Low-affinity B cells transport viral particles from the lung to the spleen to initiate antibody responses.
Bessa J., Zabel F., Link A., Jegerlehner A., Hinton HJ., Schmitz N., Bauer M., Kündig TM., Saudan P., Bachmann MF.
The lung is an important entry site for pathogens; its exposure to antigens results in systemic as well as local IgA and IgG antibodies. Here we show that intranasal administration of virus-like particles (VLPs) results in splenic B-cell responses with strong local germinal-center formation. Surprisingly, VLPs were not transported from the lung to the spleen in a free form but by B cells. The interaction between VLPs and B cells was initiated in the lung and occurred independently of complement receptor 2 and Fcγ receptors, but was dependent upon B-cell receptors. Thus, B cells passing through the lungs bind VLPs via their B-cell receptors and deliver them to local B cells within the splenic B-cell follicle. This process is fundamentally different from delivery of blood or lymph borne particulate antigens, which are transported into B cell follicles by binding to complement receptors on B cells.