At first, CCR4 had been shown to mark skin-homing T cells [50], expression of which has been associated with the ability of cells to traffic into peripheral tissues [51]; in addition, the percentage of CD4+/CCR4+ T cells showed significant positive correlations with the Bath Ankylosing Spondylitis Disease Activity Index in AS [52]. The gene discussed is CD4; the disease is ankylosing spondylitis.