Poster Presentation Society for Molecular Biology and Evolution Conference 2016

The role of immunoglobulins in the Tasmanian Devil Facial Tumour Disease (#371)

Beata Ujvari 1 , Thomas Madsen 1 , Katherine Belov 2
  1. Centre for Integrative Ecology, Deakin University, Waurn Ponds, Vic, Australia
  2. University of Sydney, Sydney, NSW, Australia

The Tasmanian devil immune system has recently been under scrutiny because of the emergence of a contagious cancer, the Tasmanian Devil Facial Tumour Disease (DFTD), which has decimated devil numbers. In the current study therefore we investigate the role of immunoglobulins in DFTD status, by (i) providing a comprehensive description of the Tasmanian devil immunoglobulin variable regions, and by (ii) investigating how IgG and IgM expression dynamics determines DFTD prevalence. First we show that heavy chain variable (VH) and light chain variable (VL) repertoires are similar to those described in other marsupial taxa: VL diversity is high, but VH diversity is restricted and belongs only to clan III. Phylogenetic analyses revealing highly complex and ancient devil VL gene segments, with some lineages predating the separation of marsupials and eutherians. We suggest that, similar to other studied marsupial species, the complex VL segment repertoire compensates for the limited VH diversity in Tasmanian devils.

Second we show that immunoglobulin M (IgM) and G (IgG) expression levels as well as IgM/IgG ratios decrease with increasing devil age. Neither age, sex, IgM nor IgG expression levels affect devil DFTD status in our analyses. However, devils with increased IgM relative to IgG expression levels show significantly lower DFTD prevalence. Our results therefore suggest that IgM/IgG ratios may play an important role in determining devil susceptibility to DFTD. Our study further support the fact that the Tasmanian devil’s immune system is competent and that their susceptibility to Devil Facial Tumour Disease is the result of immune evasion by the tumour and not because of inadequacies in the Tasmanian devil immune system.