CD4 and rheumatoid arthritis: Moreover, 50, 100, and 200 μg/mL oleuropein, the most common polyphenolic detected in olive leaves, showed potential to shift CD4+ T cells from peripheral blood mononuclear cells of RA patients to CD4+CD25+FoxP3 Tregs and induce the production of IL-10 and TGF-β [282].