FIGURE 1.

Stromal cell elements in the lymph node under lymphotoxin control during homeostasis and inflammation. The LT pathway is critical for the proper maintenance and function of various stromal cell elements in the LN. During homeostasis, chemokine production by FDC in the primary follicle is required for B cell positioning (1). LTβR signaling in endothelial cells of HEV is also required for the expression of sulfotransferases that promote the proper glycosylation of PNAd (2). During inflammation, the LN becomes enlarged, stromal cells acquire new functions, and increased vascularization occurs (not depicted). In addition, clusters of B and T cells aggregate within germinal centers during T-dependent immune responses, and highly differentiated FDC within the GC environment require LTβR signaling (3). To facilitate the output of plasma cells that emerge from these GC reactions, remodeling of the medullary region has been shown to occur (4).