In these experiments, we used the atherosclerosis-prone apolipoprotein E–deficient (ApoE−/−) mouse and ApoE−/− mice crossed with CD4−/− [double-knockout (DKO)] mice to test the hypothesis that inhaled asbestos fibers exacerbate atherosclerosis and that the mechanism involves CD4+ T cells that are increased in lung after inhalation of asbestos (Shukla et al. 2007). The gene discussed is CD4; the disease is atherosclerosis.