Insulitis is the predominant pathological feature in

Insulitis is the predominant pathological feature in pancreatic islets of T1D subjects caused by the infiltration of autoimmune CD8+ and CD4+ T cells, CD20+ B cells, and macrophages (Campbell-Thompson et al., 2013; In\'t, 2011). TCM ryanodine trafficking in peripheral blood maintain the capacity to home to lymph nodes due to retained expression of CCR7 and CD62L molecules, which are required for migration from blood into lymph nodes across the high endothelial venules. Notably, current study revealed the modulation of CCR7 expression on CD4+ TCM, CD8+ TCM, CD4+ TEM, and CD8+ TEM cells after receiving SCE therapy in T1D subjects. These outcomes may lead to the evacuation of autoimmune cells from insulitic lesions through lymphatic vessels which express CCL19 and CCL21, the two ligands of CCR7 (Fig. 7). Additionally, the improvement of CCR7 expression on Naïve CD4+ and naïve CD8+ T cells may contribute to the redistribution and polarization of T cells and result in the restoration of homeostasis in immune system. Thus, SCE therapy delivers not only the recovery of homeostasis in pancreata, but also the comprehensive immune balance for the whole body. In comparison with conventional immune therapies (e.g., monoclonal antibodies, vaccines, Treg therapy, and dendritic cell therapy) for T1D, the ex vivo immune modulation by CB-SCs inside a device can be controlled and monitored during the treatment. The lymphocytes (including Naïve T cells, TCM, and TEM) purified by apheresis can be intensively educated by directly contact with CB-SCs, with minimum interference from red blood cells, granulocytes, and other blood components. This approach also reduces side effects associated with conventional immune therapies. Based on our combined preclinical (Zhao et al., 2007, 2009; Zhao and Mazzone, 2010) and clinical studies (Zhao et al., 2012, 2013) to date, immune modulation by CB-SCs seems to be mediated by a variety of molecular and cellular mechanisms including: 1) Expression of autoimmune regulator (AIRE) in CB-SCs plays an essential role (Zhao et al., 2012); 2) Functioning via cell–cell contact mechanisms involving the surface molecule programmed death ligand 1 (PD-L1) (Zhao et al., 2007) and CD270 on CB-SCs, and their ligands PD-1 and BTLA on variety of immune cells (e.g., T cells, B cells, monocytes, dendritic cells, and granulocytes (Li et al., 2015); 3) Acting through soluble factors released by CB-SCs (e.g., nitric oxide, TGF-β1) (Zhao et al., 2007); and 4) Adjusting the cell–cell interaction between antigen-presenting cells monocytes/macrophages and T cells through co-stimulating molecules and their ligands (Zhao et al., 2013). Thus, during the ex-vivo brief exposure to CB-SCs, T1D-derived TCM and TEM can be “educated” by the favorable microenvironment created by CB-SCs through cell to cell contact and soluble factors. Previous work demonstrated that a single treatment with SCE therapy can significantly improve fasting C-peptide levels, reduce the median glycated hemoglobin A1C (HbA1C) values, and dramatically decrease the median daily dose of insulin in Chinese patients with some residual β cell function and patients with no residual pancreatic islet β cell function (Zhao et al., 2012). Consistently, we found the regeneration of islet β cells in SCE-treated long-standing Chinese T2D subjects (Zhao et al., 2013), which express a shortage of islet β cells similar to T1D subjects. The current study demonstrated up-regulation of fasting and glucagon-stimulated C-peptide levels in Caucasian T1D subjects with some residual β cell function, including subjects with longstanding T1D. This response to SCE therapy was similar in Chinese T1D subjects, but the long-standing severe Caucasian T1D subjects with no residual pancreatic islet β cell function failed to show any increase in fasting C-peptide. To improve its clinical efficacy, it will be essential to clarify the molecular and cellular mechanisms underlying these different responses to the SCE therapy. Ongoing mechanistic studies revealed the molecular disparities of expression of muscarinic acetylcholine receptors (mAChRs) on human islet β-cell regeneration between Caucasian and Chinese populations (Figs. S3 and S4). The M2 receptor and other specific cholinergic markers such as vesicular acetylcholine transporter (vAChT) and choline acetyltransferase (ChAT) are substantially expressed on the islet β cells of the Chinese population (Fig. S3). It indicates the autocrine cholinergic signal involved in the functional regulation of islet β cells of Chinese population. However, in pancreata of Caucasian population, M3 and M5 muscarinic receptors were strongly expressed on the islet β cells (Molina et al., 2014); pancreatic islet α cells display M2 receptor and produce cholinergic signal that contributes to the modulation of islet β-cell function via the paracrine pathway (Rodriguez-Diaz et al., 2011). Additionally, animal studies have shown that parasympathetic innervation modulates the β-cell proliferation and function of pancreatic islets (Lausier et al., 2010; Rodriguez-Diaz et al., 2012), suggesting a possible mechanism for differences in response to SCE therapy based on the different receptor subtypes. The M2 receptor-mediated signaling may function as a new molecular target that contribute to the modulation of islet β-cell expansion.