Clara cell

Clara cell

Clara cells, now more commonly referred to as club cells, are a type of cell found in the lining of the bronchioles of the lungs. These cells play a crucial role in maintaining and protecting the bronchiolar epithelium. Club cells are non-ciliated, dome-shaped cells that are characterized by their secretory function. They are named after their discoverer, Max Clara, a German anatomist who first described them in 1937. However, the terminology was updated to "club cells" to avoid association with Nazi affiliations.

Function

Club cells serve several important functions in the respiratory system. They produce and secrete a variety of substances, including club cell secretory protein (CCSP), also known as CC16, which has anti-inflammatory and immunomodulatory properties. This protein plays a significant role in protecting the respiratory tract from inflammation and infection. Additionally, club cells are involved in the detoxification of harmful substances inhaled into the lungs, thanks to their cytochrome P450 enzymes. They also contribute to the repair and regeneration of the airway epithelium following injury.

Structure

Club cells are found in the small airways of the lungs, particularly in the bronchioles. They are distinguished by their lack of cilia and their dome-shaped apical surface, which protrudes into the airway lumen. The cells contain a large amount of smooth endoplasmic reticulum and mitochondria, reflecting their active role in secretion and metabolism.

Clinical Significance

Alterations in club cell number or function can be indicative of lung disease. For example, a decrease in the number of club cells or in the levels of CCSP can be observed in various lung conditions, such as chronic obstructive pulmonary disease (COPD), asthma, and pulmonary fibrosis. Therefore, CCSP levels in the blood or bronchoalveolar lavage fluid can serve as a biomarker for lung injury or disease.

Research

Research on club cells and their secretory products continues to provide insights into their roles in lung health and disease. Studies have explored the potential therapeutic applications of CCSP in treating respiratory conditions and its utility as a biomarker for diagnosing and monitoring lung diseases.