CCR9 and infection: Only five genes were up-regulated after infection with the AA43 and AA44 CF-adapted variants in respect to AA2 infection, while the majority (15 out of 20) were down-regulated, including several chemokines and cytokines and their receptors (TNF-α, Gro-β and γ, IP-10, IL-8, FPR2, CCR6, CCR7, CCR9), and adhesion molecules involved in the process of leukocytes extravasation and recruitment (VCAM-1 and ICAM-1).