Immunological profile and aspects of immunotherapy in type 1 diabetes

University dissertation from Linköping : Linköping University Electronic Press

Abstract: Type 1 diabetes (T1D) is a chronic, autoimmune disease caused by a T cell mediated attack on the insulin producing pancreatic ß-cells. Even though reasonable quality of life can be acquired with modern insulin therapy, prevention of acute and late serious complications is facilitated by preservation of residual insulin secretion. Preventing β-cell destruction is therefore an important goal of T1D therapy. Characterisation of immunological changes in the course of T1D is essential for understanding the underlying pathogenic mechanisms and for evaluating the efficacy of therapeutic intervention. This thesis aimed to study the immune profile in individuals at increased risk of T1D and in patients diagnosed with the disease. In addition, the immunological effects of treatment with the B vitamin, Nicotinamide, and by antigen-specific immunotherapy using GAD65, have been studied in high-risk individuals and in T1D patients, respectively. We have found that individuals at high risk of T1D had an increased T helper (Th) 1 like immune profile, defined by high secretion of interferon (IFN) -γ. At the time of clinical onset of T1D, the Th1 dominance was diminished. We further demonstrate that children with newly diagnosed T1D had a suppressed Th1 like profile, detected by chemokine and chemokine receptor profile. This was accompanied by an induced population of CCR7+ and CD45RA+ naïve, CD8+cytotoxic T (Tc) cells and a reduced CD45RO+ memory Tc cell pool. It has previously been shown that oral Nicotinamide had no clinical effect in prevention of T1D. However, we found that the treatment was associated with a decreased secretion of IFN-γ. We have previously shown that subcutaneous injections with GAD-alum in T1D children induced a better preservation of endogenous insulin secretion compared with placebo. Here, we demonstrate that the treatment induced an early antigen-specific Th2 and regulatory immune profile. After a few months, and still after more than two years, the recall response to GAD65 was characterised by a broader range of cytokines. GAD-alum treatment also induced a GAD65-specific CD4+CD25highFOXP3+ cell population and reduced the levels of CD4+CD25+ cells. In conclusion, a Th1 like immune profile in pre-diabetic individuals indicates an imbalance of the immune system. At time of clinical onset, and in the period afterwards, reduction of the Th1 associated immune response could be an effect of a suppressed destructive process, selective recruitment of effector T cells to the pancreas or a defective immune regulation. The protective effect of GAD-alum in T1D children seems to be mediated by an early skewing of GAD65-induced responses towards a Th2 phenotype. Further, induction of GAD65-specific T cells with regulatory characteristics might be able to suppress autoreactive responses and inflammation in the pancreas.

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