Class II MHC cDNAs in 15I5 B-congenic chickens

cDNA was obtained from the bursae of Fabricius of chickens from six B-congenic lines developed at this laboratory and studied for expression of class II B-LB genes. Following cDNA amplification, cloning and sequencing, genes were assigned to B-LB loci based on characteristic DNA sequences, amino acid relatedness to characterized genes, and level of expression. Genes from the B-LBI, B-LBII, and B-LBVI loci were differentially expressed in chickens with the B-2, B-5, B-13, B-15, or B-21 haplotypes. Chickens of all haplotypes expressed a B-LBII gene. Additional B-LB genes expressed included: B-LBI genes in the B-5 and B-19 haplotypes; a B-LBI/VI recombinant gene in the B-2 haplotype; and a B-LBVI gene in the B-13 haplotype. The B-congenic lines have demonstrable differences in resistance to Marek's disease (MD), and in responses to MD viral vaccines. This variability in disease resistance may be correlated with polymorphisms in the expressed B-LB genes, or with differential expression of genes at different loci.