RELT, a new member of the tumor necrosis factor receptor superfamily, is selectively expressed in hematopoietic tissues and activates transcription factor NF-kappa B

The members of tumor necrosis factor receptor (TNFR) superfamily have been designated as the "guardians of the immune system" due to their roles in im mune cell proliferation, differentiation, activation, and death (apoptosis) . This study reports the cloning of a new member of the TNFR superfamily, R ELT (Receptor Expressed in Lymphoid Tissues). RELT is a type I transmembran e glycoprotein with a cysteine-rich extracellular domain, possessing signif icant homology to other members of the TNFR superfamily, especially TNFRSF1 9, DR3, OX40, and LT beta receptor. The messenger RNA of RELT is especially abundant in hematologic tissues such as spleen, lymph node, and peripheral blood leukocytes as well as in leukemias and lymphomas, RELT is able to ac tivate the NF-kappaB pathway and selectively binds tumor necrosis factor re ceptor-associated factor 1. Although the soluble form of RELT fusion protei n does not inhibit the one-way mixed lymphocyte reaction, immobilized RELT is capable of costimulating T-cell proliferation in the presence of CD3 sig naling. These results define a new member of the TNFR superfamily that may be a potential regulator of immune responses. (Blood, 2001;97: 2702-2707) ( C) 2001 by The American Society of Hematology.