However, IL-6 −/− mice that carried the R6/2 transgene had more severe HD-associated behavioral symptoms than their IL-6 +/+ R6/2 transgenic littermates as assessed by rotarod performance (Fig. 2b and S1A), open field assay measurements (Fig. 2c-h), and rearing and climbing activity (Fig. S1B-F). This evidence concerns the gene IL6 and Huntington disease.