“…PSMB12 (previously also named LMP2-like, LMP2/δ, PSMB9L or PSMB9B) and PSMB13 (previously also named PSMB7 or PSMB10) genes are members of the PSMB6/9/12 and PSMB7/10/13 families, respectively, found in teleost fish, and their levels of divergence from the respective other two family members suggest that they may be ancient [51,54,56,57]. The implication of these teleost genes in immune responses was not only suggested by their linkage within the Mhc region, but also by the increased expression of teleost PSMB8 , PSMB9 , PSMB10 (named PSMB7 in [162]), PSMB12 , PSMB13 , TAP2 and tapasin after immune stimulation (e.g., [162,163,164,165]). In humans, the molecules involved in the classical MHC class I peptide loading pathway show little allelic variation (e.g., [54]), but in rat allelic variations in TAP2 are found which appear to affect the peptides that can be presented by classical MHC class I [166,167,168] and a similar situation is found for TAP1, TAP2 and tapasin in chicken [169,170,171].…”