IL25 and cystic fibrosis: The initial reduction in IL-17F in CF aligns with the slowed bone formation during the initial phase, whereas the increase in IL-17F concentration over 2 years could indicate increases in bone formation following treatment.15 IL-17E suppresses osteoclastogenesis in rheumatoid arthritis.32 The relative increase in IL-17E concentration in CF after treatment compared to the other groups could be due to the need for continued osteogenesis and bone remodeling even after treatment is initiated.