Immune Responses and B Complex Associated Resistance to Infectious Bronchitis Virus in Chickens.

Infectious bronchitis (IB) continues to be a global threat to poultry producers. The chicken major histocompatibility complex (MHC) or chicken B complex is compact, restricted to a single chromosome, and approximately 20-fold smaller than the mammalian MHC. Abundant evidence indicates that the B complex is strongly associated with resistance to various infectious agents in chickens. While an association between different B haplotypes and resistance against several bacterial and viral diseases has been established, additional work needs to be performed on the association between the B complex and resistance to IB viruses (IBV). Here, some of the available knowledge on genetic resistance to viral poultry diseases conferred by the chicken B locus is reviewed. IBV immune responses and resistance associated with differing B haplotype chicken lines are reviewed and discussed herein.