FIGURE 1.

Expression and interaction of TNFSF and TNFRSF members. TNFRSF members (depicted in blue on the right) contain variable numbers of cysteine-rich domains (CRD) in their ligand-binding extracellular regions. TNFSF ligands (left side shown in green) are active primarily as non-covalently associated homotrimers or homodimers to facilitate the formation of TNFRSF trimer clustering and its downstream signaling activation. TNFRSF members regulate the immune system mainly through either stimulating cell proliferation and maturation or promoting apoptotic cell death via a death domain. Also depicted are the primary cell types expressing TNFRSF and TNFSF, although the list is not comprehensive to represent the complex expression profile of each molecule, and some cell populations such as NK cells or monocytes are not included. Both TNFSF and TNFRSF members are widely and dynamically expressed in different immune cell populations.