Characterisation of four major histocompatibility complex class II genes of the koala (Phascolarctos cinereus)

Major histocompatibility complex (MHC) class II molecules have an integral role in the adaptive immune response, as they bind and present antigenic peptides to T helper lymphocytes. In this study of koalas, species-specific primers were designed to amplify exon 2 of the MHC class II DA and DB genes, which contain much of the peptide-binding regions of the alpha and beta chains. A total of two DA alpha 1 domain variants and eight DA beta 1 (DAB), three DB alpha 1 and five DB beta 1 variants were amplified from 20 koalas from two free-living populations from South East Queensland and the Port Macquarie region in northern New South Wales. We detected greater variation in the beta 1 than in the alpha 1 domains as well as evidence of positive selection in DAB. The present study provides a springboard to future investigation of the role of MHC in disease susceptibility in koalas.