Long-term bacterial infections like pneumonia may drive a type of white blood cell to transform into tumor cells. A study from Linköping University in Sweden and elsewhere explains how this can be the initial event of the chronic lymphocytic leukemia (CLL) desease.

Chronic lymphocytic leukemia (CLL)-­the most common form of leukemia in adults-­arises from a special type of white blood cells, B lymphocytes, which normally produce antibodies to combat bacteria and viruses that we are exposed to. It is not known today what events lead to this disease.

A research team headed by Anders Rosén, professor of cell biology at Linköping University, has now established for the first time that CLL produced antibodies are highly specialized to recognize certain structures on the surface of bacteria and self-proteins of the human body (e.g. autoantigens).

The findings are being published on Monday in the respected hematological journal Blood. The key point is that the CLL antibodies also bind to damaged and dying (apoptotic) cells, which indicates that the B lymphocytes that give rise to CLL may be frontline defense cells. These are thought to have the extremely important task of using their antibodies to rapidly bind to and recognize the slightest breach in damaged mucous lining or skin, inflicted by bacteria or other microorganisms.

But in long-term infections, these B lymphocytes can start to multiply excessively and rapidly. This increases the risk of chromosome damage, which in turn make them vulnerable for leukemia transformation. The study now being published contributes to our understanding of how these B lymphocytes function and why they can be transformed into tumors.

CLL afflicts 400-500 people in Sweden each year, primarily among those aged 65-70 and more often among men than women. The disease has a highly varied course, with many patients living for decades with hardly any treatment, while others die within a few years despite treatment.

The research team behind the study also includes the doctoral students Eva Hellqvist and Anna Lanemo-Myrhinder, Linköping University, and Sohvi Hörkkö, Oulu, Finland, and Richard Rosenquist, Uppsala, Sweden.

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