Given the relationship between IFN-γ expression and chlamydial infection, the low levels of IFN-γ expression seen in our vaccinated koalas could possibly be explained by the low to no detectable levels of C. pecorum. Therefore, from this data, it appears that IFN-γ is not a direct marker for infection or disease and does not seem to be responsible for the resolution of infection, in these ocular diseased koalas. The gene discussed is IFNG; the disease is infection.