Conduits Mediate Transport of Low-Molecular-Weight Antigen to Lymph Node Follicles

Abstract

Summary Recent studies report that B cells acquire large lymph-borne antigens and immune complexes directly from subcapsular sinus macrophages while small antigens appear to diffuse directly into the B cell follicles. To directly compare entrance of large and small Ags into the follicles, we used multiphoton intravital microscopy to track drainage of Ag into the peripheral lymph nodes and subsequent encounter by B cells and follicular dendritic cells in the underlying follicles. We find that a system of conduits extends into the follicles and mediates delivery of small antigens to cognate B cells and follicular dendritic cells. The follicular conduits provide an efficient and rapid mechanism for delivery of small antigens to B cells, which directly contact the CXCL13 chemokine-enriched conduits. By contrast, large antigens were bound by subcapsular sinus macrophages and subsequently transferred to follicular B cells as previously reported.