Fig. 3.

Vasculopathic change in Juvenile dermatomyositis (JDM). The deposition of anti-endothelial cell antibodies (AECA) and C5b-9 complement complex cause endothelial damage and subsequent vasculopathy. The co-expression of MxA and VCAM-1 on muscle endothelial cells suggest the activation of the IFN1 pathway. The CXCR3, VCAM-1 and ICAM-1 expression in muscle endothelial cells reflects the endothelial cell activation, facilitating the attraction and invasion of immune cells into the muscle. CD4⁺ T cells, CD8⁺ T cells, B cells, Th17 cells, mature plasmacytoid dendritic cells (pDC) and monocytes infiltrate into the muscle compartments and form lymphoid like structures. The pDC is the major source of IFN1, which explains the IFN1 signature in biopsied muscle in JDM. Typical IFN-inducible chemokines, such as CXCL10 (IP-10) and CXCL11, are secreted by muscle endothelial cells. Cytokines related to the IFN1 signature, including Eotaxin, MCP-1, CXCL10, CXCL11, IL-10, galectin-9 and neopterin, are increased on the vascular side. T, T cells; B, B cells; Th17, T helper 17 cell.