Under these circumstances it is highly likely that presentation of autoantigen also takes place in the joint. Therefore, it could be speculated that, in RA, tolDC would ideally have the ability to act in several locations: in the rheumatoid joint to anergize autoantigen-specific effector T cells locally, and in the draining lymph node to
induce Tregs from autoantigen-specific naive T cells. However, it should be noted that T cells from RA patients can be resistant to at least some tolerogenic signals; for instance, they can resist Selleck RG7204 IL-10- and IDO-mediated suppression [90, 91]. Our tolDC operate, at least partially, via a TGF-β-dependent mechanism and inhibit proliferation and IFN-γ production of peripheral blood RA T cells in vitro (unpublished data); however, whether they can inhibit autoreactive T cells in the rheumatoid joint remains to be determined. Despite the fact that our tolDC have similar ability as mature DC to process and present exogenous antigen, tolDC have lower T cell stimulatory capacity than mature DC, in line with their lower expression of co-stimulatory molecules and low production of proinflammatory cytokines [55, 82]. Moreover, tolDC induce hyporesponsiveness (‘anergy’) in antigen-experienced memory T cells while
polarizing naive T cells towards an anti-inflammatory cytokine profile . We have also shown that, in a mouse in-vivo model Forskolin datasheet of collagen-induced arthritis, murine bone marrow-derived tolDC generated with Dex, VitD3 and LPS have a therapeutic effect: treatment see more of arthritic mice with tolDC (1 million cells injected intravenously three times over 8 days) reduced significantly the severity and progression of arthritis, whereas treatment with immunogenic mature DC did not reduce disease and, in fact, exacerbated arthritis . Interestingly, tolDC exerted a therapeutic effect only if they had been loaded with the immunizing antigen, type
II collagen. Treatment with tolDC was associated with a reduction in Th17 cells and an enhancement of IL-10-producing T cells, and a reduction in type II collagen-specific T cell proliferation, possibly explaining their therapeutic effect. Thus, this type of tolDC is a potentially powerful tool for the treatment of RA and other autoimmune diseases. Before tolDC can be applied in a clinical trial, a protocol to generate clinical grade tolDC, compliant with current good manufacturing practice (cGMP) regulations, had to be established. For this purpose, the research-grade fetal calf serum (FCS)-containing medium was replaced with cGMP-grade medium specialized for DC (CellGro® DC medium from CellGenix, Freiburg, Germany) and LPS was replaced with MPLA, a synthetic cGMP-grade TLR-4 ligand (from Avanti Polar Lipids, Alabaster, AL, USA).