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Reduced incidence and delayed onset of diabetes in perforin-deficient nonobese diabetic mice
1Ontario Cancer Institute, Toronto M5G2M9, Canada. dkagi@amgen.com
Abstract:
To investigate the role of T cell-mediated, perforin-dependent cytotoxicity in autoimmune diabetes, perforin-deficient mice were backcrossed with the nonobese diabetes mouse strain. It was found that the incidence of spontaneous diabetes over a 1 yr period was reduced from 77% in perforin +/+ control to 16% in perforin-deficient mice. Also, the disease onset was markedly delayed (median onset of 39.5 versus 19 wk) in the latter. Insulitis with infiltration of CD4(+) and CD8(+) T cells occurred similarly in both groups of animals. Lower incidence and delayed disease onset were also evident in perforin-deficient mice when diabetes was induced by cyclophosphamide injection. Thus, perforin-dependent cytotoxicity is a crucial effector mechanism for beta cell elimination by cytotoxic T cells in autoimmune diabetes. However, in the absence of perforin chronic inflammation of the islets can lead to diabetogenic beta cell loss by less efficient secondary effector mechanisms.
Insights
Perforin-dependent cytotoxicity is crucial for autoimmune diabetes development. Eliminating this pathway significantly reduces diabetes incidence and delays onset in mice, highlighting its role in beta cell destruction.
Area of Science:
- Immunology
- Endocrinology
- Genetics
Background:
- Autoimmune diabetes involves T cell-mediated destruction of pancreatic beta cells.
- Cytotoxic T lymphocytes (CTLs) are implicated in this beta cell elimination.
- Perforin is a key molecule mediating CTL-dependent cytotoxicity.
Purpose of the Study:
- To investigate the role of perforin-dependent cytotoxicity in the development of autoimmune diabetes.
- To determine if perforin deficiency impacts diabetes incidence and onset in a relevant mouse model.
Main Methods:
- Perforin-deficient mice were generated by backcrossing with the nonobese diabetes (NOD) mouse strain.
- Spontaneous diabetes incidence and onset were monitored over one year.
- Diabetes was also induced using cyclophosphamide injection in both wild-type and perforin-deficient mice.
Main Results:
- Perforin-deficient mice showed a significant reduction in spontaneous diabetes incidence (16% vs. 77%) compared to controls.
- Diabetes onset was markedly delayed in perforin-deficient mice (median onset 39.5 vs. 19 weeks).
- Similar insulitis and T cell infiltration (CD4+ and CD8+) were observed in both groups, suggesting perforin acts downstream of initial inflammation.
Conclusions:
- Perforin-dependent cytotoxicity is a critical effector mechanism for beta cell loss in autoimmune diabetes.
- While perforin is crucial, chronic islet inflammation can still lead to beta cell loss via alternative, less efficient mechanisms in its absence.