Molecular evidence for five distinct MHC class II alpha genes in the rabbit

Human HLA class II gene probes were used to identify five distinct genes encoding the class II heavy chain (alpha chain) in the rabbit. The rabbit genes were defined by both mapping data and hybridization studies of genomic clones derived from the inbred B/J rabbit strain. Analysis of the clones by hybridization at graded stringencies indicated that one group of clones corresponded to HLA-DR, one group to HLA-DQ, and two groups to HLA-DP. Clones within a fifth group, designated DN, hybridized weakly to HLA-DR and may carry a fourth species of class II alpha genes in the rabbit. Clones within the group showing high homology to HLA-DR alpha were found to also contain sequences hybridizing with a probe for HLA-DR beta. No HLA-DP, -DQ, or -DR beta sequences were detected in any of the other class II alpha clones. Distinct banding patterns observed in Southern blot analyses using either human or rabbit class II alpha probes revealed restriction fragment length polymorphism for the different rabbit haplotypes studied. The DN, DQ, and DR alpha genes appear to be present as single copies whereas there are two distinct DP-like genes in the rabbit.