A549 cells are a human lung adenocarcinoma cell line commonly used in biomedical research. These cells were originally derived from a lung tumor biopsy taken from a male patient with lung cancer in the 1970s. A549 cells are widely used as an in vitro model for studying lung cancer and other lung diseases.

A549 cells have been characterized as having properties of type II alveolar epithelial cells, which are the cells responsible for producing surfactant in the lungs. They express markers characteristic of alveolar epithelial cells, including surfactant protein A, surfactant protein B, and cytokeratin 18.

A549 cells have been used in a variety of research applications, including studying the molecular mechanisms of lung cancer, screening potential anti-cancer drugs, and investigating the effects of environmental pollutants and toxicants on lung cells. They are also commonly used in virology research, including studies of respiratory viruses such as influenza and coronavirus.