CCR6-Dependent Positioning of Memory B Cells Is Essential for Their Ability To Mount a Recall Response to Antigen

Chemokine-dependent localization of specific B cell subsets within the immune microarchitecture is essential to ensure successful cognate interactions. Although cognate interactions between T cells and memory B cells (Bmem) are essential for the secondary humoral immune responses, the chemokine response patterns of Bmem cells are largely unknown. In contrast to naive B cells, this study shows that Ag-specific Bmem cells have heightened expression of CCR6 and a selective chemotactic response to the CCR6 ligand, CCL20. Although CCR6 appears be nonessential for the initial clonal expansion and maintenance of Bmem, CCR6 is essential for the ability of Bmem to respond to a recall response to their cognate Ag. This dependency was deemed intrinsic by studies in CCR6-deficient mice and in bone marrow chimeric mice where CCR6 deficiency was limited to the B cell lineage. Finally, the mis-positioning of CCR6-deficient Bmem was revealed by immunohistological analysis with an altered distribution of CCR6-deficient Bmem from the marginal and perifollicular to the follicular/germinal center area.