Clara cell
Summary
Clara cells (now called club cells) are non-ciliated, dome-shaped epithelial cells found in terminal and respiratory bronchioles. They secrete surfactant protein and Clara cell secretory protein (CCSP), serving as progenitor cells for bronchiolar epithelium repair.
Detail
Club cells (formerly Clara cells, renamed to avoid eponymous terminology) are specialized non-ciliated epithelial cells that comprise 50-60% of the epithelial lining in terminal bronchioles. These dome-shaped cells contain characteristic dense secretory granules and extensive smooth endoplasmic reticulum. They secrete Clara cell secretory protein (CCSP/CC10), which has anti-inflammatory properties and serves as a biomarker for lung injury. Club cells also produce surfactant proteins A and B, and contain cytochrome P450 enzymes that can both detoxify and bioactivate inhaled toxins. Functionally, they serve as facultative progenitor cells, capable of differentiating into ciliated cells during epithelial repair following injury. They play crucial roles in maintaining bronchiolar homeostasis, innate immunity, and xenobiotic metabolism. Loss or dysfunction of club cells is associated with various lung diseases including bronchiolitis obliterans and certain pneumoconioses.
Sources
- Robbins and Cotran Pathologic Basis of Disease
- West's Respiratory Physiology
- Murray and Nadel's Textbook of Respiratory Medicine
- Histology: A Text and Atlas by Ross & Pawlina
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