Flow cytometric enumeration of Th17 cells following a 5-day culture of peripheral blood mononuclear cells (PBMCs). (A) Representative flow cytometry histograms showing control PBMCs stained for CD4 and interleukin (IL)-17A after stimulation with anti-CD3, anti-CD3 and Th17 stimulatory conditions and anti-CD3 and Th17 stimulatory conditions with IL4. Numbers in quadrants represent the percentage of total cells expressing IL-17A. (B) Th17 and Th17/Th1 cell numbers generated in RA patient and control cultures. The difference between each cell type was statistically significant, P < 0.05, comparing the patient and control groups. I, isoleucine; V, valine.