Published online before print September 6, 2007

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(American Journal of Pathology. 2007;171:1588-1598.)
© 2007 American Society for Investigative Pathology
DOI: 10.2353/ajpath.2007.070004

Molecular Interactions between T Cells and Fibroblast-Like Synoviocytes

Role of Membrane Tumor Necrosis Factor- on Cytokine-Activated T Cells

Chinh N. Tran^*, Steven K. Lundy^*, Peter T. White^*, Judith L. Endres^*, Christopher D. Motyl^*, Raj Gupta^*, Cailin M. Wilke^*, Eric A. Shelden, Kevin C. Chung, Andrew G. Urquhart and David A. Fox^*

From the Department of Internal Medicine, Division of Rheumatology,^* Rheumatic Disease Core Center, the Department of Surgery, Section of Plastic Surgery, and the Department of Orthopedic Surgery, University of Michigan Medical School, Ann Arbor, Michigan; and the School of Molecular Biosciences, Washington State University, Pullman, Washington

The mechanism of fibroblast-like synoviocyte (FLS) transformation into an inflammatory phenotype in rheumatoid arthritis (RA) is not fully understood. FLS interactions with invading leukocytes, particularly T cells, are thought to be a critical component of this pathological process. Resting T cells and T cells activated through the T-cell receptor have previously been shown to induce inflammatory cytokine production by FLS. More recently, a distinct population of T cells has been identified in RA synovium that phenotypically resembles cytokine-activated T (Tck) cells. Using time lapse microscopy, the interactions of resting, superantigen-activated, and cytokine-activated T cells with FLS were visualized. Rapid and robust adhesion of Tck and superantigen-activated T cells to FLS was observed that resulted in flattening of the T cells and a crawling movement on the FLS surface. Tck also readily activated FLS to produce interleukin IL-6 and IL-8 in a cell contact-dependent manner that was enhanced by exogenous IL-17. Although LFA-1 and ICAM-1 co-localized at the Tck-FLS synapse, blocking the LFA-1/ICAM-1 interaction did not substantially inhibit Tck effector function. However, antibody blocking of membrane tumor necrosis factor (TNF)- on the Tck surface did inhibit FLS cytokine production, thus illustrating a novel mechanism for involvement of TNF- in cell-cell interactions in RA synovium and for the effectiveness of TNF- blockade in the treatment of RA.