ABSTRACT
The presence of Langhans giant cells (LGCs) is one of the signatures of systemic granulomatous disorders such as tuberculosis and sarcoidosis. However, the pathophysiological mechanism leading to LGC formation, especially the contribution of the T cells abundantly found in granulomas, has not been fully elucidated. To examine the role of T cells in LGC formation, a new in vitro method for the induction of LGCs was developed by co-culturing human monocytes with autologous T cells in the presence of concanavalin A (ConA). This system required close contact between monocytes and T cells, and CD4+ T cells were more potent than CD8+ T cells in inducing LGC formation. Antibody inhibition revealed that a CD40-CD40 ligand (CD40L) interaction and IFN-γ were essential for LGC formation, and the combination of exogenous soluble CD40L (sCD40L) and IFN-γ efficiently replaced the role of T cells. Dendritic cell-specific transmembrane protein (DC-STAMP), a known fusion-related molecule in monocytes, was up-regulated during LGC formation. Moreover, knock-down of DC-STAMP by siRNA inhibited LGC formation, revealing that DC-STAMP was directly involved in LGC formation. Taken together, these results demonstrate that T cells played a pivotal role in a new in vitro LGC formation system, in which DC-STAMP was involved, and occurred via a molecular mechanism that involved CD40-CD40L interaction and IFN-γ secretion.
Subject(s)
CD40 Antigens/immunology , CD40 Ligand/immunology , Giant Cells, Langhans/immunology , Interferon-gamma/immunology , Membrane Proteins/immunology , Adaptor Proteins, Signal Transducing , Blotting, Western , CD4-Positive T-Lymphocytes/immunology , CD4-Positive T-Lymphocytes/metabolism , CD40 Antigens/genetics , CD40 Antigens/metabolism , CD40 Ligand/genetics , CD40 Ligand/metabolism , CD8-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/metabolism , Cells, Cultured , Coculture Techniques , Concanavalin A/pharmacology , Enzyme Inhibitors/pharmacology , Giant Cells, Langhans/drug effects , Giant Cells, Langhans/metabolism , Humans , Immunohistochemistry , Interferon-gamma/genetics , Interferon-gamma/metabolism , Interleukin-12/genetics , Interleukin-12/immunology , Interleukin-12/metabolism , Membrane Proteins/genetics , Membrane Proteins/metabolism , Mitogen-Activated Protein Kinases/antagonists & inhibitors , Mitogen-Activated Protein Kinases/immunology , Mitogen-Activated Protein Kinases/metabolism , Monocytes/immunology , Monocytes/metabolism , RNA Interference , Recombinant Proteins/pharmacology , Reverse Transcriptase Polymerase Chain Reaction , T-Lymphocytes/immunology , T-Lymphocytes/metabolismABSTRACT
Thalidomide is an effective drug for chronic inflammatory diseases, but the mechanism underlying its immunomodulatory action remains uncertain. Thalidomide has been reported to clinically improve chronic inflammatory granulomatous disorders. In such disorders, the granulomas consist of epithelioid cells, scattered lymphocytes and multinucleated giant cells (MNGC; Langhans-type cells). The present experimental approach permitted the reproduction of MNGC formation from peripheral blood monocytes and examination of thalidomides effect on it. MNGC can be effectively generated from monocytes cultured in the presence of interleukin-4 (IL-4) and macrophage colony-stimulating factor(M-CSF) for 14 days. Thalidomide can inhibit the formation of MNGC in a dose-dependent manner. MNGC formation was partly inhibited by the presence of neutralizing TNF-alpha antibody in the responses induced by IL-4 and M-CSF. Autocrinal TNF-alpha production and modulation of cadhelin expression to regulate cell adhesion might be involved in this inhibitory action of thalidomide. Our results support thalidomides clinical efficacy in the treatment of chronic granulomatous disorders (granulomatosis).