Prophylactic Treatment with Intravenous Immunoglobulin Attenuates Experimental Optic Neuritis in Mice.

Optic neuritis is characterized by optic nerve inflammation, demyelination and axonal loss. Intravenous immunoglobulin (IVIg) has been reported to be effective for steroid-resistant patients. However, there is no report investigating the histopathological efficacy of IVIg in optic neuritis models. In this study, we examined the effects of IVIg on optic neuritis of experimental autoimmune encephalomyelitis (EAE) and experimental autoimmune optic neuritis (EAON). Inflammation, demyelination and axonal loss were assessed in the optic nerve sections. IVIg showed dose-dependent prevention of clinical symptoms in EAON. IVIg provided an anti-inflammatory effect in both EAE and EAON, associated with improved demyelination. Axonal loss in EAE was also significantly attenuated. These results suggest that IVIg has neuroprotective properties in experimental optic neuritis, and is a promising new treatment for optic neuritis.

Immunoglobulin G Enhances Generation of Inducible T Regulatory Cells and Increases Their Regulatory Function.

Intravenous immunoglobulin (IVIg) has been shown to be effective in the treatment of a variety of autoimmune diseases. To clarify the role of T regulatory cells (Tregs) in the immunoregulatory effect of IVIg, we focused on human inducible T regulatory cells (iTregs) and investigated the mechanism of action of IVIg. When immunoglobulin G (IgG) was added to a culture system that differentiates iTregs from anti-CD3 antibody activated CD4+CD25- T cells in the presence of syngeneic immature dendritic cells, interleukin (IL)-2 and transforming growth factor-ß (TGF-ß), the expression of forkhead box P3 (FoxP3), which is the master transcription factor for Tregs in CD4+CD25+ T cells, increased in an IgG concentration-dependent manner. The expression of FoxP3 in iTregs in the 20 mg/mL IgG group was twice as high as that in the saline group. iTregs that highly expressed FoxP3 not only partially suppressed the polyclonal proliferative response of T cells derived from the same individual but also produced significantly more inhibitory cytokines IL-10 and TGF-ß. The ability of IgG to enhance iTregs differentiation was also observed in the Fc fragment, but not in the F(ab')2 fragment. These results suggest the clinical regulation of immune responses by IVIg administration may contribute at least to enhancing the differentiation of iTregs and partial immunosuppressive functions.

[Enhancement of regulatory T cell induction by intravenous S-sulfonated Immunoglobulin during the treatment of experimental autoimmune encephalomyelitis].

Intravenous immunoglobulin (IVIg) has been shown to be effective for a variety of autoimmune diseases. Despite its widespread use and therapeutic success, the precise mechanisms for the anti-inflammatory therapeutic effects of IVIg are not well understood. In particular, few reports have examined the mechanism of IVIg on regulatory T cells (Treg: CD4(+)CD25(+)FoxP3(+) T cells). In the present study, to clarify the effect of intravenous S-sulfonated immunoglobulin (S-IVIg) on Treg, we investigated experimental autoimmune encephalomyelitis (EAE), the representative animal model of autoimmune disease. First, when we evaluated the effect of S-IVIg in an acute EAE model, the prophylactic treatment of S-IVIg dose-dependently controlled the symptoms of EAE. Next, we measured Treg in EAE mice spleen by flow cytometry. The percentage of Treg in S-IVIg-treated mice was significantly increased compared with Saline-treated mice. Finally, in reinduced EAE, S-IVIg not only prevented EAE progression, but also increased the percentage of Treg in the spleen. The increase in percentage of Treg in S-IVIg-treated EAE might be associated with protection against EAE. These observations provide important evidence that IVIg is effective in T-cell-mediated control of autoimmunity.