In addition, IL-8 release depended on ExoU PLA2 activity since both treatment of PA103 with MAFP and infection with PA103ΔUT/S142A, an exoU-deficient mutant complemented with site-directed mutated exoU in serine catalytic motif [6], significantly reduced IL-8 concentration in supernatants. This evidence concerns the gene CXCL8 and infection.