PSMB9 and infection: During infection, at least in mammals, the proteasome beta (PSMB) subunits PSMB5, PSMB6 and PSMB7 are (partially) exchanged by PSMB8 (aka LMP7), PSMB9 (aka LMP2), PSMB10 (aka MECL1), respectively, creating an “immunoproteasome” with different protease properties, which leads to the generation of different peptides that are presented by classical MHC class I [14,161].