To investigate immunological parameters in koala tissues, we quantified CD4, CD8b, IL-6, IL-10, and IL-17A mRNA expression in the spleen, lung and heart tissues of a dead joey whose infection status (KoRV-A and KoRV-C positive) and tissue proviral loads were reported in our previous study [24], and the bone marrow of the adult koala (KM) with lymphoma that died during the study period. Here, CD4 is linked to lymphoma.