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New research published in the Journal of Immunology could explain the link between a tick bite and inflammation associated with Lyme arthritis.

More than 300,000 American contract Lyme disease each year. This infectious disease is caused by Borrelia burgdorferi, a bacterium transferred during a tick bite.

Lyme disease is typically treated successfully with a 2-3 week course of antibiotics. However, in a small percentage of patents, symptoms, including arthritis, persist despite antibiotic treatment.

Scientists at the University of Utah Health identified a receptor on T cells that bind with molecules on the surface of B. burgdorferi. This prompts the T cell to produce inflammatory molecules, contributing to inflammation and arthritis.

This process can occur long after the initial tick bite, resulting in a  cascading cycle of inflammation.

This discovery was made thanks to research in a new model of laboratory mice that lack an anti-inflammatory molecule (IL-10) and mimic the symptoms of arthritis in people.

The mice were monitored in the 18 weeks following infection with Lyme disease. Within two weeks, there was an influx of T cells and inflammation markers in their joint fluid, despite extremely low or even undetectable amounts of B. burgdorferi. Additionally, microscopic examination of the joint tissue revealed in thickened tissue around the tendon sheath, caused by the infiltration of cells producing inflammatory molecules.

More research is needed, but early findings suggest that a focus on anti-inflammatory mechanisms may help patients with persistent Lyme arthritis.

"These findings suggest new targets for reducing the symptoms of chronic Lyme disease, those related to bystander T cell activation.  This could lead to new treatments for patients who have persistent symptoms of B. burgdorferi infection following antibiotic treatment," Janis Weis, Ph.D., professor of Pathology at the University of Utah Health, said to ALN.

"This mouse model could be used to test treatments targeting bystander activated T cells, and provide information regarding possible usefulness in patients."

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