Detection of an active complement system in red-tailed phascogales (Phascogale calura)

Very few assays that are used to assess the status of mammalian immunity have proved useful for assessment of marsupial health and/or diagnosis of disease. This is largely due to the lack of species cross-reactive reagents that underpin such experiments. To begin to address this deficit, we describe the activation of classical and alternative complement pathways of red-tailed phascogales (RTP; Phascogale calura). Using standard haemolytic assays, the existence of both complement pathways were established in RTP serum based on its ability to lyse unsensitised rabbit erythrocytes (RbE) and sensitised sheep erythrocytes (SE), respectively. The alternative complement pathway assays were conducted using pooled serum of male and female RTPs, and the remaining RTP sera were opportunistically used to test the presence of a functional classical complement system in individual animals, a first in non-eutherian animals. Observations from this study suggest that the activation of these two complement pathways in RTPs are comparable to that seen in other mammals. Since this assay was able to be used on very small samples of blood, it could serve as a useful tool to gather data for comparative immunological studies and to further our knowledge of the mechanisms of immunity available to marsupial young.