ABSTRACT

Receptor and Ligand Interaction Members of the TN F/TNFR superfamily play multiple roles in the cellular

differentiation, survival, and death pathways that orchestrate lymphoid organo­ genesis, activation and homeostasis of immune cells.1 TNF and LTa along with LIGHT and LTß, define a core group of ligands that bind four cognate cell sur­ face receptors TNFRI, TNFRII, LTßR and HVEM with significant complexities of receptor cross-utilization (Fig. 1). Membrane-bound form of lympho toxin (LTaß) and its receptor LTßR have been studied extensively and their essential roles in the development and organization of secondary lymphoid tissues and ectopic lymphoid neogenesis were well established.2”8 LIGHT, a newly discovered TNF superfamily member (TNFSF14), is a type II transmembrane protein ex­ pressed on activated T cells and immature dendritic cells.9,10 The primary struc­ ture of human LIGHT protein predicted from the cDNA sequence contains 240 amino acids. Human LIGHT exhibits significant sequence homology with the

TNF Superfamily, edited by Sanjay Khare. © 2007 Landes Bioscience

Figure 1. A current model for the LT/LIGHT family. LTßR binds to both membrane LTaß and LIGHT while HVEM binds to LIGHT and soluble LTa3. Therefore, LIGHT binds to both LTßR and HVEM. Soluble TN Fa3 and LTa3 bind to TNFRI and TNFRII.