Consistent with the role of CD8 T cells in regulating EBV tumors, infection of CD8 T cell–deficient (β2 microglobulin−/−, β2m−/−) BALB/c mice reproducibly results in B cell lymphoproliferative disease or B cell lymphoma with a cumulative penetrance above 80% by 12–14 months (118). The gene discussed is CD8A; the disease is B-cell non-Hodgkin lymphoma.