CD27 CD70 INTERACTION CONTRIBUTES TO THE ACTIVATION AND THE FUNCTION OF HUMAN AUTOREACTIVE CD27(+) REGULATORY T-CELLS/

CD27, a tumor necrosis factor receptor family member, is a costimulato ry molecule for T and B cell activation. We demonstrate here that CD27 signaling is critical for T cell activation in the autologous mixed l ymphocyte reaction (aMLR) and for aMLR-induced generation of regulator y T cells that suppress pokeweed mitogen-driven immunoglobulin G synth esis by B cells. Moreover, CD27, expressed on CD45RA(+) CD4(+) T cells , is directly involved in the suppressor function of aMLR-activated CD 4(+) T cells, probably by interfering with the interaction between CD7 0, the CD27 ligand, expressed on CD45RO(+) CD4(+) helper T cells, and CD27, expressed on B cells. CD8(+) T cells, which are required in this system to obtain suppression, on the other hand, do not need CD27 eng agement to exert their suppressor function. (C) 1997 Academic Press.