CD40 AND CD154 IN CELL-MEDIATED-IMMUNITY

CD40-CD154-mediated contact-dependent signals between B and T cells ar e required for the generation of thymus dependent (TD) humoral immune responses. CD40-CD 154 interactions are however also important in many other cell systems. CD40 is expressed by a large variety of cell type s other than B cells, and these include dendritic cells, follicular de ndritic cells, monocytes, macrophages, mast cells, fibroblasts, and en dothelial cells. CD40- and CD154-knockout mice and antibodies to CD40 and CD154 have helped to elucidate the role of the CD40-CD154 system i n immune responses. Recently published studies indicate that CD40-CD15 4 interactions can influence T cell priming and T cell-mediated effect or functions; they can also upregulate costimulatory molecules and act ivate macrophages, NK cells, and endothelia as well as participate in organ-specific autoimmune disease, graft rejection, and even atheroscl erosis. This review focuses on the role of the CD40-CD154 system in th e regulation of many newly discovered functions important in inflammat ion and cell-mediated immunity.