Major histocompatibility complex as an antigen pump: self-declaration in somatic cell society

Self-recognition by the immune system is a basic mechanism of vertebrates. Mechanisms of antigen presentation by somatic cells are based on the coupling of small peptides produced in cytoplasm and major histocompatibility complex major histocompatibility complex. The antigen pumps, including major histocompatibility complex, can present various internal molecules which are possible targets of autoimmunity, using a peptide binding mechanism. The antigen pump can transfer external signals by autoantibody and cellular immunity without a specific receptor system. This self-declaration mechanism continuously presents 'self' rather than 'non-self'. It is qualitatively impossible to differentiate self antigens from non-self antigens in this process at all. Somatic cell society is non-self for germ line DNA, since germ line DNA is symbiotic with somatic cell society. Consequently, non-self can be recognized through self-declaration.