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Maintaining sufficient vitamin D levels may prevent the onset of inflammatory diseases like rheumatoid arthritis, it is less effective once inflammatory disease is established because diseases such as rheumatoid arthritis leads to vitamin D insensitivity. The impact of vitamin D on inflammatory disease cannot be predicted using cells from healthy individuals or even from the blood of patients with inflammation as cells from the disease tissue are different.
If vitamin D is to be used in patients with rheumatoid arthritis, clinicians may need to prescribe much higher doses than currently provide a treatment that also corrects the vitamin D insensitivity of immune cells within the joint. Vitamin D is a potent modulator of the immune system. In particular, vitamin D can suppress inflammation in autoimmune diseases such as rheumatoid arthritis. Patients with rheumatoid arthritis are frequently vitamin D deficient and may receive vitamin D supplementation.
The study involved using paired peripheral blood and synovial fluid from the inflamed joint of patients with rheumatoid arthritis. The current understanding of vitamin D and rheumatoid arthritis is based on studies of patient blood which may not truly represent the situation at the site of inflammation -the joints. Investigating responses to the active form of vitamin D in immune cells from the inflamed joints of patients with rheumatoid arthritis compared to blood from the same patients, the inflamed joint immune cells were much less sensitive to active vitamin D.
This occurred because immune cells from the joints of rheumatoid arthritis patients are more committed to inflammation, and therefore less likely to change, even when they respond to vitamin D. Maintaining sufficient vitamin D may prevent the onset of inflammatory diseases like rheumatoid arthritis. However, for patients who already have rheumatoid arthritis, providing vitamin D might not be enough. Instead much higher doses of vitamin D may be needed, or possibly a new treatment that corrects the vitamin D insensitivity of immune cells within the joint.
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