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The largest remaining carnivorous marsupial, the Tasmanian devil ( Sarcophilus harrisii), is currently under threat of extinction due to a fatal contagious cancer-devil facial tumour disease. Low major histocompatibility complex (MHC) class I diversity is believed to have contributed to the transmission of the tumour allograft through devil populations. Here, we report low MHC class II variability in this species, with DA β chain genes ( Saha-DAB1, 2 and 3) exhibiting very limited diversity and the sole α chain gene ( Saha-DAA) monomorphic. Three, six and three alleles were found at Saha-DAB1, 2 and 3, respectively, with a predominant allele found at each locus. Heterozygosity at these three loci is low in the eastern population and modestly higher in northwestern individuals. The results are indicative of a selective sweep likely due to an infectious disease resulting in the fixation of selectively favoured alleles and depletion of genetic diversity at devil class II loci. Several attempts were made to isolate the other marsupial classical class II gene family, namely, DB, resulting in only one DBB pseudogene being found. These findings further support the view that this species has a compromised capacity to respond to pathogen evolution, emerging infectious diseases and environmental changes. [ABSTRACT FROM AUTHOR]

Natural killer (NK) cell receptors belong to two unrelated, but functionally analogous gene families: the immunoglobulin superfamily, situated in the leukocyte receptor complex (LRC) and the C-type lectin superfamily, located in the natural killer complex (NKC). Here, we describe the largest NK receptor gene expansion seen to date. We identified 213 putative C-type lectin NK receptor homologs in the genome of the platypus. Many have arisen as the result of a lineage-specific expansion. Orthologs of OLR1, CD69, KLRE, CLEC12B, and CLEC16p genes were also identified. The NKC is split into at least two regions of the genome: 34 genes map to chromosome 7, two map to a small autosome, and the remainder are unanchored in the current genome assembly. No NK receptor genes from the LRC were identified. The massive C-type lectin expansion and lack of Ig-domain-containing NK receptors represents the most extreme polarization of NK receptors found to date. We have used this new data from platypus to trace the possible evolutionary history of the NK receptor clusters. [ABSTRACT FROM AUTHOR]

The Tasmanian devil ( Sarcophilus harrisii) is currently threatened by an emerging wildlife disease, devil facial tumour disease. The disease is decreasing devil numbers dramatically and may lead to the extinction of the species. At present, nothing is known about the immune genes or basic immunology of the devil. In this study, we report the construction of the first genetic library for the Tasmanian devil, a spleen cDNA library, and the isolation of full-length MHC Class I and Class II genes. We describe six unique Class II β chain sequences from at least three loci, which belong to the marsupial Class II DA gene family. We have isolated 13 unique devil Class I sequences, representing at least seven Class I loci, two of which are most likely non-classical genes. The MHC Class I sequences from the devil have little heterogeneity, indicating recent divergence. The MHC genes described here are most likely involved in antigen presentation and are an important first step for studying MHC diversity and immune response in the devil. [ABSTRACT FROM AUTHOR]