Issues

Diagram of the development of follicular dendritic cells (FDCs) and a primary B cell follicle (B) in lymphoid tissues. Development of the follicle requires a pre-FDC of mesenchymal origin that expresses tumor necrosis factor receptor I (TNFR-I) receptors (Matsumoto, M., Y.-X. Fu, H. Molina, G. Huang, J. Kim, D.A. Thomas, M.H. Nahm, and D.D. Chaplin. 1997. J. Exp. Med. 186:1997–2004) and B cells of bone marrow origin that produce lymphotoxin (LT)-α. The diagram illustrates an LT knockout mouse that lacks follicles but has pre-FDCs with TNFR-I (top left). Upon reconstitution with B cells from an LT-α–producing mouse (T cells are not needed), LT-α trimer binds TNFR-I trimer on the pre-FDC. This leads to maturation of the FDCs and the development of primary B cell follicles. Dr. Y.-J. Liu (DNAX, Palo Alto, CA) helped design this program. See related articles in this issue by Gonzalez et al., pp. 997–1007, and Fu et al., pp. 1009–1018.