T cells accumulate in non-diabetic islets during ageing

Area of Science:

• Immunology
• Endocrinology
• Gerontology

Background:

• Resident immune cells in pancreatic islets influence islet function and diabetes pathology.
• Macrophages are the predominant immune cells in islets, with T cells being less studied.
• The role of non-macrophage immune cells, like T cells, in islet aging is unknown.

Purpose of the Study:

• To investigate the presence and dynamics of non-macrophage immune cells, specifically T cells, in pancreatic islets.
• To determine if T cell populations in islets change with age or diet-induced obesity.
• To compare islet immune cell populations in mice and humans.

Main Methods:

• Isolation of pancreatic islets from aging C57BL/6J male mice (3-24 months) and mice on a high-fat diet.
• Flow cytometry analysis of immune cell populations in mouse and human islets.
• Characterization of T cell subsets (αβ, γδ, CD4+, CD8+, regulatory T cells).

Main Results:

• Immune cells constitute approximately 2-3% of total islet cells in both mouse and human islets.
• T cells and B cells represent a small fraction (2-4%) of the total islet immune cell compartment in young mice.
• Islet T cell numbers increase linearly with age in mice, independently of body weight or high-fat diet.
• The majority of islet T cells are αβ T cells, including CD8+, CD4+, and regulatory T cell subsets.

Conclusions:

• T cells are a normal constituent of the pancreatic islet immune microenvironment in both mice and humans.
• Islet T cell accumulation occurs with aging in a body weight-independent manner.
• These age-associated T cells may play a role in the physiology of islet aging.