A research team led by the La Jolla Institute for Allergy & Immunology and Albany Medical College has illuminated the important role of natural killer (NK) T cells in Lyme disease, demonstrating that the once little understood white blood cells are central to clearing the bacterial infection and reducing the intensity and duration of arthritis associated with Lyme disease.
"Our findings are that the NK T cells are critical to preventing the chronic inflammatory infection that causes Lyme arthritis and they participate in clearing the bacteria which cause it," said Mitchell Kronenberg, Ph.D., the La Jolla Institute's president & scientific director and co-senior author on the study, which used a mouse model of Lyme disease. Lyme disease is caused by Borrelia burgdorferi, a bacterium transmitted to humans by the bite of infected deer ticks. Typical symptoms include fever, headache, fatigue, and sometimes skin rashes. If left untreated, it can spread to the joints, the heart and the nervous system, and it can lead to serious health problems. Lyme disease currently is the most common vector (insect)-borne disease in the United States.
"What this study demonstrates is that NK T cells are an important part of our defense against Lyme disease," said Timothy J. Sellati, Ph.D., an associate professor at Albany Medical College and co-senior author on the study. "This offers the possibility that we can exploit that knowledge therapeutically and potentially develop immunological agents that can trigger more NK T cells to aide in fighting this disease." Sellati added that "NK T cells alone cannot clear Lyme disease, but are a key part of a collective immune defense."
The study's findings are outlined in a paper, "NKT cells prevent chronic joint inflammation after infection with Borrelia burgdorferi," published this week in the online version of the journal Proceedings of the National Academy of Sciences .
In an earlier study published in Nature Immunology , Kronenberg, Sellati and co-workers had shown that a glycolipid, a type of fat, found in the membrane of Borrelia burgdorferi triggered an immune response from the NK T cells. "We had found that if you gave that lipid to mice or humans, it would activate NK T cells," Kronenberg said. While this suggested the cells might play a significant role in Lyme disease, "we were missing in vivo (in the body) evidence showing that the NK T cells were activated following infection and were important for killing and clearing the Lyme disease bacteria," he said, noting that the latest study demonstrates this in an animal model.
Sellati said the finding is particularly important because it opens new lines of investigation as to the causes of chronic Lyme disease. "That's what's so exciting when you identify a new cell type as playing a central role in preventing the disease process," he said. "So in those individuals who have a more severe form of the disease, you can study their NK T cells and see if there's some deficiency that prevents those NK T cells from killing and clearing the bacteria."