An IgD-Fc-Ig fusion protein restrains the activation of T and B cells by inhibiting IgD-IgDR-Lck signaling in rheumatoid arthritis

• Published in: Acta pharmacologica Sinica Vol. 43; no. 2; pp. 387 - 400
• Main Authors: Hu, Xiao-xi, Zhang, Ai-jun, Pan, Wen-wen, Xin, Qian-ling, Chen, Jing-yu, Zhang, Ling-ling, Chang, Yan, Wu, Yu-jing, Wei, Wei
• Format: Journal Article
• Language: English
• Published: Singapore Springer Singapore 01.02.2022; Nature Publishing Group
• Subjects: 1-Phosphatidylinositol 3-kinase; Animals; Arthritis, Rheumatoid - drug therapy; Autoimmune diseases; B-Lymphocytes - drug effects; Biomedical and Life Sciences; Biomedicine; CD19 antigen; CD4 antigen; CD40 antigen; CD40L protein; CD86 antigen; Cell activation; Cell proliferation; Coculture Techniques; Collagen; Fc receptors; Flow Cytometry; Fusion protein; Humans; Immunoglobulin D; Immunoglobulin D - metabolism; Immunoglobulin D - therapeutic use; Immunoglobulin G; Immunology; Internal Medicine; Joint diseases; Lck protein; Leukocytes (mononuclear); Lymphocyte Activation - drug effects; Lymphocyte Specific Protein Tyrosine Kinase p56(lck) - metabolism; Lymphocytes; Lymphocytes B; Lymphocytes T; Male; Medical Microbiology; Mice; Mice, Inbred DBA; Microscopy, Confocal; NF-κB protein; Nuclear transport; Patients; Peripheral blood mononuclear cells; Pharmacology/Toxicology; Proteins; Receptors, Fc - therapeutic use; Recombinant Proteins; Rheumatoid arthritis; Signal transduction; Signal Transduction - drug effects; T-Lymphocytes - drug effects; Vaccine; IgD-Fc-Ig; CD4; immunoglobulin D receptor; CD19; B cells; T cells; rheumatoid arthritis; immunoglobulin D; CD4+ T cells; CD19+ B cells
• DOI: 10.1038/s41401-021-00665-w
• ISSN: 1671-4083; 1745-7254

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease characterized by synovitis and the destruction of small joints. Emerging evidence shows that immunoglobulin D (IgD) stimulation induces T-cell activation, which may contribute to diseases pathogenesis in RA. In this study, we investigated the downstream signaling pathways by which IgD activated T cells as well as the possible role of IgD in the T–B interaction. Peripheral blood mononuclear cells were isolated from peripheral blood of healthy controls and RA patients. We demonstrated that IgD activated T cells through IgD receptor (IgDR)-lymphocyte-specific protein tyrosine kinase (Lck)-zeta-associated protein 70 (ZAP70)/phosphatidylinositol 3-kinase (PI3K)/nuclear factor kappa-B (NF-κB) signaling pathways; IgD-induced CD4 + T cells promoted the proliferation of CD19 + B cells in RA patients. A novel fusion protein IgD-Fc-Ig (composed of human IgD-Fc domain and IgG 1 Fc domain, which specifically blocked the IgD–IgDR binding) inhibited the coexpression of IgDR and phosphorylated Lck (p-Lck) and the expression levels of p-Lck, p-ZAP70, p-PI3K on CD4 + T cells, and decreased NF-κB nuclear translocation in Jurkat cells. Meanwhile, IgD-Fc-Ig downregulated the expression levels of CD40L on CD4 + T cells as well as CD40, CD86 on CD19 + B cells in RA patients and healthy controls. It also decreased the expression levels of CD40L on CD4 + T cells and CD40 on CD19 + B cells from spleens of collagen-induced arthritis (CIA) mice and reduced IL-17A level in mouse serum. Moreover, administration of IgD-Fc-Ig (1.625–13 mg/kg, iv, twice a week for 4 weeks) in CIA mice dose-dependently decreased the protein expression levels of CD40, CD40L, and IgD in spleens. IgD-Fc-Ig restrains T-cell activation through inhibiting IgD-IgDR-Lck-ZAP70-PI3K-NF-κB signaling, thus inhibiting B-cell activation. Our data provide experimental evidences for application of IgD-Fc-Ig as a highly selective T cell-targeting treatment for RA.