Synoviocyte-Mediated Expansion of Inflammatory T Cells in Rheumatoid Synovitis Is Dependent on CD47-Thrombospondin 1 Interaction

• Published in: The Journal of immunology (1950) 2003-08, Vol.171 (4), p.1732-1740
• Main Authors: Vallejo, Abbe N, Yang, Hongyu, Klimiuk, Piotr A, Weyand, Cornelia M, Goronzy, Jorg J
• Format: Article
• Language: English
• Subjects: Adjuvants, Immunologic - biosynthesis; Adjuvants, Immunologic - physiology; Antigens, CD - metabolism; Antigens, CD - physiology; Apoferritins; Arthritis, Rheumatoid - immunology; Arthritis, Rheumatoid - pathology; Carrier Proteins - metabolism; Carrier Proteins - physiology; CD47 Antigen; Cell Adhesion - genetics; Cell Adhesion - immunology; Cell Division - genetics; Cell Division - immunology; Cell Line; Clone Cells; Coculture Techniques; Ferritins - biosynthesis; Ferritins - genetics; Ferritins - physiology; Fibroblasts - immunology; Fibroblasts - metabolism; Fibroblasts - pathology; Gene Expression Regulation - immunology; Humans; Synovial Membrane - immunology; Synovial Membrane - metabolism; Synovial Membrane - pathology; Synovitis - immunology; Synovitis - pathology; T-Lymphocyte Subsets - metabolism; T-Lymphocyte Subsets - pathology; Thrombospondins - biosynthesis; Thrombospondins - metabolism; Thrombospondins - physiology
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.171.4.1732

Fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis elicit spontaneous proliferation of autologous T cells in an HLA-DR and CD47 costimulation-dependent manner. T cell costimulation through CD47 is attributed to specific interaction with thrombospondin-1 (TSP1), a CD47 ligand displayed on FLS. CD47 binding by FLS has broad biological impact that includes adhesion and the triggering of specific costimulatory signals. TSP1(+) FLS are highly adhesive to T cells and support their aggregation and growth in situ. Long-term cultures of T cells and FLS form heterotypic foci that are amenable to propagation without exogenous growth factors. T cell adhesion and aggregate formation on TSP1(+) FLS substrates are inhibited by CD47-binding peptides. In contrast, FLS from arthroscopy controls lack adhesive or T cell growth-promoting activities. CD47 stimulation transduces a costimulatory signal different from that of CD28, producing a gene expression profile that included induction of ferritin L chain, a component of the inflammatory response. Ferritin L chain augments CD3-induced proliferation of T cells. Collectively, these results demonstrate the active role of FLS in the recruitment, activation, and expansion of T cells in a CD47-dependent manner. Because TSP1 is abundantly expressed in the rheumatoid synovium, CD47-TSP1 interaction is proposed to be a key component of an FLS/T cell regulatory circuit that perpetuates the inflammatory process in the rheumatoid joint.