English: Antigen presentation to B cells. Soluble antigens (red) are carried into the draining lymph nodes by the lymphatic fluids. Special subset of macrophages known as SSM (subcapsular sinus macrophages) uptake most of these antigens, and eventually present these to the resident B cells. SSM cells posses poor phagocytosis capabilities, and thus antigens are kept membrane-bound in their native form. Follicular dendritic cells obtain antigens either freely from the lymphatic fluid, or through antigen kidnapping from the SSM cells. A minority of the invading antigens reach the follicular conduits, unique anatomical structure that allows small antigens to flow through. B cells interact with the conduit channel walls, thus gaining access to the conduit lumen. If the naive BCR binds its cognate antigen, the antigen will be internalized and an adaptive immune response will take place.