In type 1 diabetes (T1D), the insulin‐producing β cells are destructed by immune mechanisms. It has been hypothesized that the very first immune response in T1D onset comes from innate immune cells, which further activates the adaptive immune cells to attack the islets. Despite intensive research on characterization of islet‐infiltrating immune cells, the kinetics of different immune cells in multiple low‐dose streptozotocin (MLDSTZ)‐induced T1D mouse model is still much unclear. Therefore, we investigated the proportions of innate immune cells such as neutrophils, dendritic cells (DCs), plasmacytoid dendritic cells (pDCs), macrophages, natural killer (NK) cells, and adaptive immune cells (T and B lymphocytes) in thymi, pancreatic‐draining lymph nodes, and spleens of MLDSTZ mice on days 3, 7, 10, and 21 after the first injection of STZ by flow cytometry. The proportions of DCs and B cells were increased from day 3, while the proportions of B‐1a lymphocytes and interferon‐γ+ cells among NK cells were increased, but NK cells were decreased on day 10 in MLDSTZ‐treated mice, illustrating that the initial immune response is induced by DCs and B cells. Later, the proportions of T helper 1 and cytotoxic T cells were increased from day 7, suggesting that the innate immune cells precede adaptive immune cell response in MLDSTZ mice. Altogether, our data demonstrate a possible sequence of events regarding the involvement of DCs, pDCs, NK cells, B‐1a lymphocytes, B, and T cells at the early stage of T1D development.
Macrophages play an important role in the early development of type 1 diabetes (T1D). Based on the phenotype, macrophages can be classified into pro-inflammatory (M1) and anti-inflammatory (M2) macrophages. Despite intensive research in the field of macrophages and T1D, the kinetic response of M1/M2 ratio has not been studied in T1D. Thus, herein, we studied the M1 and M2 macrophages in the early development of T1D using the multiple low dose streptozotocin (MLDSTZ) mouse model. We determined the proportions of M1 and M2 macrophages in thymic glands, pancreatic lymph nodes and spleens on days 3, 7 and 10 after the first injection of STZ. In addition, we investigated the effect of IL-35 in vivo on the M1/M2 ratio and IL-35+ plasmacytoid dendritic cells in diabetic mice and in vitro on the sorted macrophages. Our results revealed that the M1/M2 ratio is higher in STZ-treated mice but this was lowered upon the treatment with IL-35. Furthermore, IL-35 treated mice had lower blood glucose levels and a higher proportion of IL-35+ cells among pDCs. Macrophages treated with IL-35 in vitro also had a higher proportion of M2 macrophages. Together, our data indicate that, under diabetic conditions, pro-inflammatory macrophages increased, but IL-35 treatment decreased the pro-inflammatory macrophages and increased anti-inflammatory macrophages, further suggesting that IL-35 prevents hyperglycemia by maintaining the anti-inflammatory phenotype of macrophages and other immune cells. Thus, IL-35 should be further investigated for the treatment of T1D and other autoimmune disorders.
In type 1 diabetes (T1D), the insulin producing β cells are damaged by immune attacks. It has been hypothesized that the very first response in T1D onset comes from innate immune cells, which further activates the adaptive immune cells to attack the β cells. The kinetics of the infiltration of different immune cells in the multiple low dose streptozotocin (MLDSTZ) induced T1D mouse model is still unclear. Therefore, we used flow cytometry to investigate the proportions of innate immune cells such as neutrophils, dendritic cells (DCs), plasmacytoid DCs (pDCs) and macrophages, and adaptive immune cells (T and B lymphocytes) in thymi, pancreatic draining lymph nodes (PDLNs) and spleens of MLDSTZ mice on days 3, 7, 10 and 21 after the first injection of MLDSTZ. The proportions of DCs and pDCs were increased on day 3 while the proportions of B-1a lymphocytes and neutrophils were increased on day 10 in MLDSTZ treated mice, illustrating that the initial immune response is induced by DCs and pDCs. The proportions of T helper 1, Helios+ T cells and cytotoxic T cells were increased from day 7, suggesting that the innate immune cells precede the adaptive immune cell response in MLDSTZ mice. We also found the proportions of interleukin-35 (IL-35) expressing tolerogenic antigen presenting cells (tolAPCs) were decreased in the spleens of MLDSTZ mice than in control mice on day 21. Furthermore, we found the proportions of IL-35+ tolAPCs were decreased in the peripheral blood mononuclear cells from T1D patients than from healthy controls. Altogether, our data demonstrate a possible sequence of events regarding the involvement of DCs, pDCs, B-1a lymphocytes, neutrophils, and Helios+ T-cells at the early stage of T1D development.
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