Tammar wallabies receive much attention due to the need to conserve an Australian native listed as ‘extinct in the wild’. Conservation geneticists are trying to understand the evolution of their immune system, thus aiding in their regeneration.
Wallabies are born in an atricial state with an immature immune system and are highly dependant on immune factors from their mother’s milk.
A recent study has sequenced the expression of certain immunoglobin heavy and light chains, the J chain, 2 receptors - pIgR and FcRn and an IgA secreting cell called CCL28, in the mammary gland of wallabies. It was found that these immune components were differentially expressed during different phases of the lactation cycle, but mainly during two distinct periods critical in young’s’ life -birth and leaving the pouch. This is important in marsupials whose young in comparison to Eutherians, are not developed enough to absorb immunoglobins from intestines as efficiently.
Comparison with work done on the Brushtail possum showed high conservation of most of the functions of these immune components. However in the wallaby, substitutions were made in areas of genes that compromised IgA binding to its receptors.
To perform this research, cDNA libraries were prepared using RNA from lactating glands of the wallaby at specific lactating cycle days. Much like the Brushtail possum, most immunoglobins were produced during the two critical periods mentioned.
Understanding this homology within marsupials is not only helping us to understand their common ancestry but will also help their conservation.
Primary source: Daly KA, Digby M , Lefe`vre C, Mailer S, P Thomson, Nicholas K, Williamson P, 2007, Analysis of the expression of immunoglobulins throughout lactation suggests two periods of immune transfer in the tammar wallaby (Macropus eugenii), Veterinary Immunology and Immunopathology, vol 120, pp 187–200.
http://www.ncbi.nlm.nih.gov/pubmed/17727962
Interesting websites: http://learn.genetics.utah.edu/units/basics/conservation/ http://www.environment.sa.gov.au/biodiversity/tammar.html
By: Madusha Weeratunga
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