The mechanism of capsaicin-induced apoptosis in colon cancer cells

Both the engagement of the T cell receptor with MHC-Ag complex and a second costimulatory signal are required for optimal T cell activation. Since T cells become nonreactive or tolerant without the second signal, blocking the appropriate costimulatory signal provided by APCs and T cells has been successful transplantation of allogeneic organs. We investigated the role of 4-1BB, an important costimulatory molecule for T cells, in alloimmune responses. When the 4-1BB costimulatory pathway was blocked, it led to a pronounced prolongation of allogeneic vascularized cardiac grafts. Thus, our data provide evidence that 4-1BB is required for alloimmune responses and present the possibility that blockade of the 4-1BB costimulatory pathway may be used as a therapeutic tool in preventing cardiac allograft rejection.