Unlike mammalian studies, the majority of investigations of MHC class I molecules in chicken remain limited to primary sequences and the structure of MHC class I molecule from the B21 haplotype was solved only recently [18, 19] . The chicken MHC B system is located on chicken Chromosome 16 (Chr16) and is composed of tightly linked polymorphic regions: BF (class I) and BL (class IIb) and a large family of polymorphic Ig-superfamily (IgSF) genes called BG-the latter sharing sequence similarities with mammalian MHC butyrophilin, myelin oligodendrocyte glycoprotein, and TRIM genes [20, 21] . The MHC B-F molecules are structurally and functionally similar to mammalian MHC class I molecules. The two class I genes are known as BF1 and BF2, although the BF2 gene is mainly expressed. The MHC class I (B-F) molecules present antigen peptides to the CD8 + T lymphocytes, which have a central role in the immune system. The MHC class I molecules of different haplotypes have specific peptide-binding tropisms, and B-F-associated peptide-binding motifs have been determined for several haplotypes, including B4, B12, B15, and B19 [22] . Thirteen peptides derived from the v-src gene of the Rous sarcoma virus (RSV) Prague strain were predicted to fit the peptide-binding motif of the MHC class I molecules of B12 haplotype and all 13 synthetic peptides actually bound to the BF12 class I molecule in subsequent binding tests [23] . This demonstrates that peptide-binding motifs can be used to predict the antigen peptides presented by chicken MHC class I molecules.