Although the major histocompatibility complex of chickens (encoded in the B complex) has been studied for a number of years, almost all work has focused on the White Leghorn breed. Broiler (meat-type) chickens were derived from other breeds, including Cornish and Plymouth Rock. It was our hypothesis that new B haplotypes, not previously identified in White Leghorns, might be present in lines of broiler chickens. Furthermore, alloantisera used to identify B serotypes in Leghorn lines reportedly do not work well outside the line in which they were raised, with the result that broiler B haplotypes have not been incorporated into the universal nomenclature system. Our approach was to use a panel of B alloantisera produced to identify B serotypes within a commercial broiler breeder line (designated line A). B homozygotes identified serologically were compared by B-G genotyping using restriction fragment length polymorphism analysis. Furthermore, reverse transcription-polymerase chain reaction was used to amplify variable domains of expressed B-LB and B-F genes of homozygotes of most of the B serotypes in Line A, followed by cloning and nucleotide sequence determination. Comparison of B-LB and B-F sequences with standard Leghorn haplotypes demonstrated the existence of new alleles of B-L and B-F in a broiler breeder line, as well as the presence of alleles previously identified in Leghorns. In some cases, Leghorn-type alleles were in linkage with different B-G alleles in the broiler line than the common haplotypic associations found in Leghorn lines.

Monoclonal antibodies (MAbs) were produced against the avian reovirus strain S1133. MAbs were isotyped and used to develop diagnostic tests. Splenocytes from immunized mice were screened by enzyme-linked immunosorbent assay (ELISA). Two hybridomas secreted MAbs against avian reovirus S1133. One MAb secreted IgG1 and the other secreted IgG2a. All MAb light chains were kappa Specificity of MAbs was tested against four avian reovirus strains: S1133, 1733, CO8, and 2408. Strains S1133, 1733, and 2408 viruses were in the same subtype; the CO8 virus belonged to a different subtype. The MAbs reacted with all reovirus strains by ELISA, dot blot, immunofluorescence assay, and immunoblotting. No MAb had neutralizing activity against the tested reoviruses. Immunoblot analysis showed the one MAb bound to protein sigma A with molecular weight of 39,000 Daltons for all reovirus strains. Another MAb bound to the protein sigma C with an approximate molecular mass of 32,000 Daltons. An indirect immunoperoxidase (IP) procedure was developed using a MAb to detect reovirus in formalin-fixed, paraffin-embedded tissues from infected chickens and chicken embryo fibroblast cell cultures. The IP test was simple, fast, and economical and enabled simultaneous evaluation of viral antigen-producing cells with tissue pathologic changes confirming that the reovirus caused the lesions.

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