In the current study, we identified CD4+ cells as Th cells, IL-17+∙IFN-γ− CD4+ T cells as Th17 cells, IL-17−∙IFN-γ+ CD4+ T cells as Th1 cells, and both positive IL-17+∙IFN-γ+ CD4+ T cells as “Th17∙Th1 cells.” [We do not use “Th17/Th1 cells” because the expression may be confused with the ratio of Th1 to Th17.] In the 1st group of RA patients, the ratio of Th17 cells to helper T cells (Th cells) was significantly reduced by MTX treatment (p = 0.03, Figure 1(a) left). Here, IL17A is linked to rheumatoid arthritis.