B cell–restricted overexpression of the costimulatory ligand CD70 instead led to increased T effector cells expressing the proatherogenic TH1 cytokine IFNγ but, unexpectedly, reduced atherosclerosis in ApoE*3-Leiden mice.77 Chronic IFNγ exposure depleted these transgenic B cells and atheroprotective oxLDL antibody titers over time; so this does not offer an explanation. The gene discussed is APOE; the disease is atherosclerosis.