 Random gene expression of the whole genome is achieved via the action of AIRE and a self-digestion of the expressed molecules presented on both MHC-I and MHC-II molecules.B-cell receptors on the surface of B cells bind to intact native and undigested antigens of structural nature, rather than to a linear sequence of a peptide which has been digested into small fragments and presented by MHC molecules.Large complexes of intact antigen are presented in lymph nodes to B cells by follicular dendritic cells in the form of immune complexes.