Major histocompatibility complex class IIA and IIB genes of Nile tilapia Oreochromis niloticus: Genomic structure, molecular polymorphism and expression patterns

► MHC class IIA and IIB cDNAs were isolated from tilapia Oreochromis niloticus. ► MHC class IIA and IIB mRNAs were expressed in all the tissues examined. ► Expressions of MHC IIA and IIB mRNAs were up-regulated after challenged with bacteria.