Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 11 1 2012 03 15 1 13 EN Mohammad Hossein Karimi Transplant Research Center, Shiraz University of Medical Sciences, Shiraz, Iran Ali Akbar Pourfathollah Department of Immunology, Faculty of Basic Medical Sciences, Tarbiat Modares University, Tehran, Iran 2015 10 01 CD40 is recognized as a member of tumor necrosis factor receptor super family. It is expressed by the immune and non-immune cells. Its interaction with CD40 ligand (CD154) brings about  a regulatory effect on  the cellular and humoral immunity. The pathway of CD40-CD154 is influential in various diseases. Investigations on such diseases have revealed dimensional mechanisms whereby this route intensifies host protection. Moreover, through these mechanisms, pathogens subvert the signaling of the CD40, conditions in which the CD40–CD154  pathway promotes  disease and  also through  the  relevant modulation  for immunotherapy. This review focuses on the role of CD40–CD40L (CD154) interactions in dendritic cells (DCs) regulation, tolerogenic dendritic cells, role of CD40 in autoimmune disease, allograft rejection and induction of tolerance by down regulation of CD40. According to these roles, it is assumed that  CD40  is a functional molecule in the  pathologies of  conditions  like autoimmune diseases and allograft rejection caused by activated T and B cells. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/325 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/325/325