Schematic representation of CCR6 expression during human B-cell ontogeny and Ag-driven differentiation.

CCR6 surface expression is acquired when B cells reach the mature stage. Mature, naive B cells lose CCR6 after BCR triggering by Ag during both T-dependent TD and T-independent TI humoral immune responses and during plasma cell differentiation. CCR6 is re-expressed at the post-GC memory B-cell stage. Transient expression of CCR6 at each defined stage of B-cell maturation is compared with that of CXCR4, constitutively expressed from CD34⁺Lin⁻multipotent hematopoietic stem cell progenitors to terminally differentiated Ig-secreting plasma cells (PC).