IL-10/IL-10RA signaling pathway: From immune regulation hub to innovative biomedical target

I. Introduction

Interleukin-10 (IL-10) is a key anti-inflammatory cytokine in the immune system, primarily secreted by regulatory T cells, monocytes, macrophages, and dendritic cells. The biological function of IL-10 depends on its binding to the specific receptor IL-10RA. IL-10RA is the ligand-binding subunit of the IL-10 receptor complex, forming a functional heterotetrameric receptor with the auxiliary subunit IL-10RB. The IL-10/IL-10RA signaling axis mediates immune suppression and inflammation regulation through the JAK-STAT3 pathway.

Recent advances in understanding the molecular mechanisms of IL-10/IL-10RA have highlighted its dual value in autoimmune disease treatment, tumor immunotherapy, and monogenic disorder research. High-throughput detection technologies like TR-FRET enable precise analysis of ligand-receptor interactions, providing powerful tools for drug screening and mechanistic studies.

II. Molecular Basis and Function of IL-10/IL-10RA Signaling

IL-10 is a protein encoded by the IL-10 gene on chromosome 1, consisting of two 160-amino acid peptide chains forming a 36 kDa homodimer. The IL-10 receptor has two subunits: IL-10RA and IL-10RB.

Upon binding to IL-10RA, IL-10 activates JAK1 and TYK2, leading to phosphorylation of IL-10RA and subsequent STAT3 phosphorylation. This causes STAT3 dimerization, nuclear translocation, and transcription of target genes, ultimately expressing anti-inflammatory effectors. IL-10 inhibits dendritic cell maturation and antigen presentation, suppresses TLR-mediated MyD88-dependent pathways, and reduces pro-inflammatory cytokines like IL-6, IL-1β, and TNF. These processes are critical for maintaining gastrointestinal immune homeostasis.

From an evolutionary perspective, the IL-10 signaling system emerged in early vertebrates, with IL-10 receptors originating in cartilaginous fish ~450 million years ago and IL-10 ligands diversifying in bony fish ~400 million years ago. Functional differentiation produced subgroups like immunosuppressive (IL-10), barrier-protective, and antiviral types, all highly conserved.

III. Dual Roles of IL-10/IL-10RA Signaling in Disease

Very early-onset inflammatory bowel disease (VEO-IBD) and IL-10RA mutations. IL-10 receptor mutations are the most common monogenic cause of VEO-IBD, accounting for ~15% of pediatric IBD cases. IL-10RA variants disrupt signaling, increasing TNF and other pro-inflammatory cytokines in peripheral blood mononuclear cells and causing severe intestinal inflammation. Patients typically present with refractory diarrhea or recurrent oral ulcers within the first year of life; hematopoietic stem cell transplantation is currently the most effective treatment.

IL-10's complex role in the tumor microenvironment. In glioblastoma, tumor-associated macrophages (TAMs) often exhibit an M2-like phenotype. Myeloid-specific IL-10RA knockout suppresses tumor growth by shifting M2 to M1 polarization via reduced STAT3 phosphorylation. Bacterial immunotherapy exploits delayed IL-10R expression to drive tumor-infiltrating immune cells into an IL-10Rhi state, evading phagocytosis while expanding exhausted CD8+ T cells, effectively clearing tumors and preventing metastasis.

IL-10 family cytokines in respiratory diseases. IL-10 exhibits dual roles in asthma, COPD, pulmonary fibrosis, and COVID-19: primarily anti-inflammatory, while IL-19, IL-20, IL-24, and IL-26 are linked to tissue damage, chronic inflammation, and airway remodeling. IL-22 occupies an intermediate position.

Differential requirements for CD8+ T cell memory formation. Infection models show IL-10R signaling benefits memory CD8+ T cell generation in LCMV infection but harms it in Listeria infection, with circulating vs. tissue-resident memory cells displaying distinct IL-10R dependencies.

IV. Therapeutic Strategies and Drug Development

IL-10/IL-10RA-based therapies fall into two categories: activating/supplementing the pathway for autoimmune diseases, or engineering approaches to overcome limitations for antitumor immunity.

Cancer immunotherapy. The first-in-human trial of IL-10-secreting CAR-T cells for relapsed/refractory B-ALL showed these cells protect mitochondrial integrity in the tumor microenvironment, preventing exhaustion and inducing stem-like memory. All 12 patients achieved MRD-negative complete remission, with 91% relapse-free and 100% overall survival at 6 months. IL-10 mRNA nanoparticles combined with checkpoint inhibitors achieved 43% complete tumor clearance in HCC models. A PD-1/IL-10 bifunctional fusion protein targets exhausted CD8+ T cells via cis-delivery, reactivating them.

Autoimmune disease treatment. Dekavil, an F8 antibody-IL-10 fusion targeting fibronectin, showed 59.3% ACR/EULAR response in a phase 1b RA trial. CD19-targeted IL-10/IL-15 CAR-NK cells are being tested for SLE, scleroderma, and Sjögren's syndrome. Recombinant IL-10 was also trialed for Wegener's granulomatosis.

V. TR-FRET Applications in IL-10/IL-10RA Research

TR-FRET combines FRET with time-resolved detection, using lanthanide chelates' long fluorescence to eliminate background noise. This homogeneous, wash-free assay is easily miniaturized to 384- or 1536-well plates. IL-10/IL-10RA TR-FRET kits quantify binding activity and assess mutant receptor effects, offering key tools for mechanistic studies.

VI. Outlook

The IL-10/IL-10RA pathway, a central immune regulator, has seen breakthroughs in both basic and clinical research. TR-FRET and other high-throughput technologies enable mechanistic and drug discovery studies. Advances in targeted delivery, engineering, and combination therapies are yielding clinical benefits beyond single-target approaches. As detection methods improve, IL-10-based interventions may find broader applications.

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