| Abstract
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The major histocompatibility complex (MHC) is a chromosomal region whose gene products regulate the immune response and thus, disease resistance. Genetic variation in disease resistance among the turkey lines at the Ohio Agriculture Research and Development Center were reported previously, and therefore, in the current study, the MHC genotypes and phenotypes were examined in turkeys. The turkey MHC was found to be polymorphic, as similarly described for those of mammals and the chicken. Turkey deoxyribonucleic acid (DNA) banding patterns were identified by the Southern blot procedure and hybridization with chicken Class II and IV MHC probes. At least 4 Class II and 6 Class IV DNA banding patterns were identified in the turkey line under investigation. Evidence suggested that recombination had occurred between the turkey Class II and IV MHC genes. For instance, some turkeys shared the same Class II patterns, however the Class IV patterns were distinct. Similarly, some turkeys had identical Class IV genes, but not Class II genes. Characterization of multiple Class II and IV MHC combinations revealed at least 7 "molecular genotypes" in turkeys. Histocompatibility data from the graft-versus-host reaction, the mixed lymphocyte reaction, and skin grafting indicated that the 4 Class II DNA banding patterns were phenotypically-distinct and thus, they were named Mega-B through Mega-B, respectively. The four turkey Class II MHC genotypes remain segregating in a turkey line that was established during the current study. The Class IV phenotypes remain unclear, however, at least one of the genotypes (Mega-B) could be identified by antisera that were produced in turkeys which were rejecting the corresponding skin grafts. Therefore, analysis of turkey DNA by the Southern blot procedure and hybridization with chicken MHC probes can provide a means for typing turkeys at the MHC.
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