SUMMARYThis study was designed to investigate the therapeutic effects of interferon (IFN)-g -modulated dendritic cells (DC) in experimental autoimmune myasthenia gravis (EAMG). We induced EAMG in Lewis rats by immunization with Torpedo nicotinic acetylcholine receptor (nAChR) and adjuvant. On day 33 postimmunization (p.i.), splenic DC were prepared, exposed to IFN-g alone (IFN-g -DC) or to IFN-g in combination with 1-methyl-DL-tryptophan (1-MT), the specific inhibitor of indoleamine 2,3-dioxygenase (IDO) (IFN-g + 1-MT-DC), and injected subcutaneously into rats with incipient EAMG on day 5 p.i. A control group of EAMG rats received naive DC on day 5 p.i., while another group received 1-MT every other day, intraperitoneally (p.i.), from days 5 to 41 p.i. The severity of clinical signs of EAMG was reduced dramatically in IFN-g -DC-treated rats compared to rats receiving naive DC, IFN-g + 1-MT-DC or 1-MT alone. The number of plasma cells secreting nAChR antibodies was reduced and the expression of B cell activation factor (BAFF) on splenic and lymph node mononuclear cells (MNC) was downregulated in rats treated with IFN-g -DC. In vitro co-culture of MNC derived from EAMG rats with IFNg -DC produced relatively few cells secreting nAChR antibodies. Addition of 1-MT to the co-culture significantly increased the number of cells secreting nAChR antibodies. We conclude that IFN-g -DC reduced the number of plasma cells secreting nAChR antibodies in an IDO-dependent manner and ameliorated the development of EAMG in Lewis rats.

SUMMARYDendritic cells (DC) represent a phenotypically heterogeneous population endowed with two important biological functions, immunity and tolerance. Here we report that the injection of splenic CD8 a + DC, derived from rats with experimental allergic encephalomyelitis (EAE), delayed the onset and suppressed the severity of EAE in Lewis rats. This was accompanied by the lack of magnetic resonance imaging (MRI) lesions in the brain and spinal cord and by reduced numbers of inflammatory cells within the central nervous system. Injection of CD8a+ DC inhibited T cell proliferation that may relate to increased interferon (IFN)-g and nitric oxide production. Although CD8 + CD28-suppressor T cells, apoptotic cells and co-stimulatory molecules were not altered, CD4+ T cells expressing interleukin (IL)-10 were augmented in rats receiving CD8 a + DC compared to rats receiving total DC or medium. These results demonstrate that rat splenic CD8 a + DC could provide a cellular basis for a novel, individualized immunotherapy using autologous DC as a complement to conventional therapy in diseases with an autoimmune background such as multiple sclerosis.

Injection of myelin basic protein (MBP)-pulsed dendritic cells (DC) into healthy rats, as we reported before and observed in this study, did not induce clinical experimental allergic encephalomyelitis (EAE), but effectively protected the rats from subsequent EAE induction. The mechanisms by which MBP-pulsed DC mediate immune protection are not completely understood. In the present study, we mainly explored the dynamic change of cytokine and growth factor mRNA expression in spinal cords after subcutaneous injection of MBP-pulsed and unpulsed DC. The expression of interleukin (IL)-1, interferon-gamma and tumour necrosis factor-alpha as well as programmed death ligand (PDL)-1, PDL-2, signal transducer and activator of transcription (STAT)4, STAT6, matrix metalloproteinase (MMP)-9 and tissue inhibitor of metalloproteinases (TIMP)-2 was increased on day 0 postimmunization (p.i.). The increase of IL-12 expression was observed on day 7 p.i., while the increase of IL-10 expression mainly occurred on day 14 p.i. Except downregulation of insulin-like growth factor-1, the expression of brain-derived neurotrophic factor, ciliary neurotrophic factor, fibroblast growth factor (FGF)-2 and platelet-derived growth factor (PDGF)-B/C as well as nerve growth factor receptor (NGF-R), FGF receptor, PDGF-R-alpha and beta was elevated on day 0 p.i., while the increase of TIMP and NGF was observed on days 0 and 7 p.i. There were no significant differences on MMP-2, spinal cord-derived growth factor and PDGF-A mRNA expression. In line with the suppression of EAE induced by MBP-pulsed DC, the dynamic change of cytokines and growth factors in spinal cords should constitute a beneficial microenvironment against EAE.