During infection with the clone 13 strain of LCMV, NK cells aided in the development of persistent infection rather than fatal immunopathology through perforin-mediated lysis of activated CD4 T cells, a population which acts to sustain function of the virus-specific CD8 T cells that mediate virus clearance and tissue damage (Waggoner et al., 2012). The gene discussed is CD8A; the disease is infection.