“…The Major Histocompatibility Complex (MHC) is a cluster of genes which encodes cell-surface glycoproteins that are involved in antigen recognition in immune responses. The MHC, or the B-complex as it is called in chickens, is closely associated with individual differences in susceptibility to many poultry diseases, such as Marek's disease (Briles et al, 1982), Rous sarcoma virus (Plachy et al, 1992), fowl cholera caused by Pasteurella multocida (Lamont et al, 1987), coccidiosis (Bumstead and Millard, 1987;Caron et al, 1997) and salmonellosis (Cotter et al, 1998). Although information on the involvement of the B-complex in resistance to helminth infections is very limited, Wetherall and Groth (1992) have shown that in mice certain MHC haplotypes are associated with resistance to helminths.…”