Although it was earlier speculated that the C5aR decoy molecule C5L2 could be beneficial in reducing excessive inflammation in several lung diseases, including CF (51), it was later concluded that inactivation of C5aR by cleavage mediated by proteases released from CF neutrophils was at least partly responsible for the reduced killing and clearance of P. aeruginosa in CF lungs (52). Here, C5AR2 is linked to cystic fibrosis.