The identification of immune genes in the milk transcriptome of the Tasmanian devil (Sarcophilus harrisii).

Tasmanian devil (Sarcophilus harrisii) pouch young, like other marsupials, are born underdeveloped and immunologically naïve, and are unable to mount an adaptive immune response. The mother's milk provides nutrients for growth and development as well as providing passive immunity. To better understand immune response in this endangered species, we set out to characterise the genes involved in passive immunity by sequencing and annotating the transcriptome of a devil milk sample collected during mid-lactation. At mid-lactation we expect the young to have heightened immune responses, as they have emerged from the pouch, encountering new pathogens. A total of 233,660 transcripts were identified, including approximately 17,827 unique protein-coding genes and 846 immune genes. The most highly expressed transcripts were dominated by milk protein genes such as those encoding early lactation protein, late lactation proteins, α-lactalbumin, α-casein and β-casein. There were numerous highly expressed immune genes including lysozyme, whey acidic protein, ferritin and major histocompatibility complex I and II. Genes encoding immunoglobulins, antimicrobial peptides, chemokines and immune cell receptors were also identified. The array of immune genes identified in this study reflects the importance of the milk in providing immune protection to Tasmanian devil young and provides the first insight into Tasmanian devil milk.