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Mechanisms of beta cell death in diabetes: a minor role for CD95
1The Walter and Eliza Hall Institute of Medical Research, Post Office, Royal Melbourne Hospital, Victoria 3050 Australia. Allison@wehi.edu.au
Abstract:
Insulin-dependent diabetes mellitus is an autoimmune disease, under polygenic control, manifested only when >90% of the insulin-producing beta cells are destroyed. Although the disease is T cell mediated, the demise of the beta cell results from a number of different insults from the immune system. It has been proposed that foremost amongst these effector mechanisms is CD95 ligand-induced beta cell death. Using the nonobese diabetic lpr mouse as a model system, we have found, to the contrary, that CD95 plays only a minor role in the death of beta cells. Islet grafts from nonobese diabetic mice that carry the lpr mutation and therefore lack CD95 were protected only marginally from immune attack when grafted into diabetic mice. An explanation to reconcile these differing results is provided.
Insights
CD95 plays a minor role in the autoimmune destruction of insulin-producing beta cells in type 1 diabetes. Research using the nonobese diabetic mouse model shows limited protection when CD95 is absent.
Area of Science:
- Immunology
- Endocrinology
- Genetics
Background:
- Insulin-dependent diabetes mellitus (Type 1 Diabetes) is an autoimmune disease targeting insulin-producing beta cells.
- While T cells mediate the autoimmune attack, the specific mechanisms of beta cell destruction are complex.
- CD95 ligand-induced beta cell death has been proposed as a primary effector mechanism.
Purpose of the Study:
- To investigate the role of CD95 in beta cell death during autoimmune diabetes.
- To evaluate the protective effect of CD95 deficiency on islet grafts in a diabetic mouse model.
Main Methods:
- Utilized the nonobese diabetic (NOD) mouse model, specifically NOD mice carrying the lpr mutation (lacking functional CD95).
- Assessed the survival and immune attack on islet grafts from CD95-deficient NOD mice transplanted into diabetic NOD mice.
Main Results:
- Islet grafts from CD95-deficient NOD mice showed only marginal protection against immune attack when transplanted into diabetic recipients.
- These findings contradict the hypothesis that CD95 ligand is a major contributor to beta cell demise in this model.
Conclusions:
- CD95 plays a minor role in the autoimmune destruction of beta cells in the context of type 1 diabetes.
- Alternative or additional immune effector mechanisms are likely responsible for the majority of beta cell loss.