Killing of Human β-Cells by CD8+ T Cells Triggers Inflammatory Paracrine Signaling and Neighboring β-Cell Dysfunction

Area of Science:

• Immunology
• Endocrinology
• Cell Biology

Background:

• Type 1 diabetes involves autoimmune destruction of insulin-producing beta-cells by CD8+ T cells.
• Mechanisms of direct beta-cell killing are known, but effects on non-targeted beta-cells are unclear.

Purpose of the Study:

• To investigate the consequences of CD8+ T cell-mediated beta-cell destruction on neighboring beta-cells.
• To develop and utilize a novel in vitro model for studying bystander effects in type 1 diabetes.

Main Methods:

• Development of a coculture model using HLA-A2-expressing human beta-cells as pseudoislets and CD8+ T cells specific for the INS15-24 epitope.
• Analysis of beta-cell death, identity, insulin secretion, inflammatory markers, insulin content, and protein translation.

Main Results:

• Beta-cell death strictly depends on T-cell receptor (TCR)-HLA class I interactions.
• Neighboring beta-cells avoiding direct T-cell contact showed increased inflammation, reduced insulin content, and impaired protein translation, but maintained identity and glucose-stimulated insulin secretion.
• These bystander effects were reproducible using conditioned medium from activated CD8+ T cells.

Conclusions:

• Direct cell-cell contact is essential for CD8+ T cell-mediated beta-cell killing.
• Paracrine inflammatory signaling significantly impacts non-targeted beta-cells, contributing to type 1 diabetes pathogenesis.
• The developed pseudoislet model is a valuable platform for dissecting disease mechanisms and testing beta-cell preserving therapies.