For the first time, scientists have found that proteins from bacteria can trigger the immune system to attack insulin-producing cells, leading to the development of type 1 diabetes.

Graphical abstract. Credit: Journal of Clinical Investigation (2024). DOI: 10.1172/JCI164535

The new research showed that killer T-cells—a type of white blood cell that's involved in tackling bacterial infections—can cause type 1 diabetes when activated by bacteria. The researchers showed that proteins from bacterial species known to infect humans could generate killer T-cells that could kill insulin-producing cells.

This research expands on their previous studies, which demonstrated that killer T-cells play a major role in initiating type 1 diabetes by killing insulin producing cells. 

Type 1 diabetes is an autoimmune disease that usually affects children and young adults, where the cells that produce insulin are attacked by the patient's own immune system. This leads to a lack of insulin, meaning that people living with type 1 diabetes need to inject insulin multiple times a day to control their blood sugar levels.

There is currently no cure for type 1 diabetes and patients require life-long treatment. People living with type 1 diabetes may also develop medical complications later in life, so there is an urgent need to understand the underlying causes of the condition to help us find better treatments.

In laboratory experiments, the researchers introduced bacterial proteins into cell lines from healthy donors and monitored the reaction of killer T-cells from these donors. They found that strong interaction with the bacterial proteins triggered killer T-cells to attack cells that make insulin.

The research, published in the Journal of Clinical Investigation, provides the first evidence of how proteins from bacterial germs can trigger the type of killer T-cells seen in patients with type 1 diabetes. The team hopes that knowing more about this process, will allow new ways to diagnose, prevent, or even halt the development of type 1 diabetes.

 Garry Dolton et al, HLA A*24:02–restricted T cell receptors cross-recognize bacterial and preproinsulin peptides in type 1 diabetes, Journal of Clinical Investigation (2024). DOI: 10.1172/JCI164535