Trapping of naive lymphocytes triggers rapid growth and remodeling of the fibroblast network in reactive murine lymph nodes

Lymph node swelling is a hallmark of adaptive immunity. Fibroblastic reticular cells form a fairly rigid scaffold throughout lymph nodes. They not only support organ structure and compartmentalization, but also guide lymphocyte trafficking. We describe how this rigid fibroblast network reacts to acute organ swelling. Rather than being disrupted or destroyed, the fibroblast network rapidly expands by proliferation and finally covers a much larger volume to accommodate many more lymphocytes. We identified naive lymphocyte trapping by innate triggers as an early fibroblast growth signal, with activated lymphocytes playing a role only in the later growth phase.