Recent studies from the Badovinac laboratory have shown that infection of outbred SW mice with either Listeria monocytogenes (LM) or Armstrong strain of lymphocytic choriomeningitis virus (LCMV) results in large animal-to-animal variations in pathogen-specific CD8 T cell responses when compared with their inbred C57BL/6 counterparts. The gene discussed is CD8A; the disease is infection.