Background: Regulatory T cells (Tregs) play an important role in the maintenance of immunological tolerance, so Tregs deficiency or decrease suppressor functions may be associated with development of autoimmune diseases.~Vitamin D is essential for normal bone mineralization and growth, prevention of osteopenia, osteoporosis, and nonspecific painful musculoskeletal conditions . Vitamin D is thought to have an immunomodulatory and anti-inflammatory actions, as its receptors are widely expressed in peripheral mononuclear blood cells, also its deficiency associated with several autoimmune disorders, including rheumatoid arthritis~Methods: 40 patients with active RA were randomly assigned into two groups. Group I received MTX plus hydroxychloroquine, group II received MTX and hydroxychloroquine plus vitamin D supplementation for 3 months, in addition to 30 healthy volunteers as control group. Peripheral blood Tregs were measured by Flow Cytometry.~Statistical Analysis. The collected data analyzed by SPSS software (version 16). The range, mean and standard deviation were calculated for quantitative variables. Categorical variables were expressed as number and percentages; Chi square was used as a test of their significance. Skewness, kurtosis; Shapiro-Wilk, and The Kolmogorov-Smirnov tests were used to test the normality for the data. The difference between two means was analyzed using the students (t) test (paired and unpaired samples- T tests). Significance was considered at p<0.05.
Regulatory T (Tregs) cells play an important role in the maintenance of immunological tolerance. It decrease in the peripheral blood of rheumatoid arthritis patients. Vitamin D has an immunomodulatory and anti-inflammatory effect in rheumatoid arthritis.~Vitamin D supplementation significantly enhances Tregs percentage in the peripheral blood of RA patients. So supplementation of Vit D improves rheumatoid arthritis disease activity.