DHCR7 and infection: Among the genes which were downregulated upon P. aeruginosa infection (Supplemental Table 2), 7-dehydrocholesterol reductase (Dhcr7) was decreased 7.2-fold upon infection in WT mice (p < 0.05) but only 3.2-fold in CF mice (p > 0.05); the gene stearoyl-CoA desaturase 2 (Scd2) was downregulated 5.6-fold upon infection in WT mice (p < 0.05) but only 3.0-fold in CF mice (p > 0.05).