Inflammation is present in the Cystic fibrosis (CF) airway from the time of infancy, and worsens with the onset of chronic infection. Therapies with proven benefit are associated with decreased airway inflammation. Thus, sensitive and reproducible biomarkers of airway inflammation have long been sought as a necessary component to improved clinical care and to facilitate therapeutic trials for CF. FEV1, the standard outcome measure in CF, is recognized as an insensitive outcome measure. the investigators have identified a panel of 10 genes which sensitively predict resolution of pulmonary inflammation, in response to therapy of an acute pulmonary exacerbation. With the goal of yielding a technically simple but unique CF biomarker assay, the investigators have tested whether proteins signified by these genes show large changes in expression following treatment of acute pulmonary exacerbations. Protein quantifications are among the most common measurements performed in clinical laboratories around the world. Based on preliminary findings that changes in white blood cell proteins mirror changes seen in the genes, the investigators propose to identify top candidate proteins, from the investigators gene panel, which change in response to exacerbation therapy. Once identified, these proteins will be quantified directly with a new blood test which is inexpensive and simple to perform. The investigators propose to validate this blood test in a single site trial. If successful, this proposal will yield a biomarker assay that will be available to validate in a multi-site trial and provide unique insights into mechanisms that regulate white blood cell activation and recruitment in CF lung disease.

Inclusion Criteria:

1. Documented diagnosis of CF.
2. Age 18 years old or greater.
3. Presentation at the start of treatment for a pulmonary exacerbation of CF.
4. Ability to perform reproducible Pulmonary Function Tests and produce sputum.
5. Willingness to comply with study procedure and willingness to provide written consent.

Exclusion Criteria:

1. Presence of a condition or abnormality that, in the opinion of the Principal Investigator (PI), would compromise the safety of the patient or the quality of the data.
2. Use of systemic steroids

Adult CF patients > 18 years of age undergoing treatment for acute pulmonary exacerbation