X cell in the immune system identified which could be linked to type 1 diabetes

Jack Woodfield
Fri, 31 May 2019
X cell in the immune system identified which could be linked to type 1 diabetes
Scientists have discovered a rogue immune cell coined the X cell which may be behind the development of type 1 diabetes.

US scientists from Johns Hopkins Medicine and IBM Research say further studies are needed to confirm the discovery, but claim they have "strong evidence" it could be a driver for type 1 diabetes.

The X cell is a type of white blood cell, a "rogue hybrid" cell that can act as both a B cell and a T cell. B cells typically identify threats and produce antibodies that alert the body, whereas T cells look for cells and destroy them before they can do any harm.

One of the researchers, Dr Abdel-Rahim A. Hamad, said: "What is unique about the entity we found is that it can act as both a B cell and a T cell. This probably accentuates the autoimmune response because one lymphocyte is simultaneously performing the functions that normally require the concerted actions of two."

In type 1 diabetes, insulin-producing cells are targeted erroneously, but the mechanism behind this immune reaction is not fully understood.

Researchers hypothesise the process comprises insulin binding to a variant surface marker called DQ8, which could hypothetically lead to T cells attacking what it perceives as threatening.

"However, our experiments indicate that it is a weak binding and not likely to trigger the strong immune reaction that leads to type 1 diabetes," said Dr Hamad.

What the researchers believe they have discovered is the emergence of a second protein in the process, which is responsible for elimination of beta cells.

They used blood samples from volunteers at the Johns Hopkins Comprehensive Diabetes Center and stumbled upon the X cell. Not only is it a B cell and T cell, but also its own special kind of cell.

The B cell receptors observed were shown to code for a protein that could explain the amplified insulin reaction. This protein, called x-Id, binds to DQ8 with a thousand times the strength of insulin. This leads to an augmented leap in the T cell response, potentially revealing the moment type 1 diabetes begins.

"This finding, combined with our conclusion that the x-Id peptide primes T cells to direct the attack on insulin-producing cells, strongly supports a connection between [the X cell] and type 1 diabetes," said Dr Hamad.

Now, the researchers are planning further studies to confirm the cell's actions and hopefully provide insight into how their findings could be translated into future treatments.

The study was published in the journal Cell.
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