It appeared clearly from these models that the abnormal metabolic

It appeared clearly from these models that the abnormal metabolic control, as assessed by hyperglycaemia and glycosuria, the hallmarks of T1D clinical diagnosis, was preceded by a long phase defined as ‘prediabetes’ during which the β cell autoantigen-specific inflammatory response developed silently, yet progressively. Thus, in NOD mice

progressive infiltration of the islets of Langerhans by mononuclear cells, also termed insulitis, evolves in two distinct phases [1]. Insulitis appears by 3–4 weeks of age and up to 8–10 weeks is confined to the periphery of the islets (peri-insulitis) without any sign of active destruction of insulin-secreting β cells. As disease progresses, by 10–14 selleckchem weeks of age the infiltrating cells invade the islets quite abruptly, i.e. aggressive insulitis, and

rapid β cell destruction occurs causing overt hyperglycaemia. The orchestrated mechanisms leading to β cell destruction all represent potential targets for therapeutic intervention. These mechanisms involve a central triad constituted by β cells, autoantigen-presenting cells and T lymphocytes. Autoantigen-presenting cells are heterogeneous and include dendritic cells (DCs), selleck products macrophages and B lymphocytes. The observation that B cell-deficient NOD mice are disease free indicates that disease development is B cell-dependent [2]. In addition to their antigen-presenting role, macrophages and DCs are also key inflammatory effector cells. T lymphocytes involved in T1D are functionally heterogeneous, comprising pathogenic T cells and specialized subsets of regulatory T cells. β cell destruction involves

pathogenic T cells, as demonstrated by the capacity of ‘diabetogenic’ CD4+ and CD8+ lymphocytes from the spleen of diabetic NOD mice to transfer disease into syngeneic immune-compromised recipients [NOD neonates, irradiated adult NOD mice, NOD severe combined immunodeficiency (SCID) mice][3]. In parallel, there is evidence to show that CHIR 99021 disease progression is controlled by T cell-mediated immune regulatory circuits involving distinct subsets of regulatory T cells [4,5]. It is also important to stress that β cells must not be viewed simply as ‘passive’ targets that are killed immediately by the immune-mediated insult. In a first step they ‘suffer’ from the inflammatory environment created by the insulitis that, in a partially reversible fashion, inhibits their capacity to secrete insulin but also provides all the premises for establishing ‘cross-talk’ between the β cell and the immune cells and cytokines from the environment [6]. It is only in a second step that the β cell is eventually destroyed through apoptosis. During recent years the epidemiology of T1D has become alarming.

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