Scientists have discovered a genetic link that may help explain why some people with leukemia also develop autoimmune diseases.
Researchers at the Garvan Institute of Medical Research found that certain gene changes associated with blood cancer can also create abnormal immune cells that attack healthy parts of the body.
The immune system is designed to protect us from viruses, bacteria and abnormal cells. One important part of this defense is the killer T cell, a type of white blood cell that can recognize and destroy infected or damaged cells.
Normally, the body keeps these powerful immune cells under tight control. Built-in safety systems tell T cells when to grow, when to attack and when to stop, helping prevent them from damaging healthy tissue.
The new research shows what can happen when this control system breaks down. The scientists focused on changes involving STAT3, a protein that helps carry important signals inside cells and controls how immune cells grow and behave.
When STAT3 was altered, some killer T cells became unusually large and began multiplying when they should not. These cells also appeared to ignore normal signals that help keep the immune response under control.
The result was a small population of what researchers described as rogue immune cells. Instead of simply protecting the body, these abnormal T cells could attack healthy cells and contribute to autoimmune disease.
Autoimmune diseases develop when the immune system mistakenly treats the body’s own tissues as a threat. Depending on which cells or organs are attacked, this can contribute to conditions such as rheumatoid arthritis or aplastic anemia, a serious disorder in which the bone marrow does not produce enough blood cells.
Scientists have known for some time that blood cancers and autoimmune diseases can occur in the same patients. However, the biological reason for this connection has remained difficult to explain because cancer and autoimmunity can appear to involve opposite immune problems.
In cancer, abnormal cells can survive partly because they escape normal controls and avoid being eliminated. In autoimmune disease, immune cells become too aggressive and attack healthy tissue. The new findings suggest that some genetic changes may contribute to both problems.
To investigate the connection, the researchers studied blood samples from children with rare inherited autoimmune conditions. They also used CRISPR/Cas9 gene-editing technology to change STAT3 in laboratory mice and observe what happened to their immune cells.
The experiments showed that only a surprisingly small number of abnormal killer T cells may be needed to cause trouble. Rogue cells making up just 1% to 2% of the T-cell population were capable of contributing to autoimmune disease in the research models.
This finding could have important implications for diagnosis because harmful immune cells may be easy to miss when doctors examine blood using standard methods. More detailed genetic testing could eventually help identify small groups of abnormal cells before they cause extensive damage.
The research may also help doctors choose treatments more precisely. Drugs known as JAK inhibitors already target signaling pathways connected to proteins such as STAT3 and are used for some immune-related conditions, raising the possibility that genetic information could help identify patients most likely to benefit from particular treatments.
The researchers also identified two cell-receptor systems connected with stress responses, adding new clues about how abnormal immune cells communicate and survive. Further studies will be needed to determine how these discoveries can be turned into safe tests or treatments for patients.
The study was led by Dr. Etienne Masle-Farquhar at the Garvan Institute of Medical Research and was published in the scientific journal Immunity. By showing how particular genetic changes can create rogue immune cells, the research offers a clearer picture of the surprising biological connection between leukemia and autoimmune disease.
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