Consistent with the microarray, protein levels of GBP2 and GBP5 were reduced in the Ifnar1−/−, Irf9−/−, Irf1−/−, Trif−/−, and Irf3−/−Irf7−/− macrophages that undergo extensive cell-cell fusion during infection but not in Myd88−/− (Fig 2B). The gene discussed is IRF1; the disease is infection.