Antigen-oriented T cell migration contributes to myelin peptide induced-EAE and immune tolerance

Astragalus polysaccharides promote neural stem cells-derived oligodendrogenesis through attenuating CD8+T cell infiltration in experimental autoimmune encephalomyelitis

Endogenous neural stem cells (NSCs) have the potential to generate remyelinating oligodendrocytes, which play an important role in multiple sclerosis (MS). However, the differentiation of NSCs into oligodendrocytes is insufficient, which is considered a major cause of remyelination failure. Our previous work reported that Astragalus polysaccharides (APS) had a neuroprotective effect on experimental autoimmune encephalomyelitis (EAE) mice. However, it remains unclear whether APS regulate NSCs differentiation in EAE mice. In this study, our data illustrated that APS administration could promote NSCs in the subventricular zone (SVZ) to differentiate into oligodendrocytes. Furthermore, we found that APS significantly improved neuroinflammation and inhibited CD8+T cell infiltration into SVZ of EAE mice. We also found that MOG35-55-specific CD8+T cells suppressed NSCs differentiation into oligodendrocytes by secreting IFN-γ, and APS facilitated the differentiation of NSCs into oligodendrocytes which was related to decreased IFN-γ secretion. In addition, APS treatment did not show a better effect on the NSCs-derived oligodendrogenesis after CD8+T cell depletion. This present study demonstrated that APS alleviated neuroinflammation and CD8+T cell infiltration into SVZ to induce oligodendroglial differentiation, and thus exerted neuroprotective effect. Our findings revealed that reducing the infiltration of CD8+T cells might contribute to enhancing NSCs-derived neurogenesis. And APS might be a promising drug candidate to treat MS.

Antigen clearance at the peak of the primary immune response induces experimental autoimmune encephalomyelitis

Autoimmune demyelinating diseases can be induced by an immune response against myelin peptides; however, the exact mechanism underlying the development of such diseases remains unclear. In experimental autoimmune encephalomyelitis, we found that the clearance of exogenous myelin antigen at the peak of the primary immune response is key to the pathogenesis of the disease. The generation of effector T cells requires continuous antigen stimulation, whereas redundant antigen traps and exhausts effector T cells in the periphery, which induces resistance to the disease. Moreover, insufficient antigenic stimulation fails to induce disease efficiently owing to insufficient numbers of effector T cells. When myelin antigen is entirely cleared, the number of effector T cells reaches a peak, which facilitates infiltration of more effector T cells into the central nervous system. The peripheral antigen clearance initiates the first wave of effector T cell entry into the central nervous system and induces chronic inflammation. The inflamed central nervous system recruits the second wave of effector T cells that worsen inflammation, resulting in loss of self-tolerance. These findings provide new insights into the mechanism underlying the development of autoimmune demyelinating diseases, which may potentially impact future treatments.

Secondary Lymphoid Organs in Mesenchymal Stromal Cell Therapy: More Than Just a Filter

Mesenchymal stromal cells (MSCs) have demonstrated therapeutic potential in inflammatory models of human disease. However, clinical translation has fallen short of expectations, with many trials failing to meet primary endpoints. Failure to fully understand their mechanisms of action is a key factor contributing to the lack of successful commercialisation. Indeed, it remains unclear how the long-ranging immunomodulatory effects of MSCs can be attributed to their secretome, when MSCs undergo apoptosis in the lung shortly after intravenous infusion. Their apoptotic fate suggests that efficacy is not based solely on their viable properties, but also on the immune response to dying MSCs. The secondary lymphoid organs (SLOs) orchestrate immune responses and play a key role in immune regulation. In this review, we will discuss how apoptotic cells can modify immune responses and highlight the importance of MSC-immune cell interactions in SLOs for therapeutic outcomes.