IL17A and rheumatoid arthritis: In a study by Shen and colleagues [26], Peripheral blood mononuclear cells from healthy control subjects and RA patients were stimulated with a combination of phorbol myristate acetate and ionomycin and this led to the detection of approximately 0.5% and approximately 1% IL-17+ T cells, respectively, whereas another study demonstrated the presence of 1% of IL-17-secreting T cells in healthy blood [25].