PSMB9 and neuroblastoma: A study comparing primary NB to healthy adrenal medulla reported that undetectable MHC class I antigen levels in NB tumors were due to compromised antigen presenting machinery involving a host of proteins (zeta, tapasin, TAP1 or TAP2, HLA class I heavy chain, β2 microglobulin, LMP2, and LMP7) [61].