CCR6 expression in CD4+IL-17+ T cells. (a) In three ankylosing spondylitis (AS) patients and three healthy controls, the expression of C-C chemokine receptor type 6 (CCR6) in CD4+IL-17+ T cells derived from peripheral blood was analysed after in vitro stimulation with phorbol 12-myristate 13-acetate (PMA)/ionomycin antibodies. Percentages indicate the relative number of CCR6+ cells to the total number of CD4+IL-17+ T cells (top row of dot blot analysis). (b) Using an isotype control antibody after T-cell stimulation with PMA/ionomycin (bottom right) antibodies revealed no positive staining, confirming the specificity of CCR6 staining (bottom left). Without such T-cell stimulation, no CCR6+IL-17+ T cells were detected.