Moreover latest clinical data suggest that DC isolated from patients with active RA are less able to secrete TNF- when compared to healthy subjects perhaps indicating a failure to generate DC which can control unwanted pro-inflammatory T cell responses [55]. TLR-4 ligation as a 4 hour pulse of the TNF- treated DC with lipopolysaccharide (LPS) resulted in the restoration of IL-12 production and an enhancement of their T cell stimulatory capacity which resulted in an increased IFN- production. However, TNF- treated DC, when administeredin vivo,were shown to ameliorate disease in collagen induced arthritis, an experimental model of inflammatory joint disease. Mice receiving TNF- treated DC but not LPS matured DC had a delayed onset, and significantly reduced severity, of arthritis. Disease suppression was associated with reduced levels of collagen specific IgG2a and decreased inflammatory cell infiltration into affected joints. In summary the treatment of DC with TNF- generates an antigen presenting cell with a phenotype that can reduce the pro-inflammatory response and direct the immune system towards a disease modifying, anti-inflammatory state. == INTRODUCTION == Dendritic cells are powerful antigen presenting cells (APC) that are adept at both stimulating nave T cells and controlling the quality of subsequent immune responses. This control is determined by the subset of DC, and the type and duration of signals they receive. In the absence of external stimulation, DC reside in peripheral tissues in an immature state and express relatively low levels of MHC class II and no co-stimulatorymolecules[1]. These immature DC are essential mediators of peripheral tolerance to self and other non-hazardous foreign antigens [2]. The general FLNA view is usually that tolerance results from the presentation of MK-3697 antigens in the absence of full co-stimulation requirements to drive T cell activation. In response to contamination, DC undergoes both phenotypic and functional changes. The antigen presenting capacities of the DC are enhanced via the up-regulation of cell surface expression of co-stimulatory molecules (CD80, CD86 and CD40) and other molecules that promote DC-T cell clustering (CD54 and CD58). Activated DC also alter their profile of chemokine receptors to facilitate homing to lymphoid organs, and secrete various pro-inflammatory cytokines [3]. Many factors present as a result of tissue damage, inflammation and contamination are known to influence DC maturation. Such factors differ in the signals they provide to the DC therefore controlling their effector functions and hence the outcome of the immune response [4]. Thus, modulation of DC activation provides a potential therapeutic strategy to limit unwanted inflammatory responses. Rheumatoid arthritis (RA) is usually a chronic autoimmune disease characterized by joint inflammation and progressive cartilage and bone erosion [5]. Inflammatory cytokines, such as TNF- and IL-1 are vital mediators in the pathogenesis of RA, secreted predominantly by synovial macrophages and fibroblasts. In addition, increased levels of Th1 cytokines are involved[6,7].This knowledge of the mechanisms of pathogenesis led to the fundamental MK-3697 breakthrough of the use of anti-TNF- reagents as efficient therapy for RA [8-1]. However, this requires repeated administration thus incurring substantial costs to health care provision. Alternatively, the promotion or enhancement of an anti-inflammatory response is considered to contribute to a successful therapeutic strategy [12-14]. Collagen induced arthritis (CIA) is an experimental animal model of RA characterized by inflammatory cell infiltration and synovial hyperplasia leading to progressive bone and cartilage degradation [15]. In susceptible mouse strains inflammatory joint disease is mediated by a pro-inflammatory response directed towards type II collagen (CII) [16-18] in concert with the production of CII-specific complement fixing antibodies [19,20]. In light of the potential of DC to bias immune responses, we have studied the possibility of targeting these cells to modulate T cell responses in experimental arthritis. MK-3697 Our results presented in this MK-3697 paper build on the concept that TNF- modulation is usually efficacious, but innovatively we propose that short term TNF- administration to DC can be equally effective. == MATERIALS AND METHODOLOGY == == Animals == Specific pathogen free male DBA-1 mice aged 8-12 weeks were obtained from Harlan Olac, Bicester, UK and were conventionally housed and fedad libitum. All experiments were performed according to UK Home Office guidelines. == Generation and Culture of Bone Marrow Derived Dendritic Cells == Bone marrow (BM) derived DC were generated as previously described [21]. Briefly, BM cells were harvested from the femura and tibia of both hind legs and cultured in RPMI.