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High Levels of Certain Immune Cells
Graves' disease is an autoimmune disorder which results in an overactive thyroid. Up to half of those affected by the disease will develop inflammation or fibrosis around their eyes, creating the bulging appearance associated with Graves' eye disease.
A cell type that causes significant scarring in lung disease appears to have a similar effect in Graves' disease, researchers have found. The cells, called fibrocytes, are present at a higher than normal frequency in patients with Graves' disease, according to a new study.
Fibrocytes are immune cells derived from bone marrow that circulate through the bloodstream. They can infiltrate tissue, like the lungs, kidney, and liver, generating excess connective tissue and areas of fibrosis, for example, following pulmonary or kidney injury.
To determine whether fibrocytes play a similar role in Graves' disease, the investigators examined tissue samples from 70 patients with the disease and compared them to 25 healthy subjects. They found that fibrocytes were present at substantially higher frequencies—as much as five times greater—in patients with Graves' disease. These levels were observed in both the bloodstream and in the orbital tissues of patients who had developed thyroid eye disease.
In earlier studies, the antigens that trigger the overactive immune response in Graves' disease were identified. Now the scientists report that fibrocytes express the same antigens: thyroid-stimulating hormone receptor (TSHR) and insulin-like growth factor-1 receptor (IGF-1R). In addition, the researchers say, when these receptors are activated, they produce a large quantity of cytokines which could stimulate immune cells to the orbit, causing inflammation in thyroid eye disease.
MEDICA.de; Source: University of Michigan Health System