Have we just uncovered the cell behind Type 1 Diabetes?

Scientists have recently uncovered a new type of cell involved in the immune response that seems only to be present in individuals with Type 1 Diabetes.

It has been a long-held belief within the scientific community that there are only two types of lymphocytes (a small white blood cell that plays a role in the immune response) involved in our adaptive immune system (a subsystem of the overall immune system) composed of highly specialized, systemic cells and processes that eliminate pathogens or prevent their growth) these are T-cells and B-cells.

 

However, in a new study, while investigating specific B cells previously thought to potentially play a role in the auto-immune disease, they stumbled across a new cell which they did not recognise.

Patients with Type 1 diabetes were found to possess a hybrid of the B-cell and T-cell. The cells were termed ‘dual expresser’ cells as they displayed characteristics present in both B and T cells. Strangely, the genes that coded for the majority of hybrid cells B cell receptors showed a unique genetic code sequence which they deemed unusual as that region of the B cell receptor sequence is usually very diverse and changes significantly between individual cells.

This led the team to theorise that the genetic sequence and the receptors that the sequence produces may play a role in causing Type 1 Diabetes.

What exactly is going on inside people with Type 1 Diabetes?

Type 1 Diabetes is an autoimmune disease, which essentially means the body’s immune system is attacking our cells located in our pancreas. These cells produce insulin, which in turn means we cannot utilise the glucose in our bloodstream. This leads the body to break down our fat and our muscle tissue to provide a source of energy for the body and can cause severe weight loss.

Other symptoms include:

  • Feeling very thirsty
  • Tiredness
  • Frequent urination particularly at night

 So the question is, why does our immune system want to attack our insulin-producing cells?

One theory is that insulin is mistakenly presented to the T-cells by what is known as the Human leukocyte antigen (HLA) molecules on their surface. But there is a variation of this molecule called HLA-DQ8, which is believed to present the insulin to the T cells in a way that stimulates them to attack the hormone.

How does the newly discovered Hybrid cell come into this?

The theory is that the receptors of the hybrid cells may be able to bind to the HLA-DQ8 molecule and trigger an autoimmune response. Through a computational model, the team wanted to see if the hybrid receptor would attach to the HLA-DQ8 receptor and found that they would bind to each other 10,000 times more powerfully than the insulin receptor.

 

Before we get too excited, there are still some significant questions that need answering.

Mark Peakman, an immunologist at King's College London, says, ‘it's still not clear why the hybrid cells would produce a receptor that directs T cells to target insulin’. Explaining that the theory doesn’t explain how insulin enters the picture, ‘They don’t show whether T-cells are stimulated by insulin or by an insulin-producing cell first’.

Regardless of the limitation, he acknowledges what an exciting discovery the hybrid cells are. As he would never have questioned that there were more than two cells involved in the immune response.

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