The causes of type 1 diabetes, also known as juvenile diabetes, are not yet certain. It is known to be an autoimmune disease, linked to the destruction of the beta cells that produce insulin in the pancreas by the patient’s immune system. And that it is a multifactorial disorder, which requires a genetic predisposition, but also triggers from the environment. What this environmental signal is that can cause the onset of type 1 diabetes, however, is not certain, and a new study from Cardiff University, published in Journal of Clinical Investigationindicates a new possibility: that the onset of the disease is caused by common bacterial infections, which in some people push T lymphocytes known as “natural killers” to mistake the pancreatic cells for external invaders, and therefore eliminate them.
“Type 1 diabetes is an autoimmune disease that usually affects children or young adults, in which the cells that produce insulin are attacked by the patient’s immune system,” explains Andrew Sewell, an immunologist at Cardiff University who coordinated the new studio. “This in turn causes an insulin deficiency, which forces people with type 1 diabetes to depend on insulin injections multiple times a day to keep their blood glucose levels under control.”
The bacterium that causes diabetes
The cells responsible for the destruction of beta cells in patients with type 1 diabetes are natural killer T lymphocytes, specialized cells of the immune system that have the task of destroying other cells considered dangerous, such as tumor cells, or those infected by pathogens. In their experiments, the English researchers inserted membrane proteins present on bacteria that infect our species, such as Klebsiella oxytocaand then observed how this affected the behavior of the T cells.
“We found that after encountering proteins from certain pathogenic bacteria, T cells can actually begin to mistakenly kill the cells that produce insulin,” Sewell continues. “We also discovered T cells with this same type of cross-reactivity in the blood of patients with type 1 diabetes. This suggests that what we saw in our laboratory experiments could be the mechanism that triggers the disease.”
The cross reactivity that the scientist talks about is the phenomenon whereby sometimes the mechanisms that allow our immune system to recognize intruders can also be activated by other cells, in particular in this case the beta cells of the pancreas. The hypothesis is that some people have proteins on their membranes that are similar to bacterial ones (probably a type of protein called human leukocyte antigen, which plays a role in recognizing the body’s own cells from foreign ones), and that in This group, which makes up less than 3 per cent of the population in the UK, infection by certain bacteria can trigger the autoimmune response which gives rise to type 1 diabetes.
The hypothesis is yet to be confirmed, and even if it is, these bacterial infections could represent only one of the environmental triggers of the pathology. In any case, this is an important discovery, likely to improve understanding of the genesis of type 1 diabetes, as well as treatment and diagnosis strategies.