Although koala retrovirus (KoRV) is widely termed a pathogen, direct evidence for causation of disease impacts in koalas (Phascolarctos cinereus) remains elusive. Examination of the immune system of koalas could provide a sharper tool to investigate this but progress has been slow due to a paucity of immunological reagents in this species, and historical contradictions in research findings in this area. Our work using cross reactive antibodies to examine behaviour of resting and stimulated koala T cells (anti-human CD3); B cells (anti-human CD79b); MHCII (anti-human HLA-DP, DQ, DR) and interferon gamma (anti-bovine IFNg) by flow cytometry have revealed some features consistent with a skew to a Th2 (B cell) immune focus. Assessing the role of KoRV in immunomodulation in koalas clearly requires more in-depth research. We have used recent advances in genomics of other marsupials to develop tools necessary to assess KoRV’s effects on koala immune function in free-ranging, captive and in-vitro systems.