CC16

CC16, also known as Clara cell secretory protein, CC16, uteroglobin, or SCGB1A1, is a small secreted protein produced by Clara cells of the bronchial epithelium in humans. The gene SCGB1A1 encodes the protein, which belongs to the secretoglobin family. CC16 is secreted into the airway lumen and can also be detected in serum, where its level reflects the integrity of the lung epithelium.

In terms of structure and localization, CC16 is a relatively small secreted protein, commonly described as having a molecular weight of about 16 kilodaltons. It is predominantly expressed in the conducting airways, with secretion contributing to the composition of the airway surface liquid and to systemic circulation when the epithelial barrier is permeable or damaged.

Functionally, CC16 is believed to have anti-inflammatory and immunomodulatory properties. It is thought to participate in regulating airway inflammation and protecting the epithelial surface, potentially by modulating leukocyte recruitment and inflammatory signaling. Its presence in airway secretions and serum suggests a role in both local defense and systemic readouts of lung health.

Clinically, CC16 serves as a biomarker of lung epithelial integrity. Serum levels tend to be reduced in conditions associated with epithelial injury or cigarette smoke exposure, such as chronic obstructive pulmonary disease and certain inflammatory lung diseases. Conversely, elevated serum CC16 can indicate increased alveolar-capillary barrier permeability in acute lung injury or other forms of lung damage. CC16 measurements are used in research and, in some contexts, in clinical studies to assess exposure, airway injury, or disease progression.

Research on CC16 continues to explore its precise mechanisms, diagnostic utility, and potential therapeutic implications in pulmonary medicine.