CD4 and rheumatoid arthritis: To determine whether T cells from patients with active RA are sensitive to the anti-inflammatory effects of 1,25(OH)2D3, peripheral blood mononuclear cells (PBMC) from the blood of healthy controls and established RA patients, as well as synovial fluid (SF) mononuclear cells (SFMC) from RA patients, were stimulated with anti-CD3 in the presence or absence of 1,25(OH)2D3 for seven days and the frequency of CD4+ T cells expressing IL-17 or IFNγ measured by flow cytometry (Fig. 1A and B).