Complement-fixing islet cell antibodies in the spontaneously diabetic BB rat

Area of Science:

• Immunology
• Endocrinology
• Diabetology

Background:

• Spontaneously diabetic BB rats are a model for Type 1 diabetes.
• Autoimmunity is implicated in the pathogenesis of Type 1 diabetes.

Purpose of the Study:

• To investigate the presence and timing of complement-fixing antibodies against islet cell surface antigens (CFA) in BB rats.
• To determine if CFA precedes the onset of overt diabetes.

Main Methods:

• Sera from BB rats were collected sequentially and assayed for CFA using radiolabeled islet cells and complement.
• Cytolytic activity was measured by the release of labeled cellular proteins.
• Control sera from normal Wistar and non-diabetic BB rats were used for basal activity assessment.

Main Results:

• Thirteen of fourteen BB rats developed strongly positive CFA.
• The appearance of CFA preceded the onset of overt diabetes in BB rats, with some appearing 4-8 weeks prior.
• Control sera showed minimal cytolytic activity (mean 7.7 +/- 1.7%).

Conclusions:

• Complement-fixing antibodies against islet cells are present before the clinical manifestation of diabetes in BB rats.
• These findings suggest that CFA may contribute to the autoimmune destruction of pancreatic islets, potentially initiating or exacerbating the disease process.