Since il1b and cxcl8 expression were not affected by Mtz or solvent (DMSO) treatment in K56-2 or PBS injected wildtype embryos (S8A Fig), nor in PBS-injected macrophage-depleted mpeg1/umn+ embryos (Fig 8C and 8D), these results show that zebrafish macrophages contribute significantly to the infection-induced increase in global il1b expression. Here, MPEG1 is linked to infection.