A novel, alternative pathway of apoptosis triggered through class II major histocompatibility complex molecules.

Major histocompatibility complex class II (MHC-II) molecules, in addition to their role of presenting antigen to T lymphocytes, can serve as receptors triggering programmed cell death. MHC-II induced cell death affects activated/tumour transformed cells selectively, and it proceeds without the involvement of caspases, the major proteases of classical apoptosis. Caspase-independent programmed cell death can also be triggered, albeit less effectively, via a series of other cell surface molecules. Here, we discuss the major characteristics, physiological significance, and clinical relevance of caspase-independent apoptotic pathways with particular emphasis on the one induced by MHC-II ligation.