A vascular-associated fibroblastic cell controls pancreatic islet immunity

Area of Science:

• Immunology
• Endocrinology
• Cell Biology

Background:

• Pancreatic beta cells possess layered immune protection, including peripheral inhibitory networks crucial for preventing type 1 diabetes.
• Failure of these peripheral networks is implicated in spontaneous type 1 diabetes and checkpoint inhibitor-induced diabetes.
• CD4 T cells initiate autoimmune diabetes, highlighting the role of major histocompatibility complex (MHC) class II-expressing cells.

Purpose of the Study:

• To identify and characterize cells within or near pancreatic islets that may contribute to immune tolerance.
• To investigate the function of newly identified vascular-associated fibroblasts (VAFs) in presenting islet antigens and modulating T cell responses.

Main Methods:

• Detection and characterization of specific cell populations in non-diabetic mouse and human pancreatic islets.
• Functional assays assessing antigen presentation by primary VAFs to CD4 T cells.
• Evaluation of VAFs' capacity to induce T cell anergy or other regulatory responses.

Main Results:

• Vascular-associated fibroblasts (VAFs) were identified adjacent to pancreatic islets, near post-capillary venules.
• Primary VAFs spontaneously presented islet antigens to CD4 T cells and expressed inhibitory B7 receptors without costimulatory molecules.
• VAFs induced anergy in pre-activated anti-islet CD4 T cells.

Conclusions:

• Vascular-associated fibroblasts (VAFs) represent a novel cell type involved in the immune regulation of the endocrine pancreas.
• VAFs possess tolerogenic properties, including antigen presentation and induction of T cell anergy, suggesting a protective role against autoimmunity.
• These findings implicate VAFs as key players in maintaining immune privilege within the pancreatic islets and preventing type 1 diabetes.