIR-A+ macrophages to promote chronic allograft rejection

BACKGROUND

Chronic rejection is the leading cause of progressive allograft function decline. Studies have demonstrated that CD40-CD40L-induced paired immunoglobulin-like receptor-A (PIR-A) is the MHC-I receptor necessary for the specific memory response in macrophages of mice with chronic rejection. However, the underlying mechanisms remain unclear.

METHODS

BALB/c mouse hearts were transplanted into C57BL/6, RelB-/- or LysMCrePirafl/fl mice, and a chronic rejection model was established by injecting CTLA-4-Ig. CD40-CD40L blockade in recipients by injecting anti-CD40L antibody. Allograft survival was monitored and histologically was assessed. Bone marrow-derived macrophages were treated with an anti-CD40 antibody. PIR-A expression was assessed via various methods in vivo and in vitro. Transcription factor expression levels were detected using RNA sequencing. DNA specifically bound to transcription factors was detected using ChIP-seq.

RESULTS

CD40 and PIR-A were highly expressed and colocalized in macrophage-infiltrating allograft in the mouse model. CD40-CD40L blockade inhibited PIR-A expression and prolonged allograft survival. Conditional deletion of Pira in recipient's macrophages inhibited chronic rejection and promoted long-term allograft acceptance. Mechanistically, CD40 may activate transcription factor NF-κB2 translocation into the nucleus to up-regulate PIR-A expression, promoting chronic rejection of cardiac transplantation. NF-κB2 regulated PIR-A expression by binding to the intergenic region of Pira.

CONCLUSIONS

Our data suggest that Pira is a potential target to induce long-term allograft tolerance. CD40 may activate transcription factor NF-κB2 translocation into the nucleus to up-regulate PIR-A expression, promoting chronic rejection of cardiac transplantation. The study findings provide novel therapeutic opportunities to promote transplant survival in clinical settings.

Frexalimab (SAR441344) as a potential multiautoimmune disorder tackling mAB targeting the CD40-CD40L pathway undergoing clinical trials: a review

Autoimmune disorders exhibit intricate pathology. Their mechanisms are complex, which attenuates the need for novel therapeutic interventions. Frexalimab, a potent monoclonal antibody targeting the dysregulated CD40-CD40L pathway, stands out as a formidable weapon against the assault of inflammation and tissue devastation. Diverse electronic databases were searched using relevant keywords to extract data on the role of Frexalimab in combating various autoimmune diseases. This review highlights Frexalimab's efficacy in improving various disability indicators of relapsing multiple sclerosis (RMS), alleviating fatigue in primary Sjögren's syndrome (PSJS), and improving glycemic control in diabetic patients. Across multiple trials, its favorable safety profile has proven its superiority over first-generation drugs in minimizing side effects. Indeed, Frexalimab has become a harbinger of hope in the fight against autoimmune diseases and has pioneered a unique and unchallenging way for tackling complex autoimmune diseases in the clinical realm, however, further large-scale trials are needed to establish its therapeutic benefits across different autoimmune conditions.

Involvement of CD40-CD40L and ICOS-ICOSL in the development of chronic rhinosinusitis by targeting eosinophils

Background

Chronic rhinosinusitis (CRS), whose prevalence and pathogenesis are age-related, is characterized by nasal tissue eosinophil infiltration. CD40-CD40 ligand (CD40L) pathway involves in the eosinophil-mediated inflammation, and inducible co-stimulator (ICOS)-ICOS ligand (ICOSL) signal can strengthen CD40-CD40L interaction. Whether CD40-CD40L and ICOS-ICOSL have a role in the development of CRS remains unknown.

Objectives

The aim of this study is to investigate the association of CD40-CD40L and ICOS-ICOSL expression with CRS and underlying mechanisms.

Methods

Immunohistology detected the expression of CD40, CD40L, ICOS, and ICOSL. Immunofluorescence was performed to evaluate the co-localizations of CD40 or ICOSL with eosinophils. Correlations between CD40-CD40L and ICOS-ICOSL as well as clinical parameters were analyzed. Flow cytometry was used to explore the activation of eosinophils by CD69 expression and the CD40 and ICOSL expression on eosinophils.

Results

Compared with the non-eCRS subset, ECRS (eosinophilic CRS) subset showed significantly increased CD40, ICOS, and ICOSL expression. The CD40, CD40L, ICOS, and ICOSL expressions were all positively correlated with eosinophil infiltration in nasal tissues. CD40 and ICOSL were mainly expressed on eosinophils. ICOS expression was significantly correlated with the expression of CD40-CD40L, whereas ICOSL expression was correlated with CD40 expression. ICOS-ICOSL expression positively correlated with blood eosinophils count and disease severity. rhCD40L and rhICOS significantly enhanced the activation of eosinophils from patients with ECRS. Tumor necrosis factor-α (TNF-α) and interleukin-5 (IL-5) obviously upregulated CD40 expression on eosinophils, which was significantly inhibited by the p38 mitogen-activated protein kinase (MAPK) inhibitor.

Conclusions

Increased CD40-CD40L and ICOS-ICOSL expressions in nasal tissues are linked to eosinophils infiltration and disease severity of CRS. CD40-CD40L and ICOS-ICOSL signals enhance eosinophils activation of ECRS. TNF-α and IL-5 regulate eosinophils function by increasing CD40 expression partly via p38 MAPK activation in patients with CRS.

CD40 Agonist Monoclonal Antibody-Mediated Hepatitis in TNF-Receptor 1 Gene Knockout Mice

Tumor necrosis factor-alpha (TNF-α) plays an important role in liver inflammation. CD40-CD40 ligand (CD40-CD40L) is a key receptor–ligand signaling pair involved in the adaptive immune response and pathogenesis of autoimmune diseases. In mice, CD40 activation leads to sickness behavior syndrome (SBS) comprising weight loss, sleep disruption and depression, which can be blocked by administration of the TNF-inhibitor etanercept. In the present study, we assessed the extent of hepatic inflammation in mice devoid of the TNF-receptor 1 (TNFR1)-mediated signaling pathway. The TNFR1-depleted (TNFR1−/−) adult mice and their wild type littermates were given a single intra-peritoneal injection of CD40 agonist monoclonal antibody (mAb) or rat IgG2a isotope control. As described previously, TNFR1−/− mice were protected from SBS upon CD40 mAb treatment. Cd40, tnf and tnfr1 mRNA and Tnf-α peptide were increased in the liver of CD40 mAb-stimulated wild type mice. Serum alanine aminotransferase was elevated in both CD40-activated wild type and TNFR1−/− mice. TNFR1−/− mice showed much less intra-parenchymal infiltrates, hepatocellular necrosis, and perivascular clusters upon CD40 mAb activation than their wild type littermates. A gene expression microarray detected increased activity of metabolic and detoxification pathways and decreased activity of inflammatory pathways. We conclude that immune activation and development of liver inflammation in CD40L interactions depend on TNFR1-mediated signaling pathways and are counteracted by alterations in metabolic pathways.