Corresponding 2-color immunohistological images of liver tissue sections show a high degree of infection with only a few tissue-infiltrating CD8+ T cells, that are M45-Db CTL, after infection with mCMV-Δm04m06, whereas additional expression of m04 by mCMV-Δm06 recruits M45-Db CTL to infected cells, thereby forming nodular inflammatory foci (NIF), which are known histological correlates for viral epitope-specific protective activity [101]. The gene discussed is CD8A; the disease is infection.