Allelic diversity and tissue expression of MHC class I genes in the duck (Anas platyrhynchos)

We examined the tissue expression and the polymorphic nature of major histocompatibility complex (MHC) class I alleles expressed in the duck (Anas platyrhynchos). Cloning and sequencing of the MHC class I transcripts from six ducks showed that each individual expresses two alleles, with the majority of the polymorphic positions lying in the exons encoding the peptide binding region (PBR). Northern hybridization revealed that MHC class I expression is greatest in spleen, liver, intestine and lung, with lower expression in other tissues. Additionally, the expression of these genes varies in different individuals. In vitro infection of primary duck hepatocytes with the duck hepatitis B virus (DHBV) showed that viral replication was not associated with a down regulation of the MHC class I transcription. We also investigated whether ducks have a natural killer (NK) cell activating receptor of the Ig-like type. Homology-based approaches failed to identify duck homologues of the human NKp46 receptor and the chicken Ig-like receptors (CHIR).