Pulmonary Surfactant

Pulmonary surfactant, synthesized by type II alveolar cells and nonciliated epithelial cells (Clara cells), is a surface-active material that reduces the surface tension in the lungs. The main components of surfactant are phospholipids, neutral lipids, serum proteins, and surfactant proteins, including SP-A, SP-B, SPC, and SP-D [159]. Surfactant proteins play integral roles in lowering surface tension and maintaining host defense [159]. SP-B and SP-C are hydrophobic proteins involved primarily in the adsorption and spreading of surfactant phospholipids at the air-liquid interface. SP-A (specific for mannose, glucose, galactose, and fucose) and SP-D (specific for maltose, mannose, and glucose) are hydrophilic proteins that act as the first line of host defense to inhaled pathogens. SP-A and SP-D are members of the collectin subgroup of mammalian C-type lectins that function in host immunity by binding carbohydrate ligands on the surface of invading particles, marking the complexes for destruction by alveolar macrophages [8,160,161]. SP-A stimulates the chemotaxis of alveolar macrophages and enhances their binding to viral and bacterial invaders [8,162]. SP-D binds to alveolar macrophages, polymorphonuclear cells, and various viral, fungal, and bacterial components, thereby playing a role in the regulation of inflammation [163]. As a result, surfactant proteins may reduce the efficiency of gene delivery when DNA vectors contain carbohydrate moieties [8]. For more information on the role of surfactants in the lung, see Refs. 159 and 164.

Coping with Asthma

Coping with Asthma

If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.

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