Inhibition of interleukin (IL)-17 production by IL-4: effect of IL-4R genotype. (A) Healthy control group IL-17 measured by enzyme-linked immunosorbent assay (ELISA) of culture supernatants. Comparison of Th17 conditions with or without IL-4: I/I, P = 0.0079; I/V, P = 0.0013; V/V, P = NS. Paired comparisons were performed using a two-tailed t-test. (B) Proportion of IL-17 inhibition by IL-4. Assuming 100% to be the maximal IL-17 production (measured by ELISA) in supernatants of cultures containing anti-CD3 and Th17 stimulatory conditions, the percentage change from baseline after the addition of IL-4 to cultures of peripheral blood mononuclear cells is shown. I, isoleucine; V, valine.