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Typus
BauernOpfer
Bearbeiter
Hindemith
Gesichtet
Yes.png
Untersuchte Arbeit:
Seite: 17, Zeilen: 18-34
Quelle: Fehrenbach 2001
Seite(n): 35, Zeilen: r.col: 17ff
The other function of alveolar surfactant relies on the nature of SP-A and SP-D as collectins. Both proteins are able to bind to the surface of various pathogens, thus acting as opsonins to facilitate their elimination by alveolar macrophages. Therefore, alveolar surfactant is also responsible for host defence (Crouch, 2000; Pison et al., 1994; Wright, 1998).

Surfactant is synthesized by alveolar type II epithelial cells and released upon appropriate stimuli by exocytosis from special intracellular storage organelles termed lamellar bodies. Once released into the alveolar space, freshly secreted lamellar body material undergoes several steps of transformation that are necessary to establish the surface-active lining layer. Cyclic compression and expansion during ventilation result in a fraction of spent surfactant that will largely be recycled by AECII. Thus, single constituents of surfactant run through several cycles before being removed by alveolar macrophages and replaced by de novo synthesis (Fehrenbach, 2001).

Although the bronchiolar Clara cells and submucosal cells also synthesize and release the mature proteins SP-A, SP-B and SP-D (Kalina et al., 1992; Voorhout et al., 1992) the alveolar type II epithelial cell is the only type of pulmonary cell that [produces all surfactant components including phospholipids as well as all four surfactant proteins. The mature 3.5 -3.7kDa small SP-C is thought to be exclusively released by AECII cells (Beers et al., 1994; Phelps and Floros et al., 1991).]


Beers MF, Kim CY, Dodia C, Fisher AB. Localization, synthesis, and processing of surfactant protein SP-C in rat lung analyzed by epitope-specific antipeptide antibodies. J Biol Chem. 1994 Aug 12; 269 (32): 20318-28.

Crouch EC. Surfactant protein-D and pulmonary host defense. Respir Res. 2000; 1 (2): 93-108. Epub 2000 Aug 25. Review.

Fehrenbach H. Alveolar epithelial type II cell: defender of the alveolus revisited. Respir Res. 2001; 2 (1): 33-46. Epub 2001 Jan 15. Review.

Kalina M, Mason RJ, Shannon JM. Surfactant protein C is expressed in alveolar type II cells but not in Clara cells of rat lung. Am J Respir Cell Mol Biol. 1992 Jun; 6 (6): 594-600.

Phelps DS, Floros J. Localization of pulmonary surfactant proteins using immunohistochemistry and tissue in situ hybridization. Exp Lung Res. 1991 Nov-Dec; 17 (6): 985-95.

Pison U, Max M, Neuendank A, Weissbach S, Pietschmann S. Host defence capacities of pulmonary surfactant: evidence for 'non-surfactant' functions of the surfactant system. Eur J Clin Invest. 1994 Sep; 24 (9): 586-99. Review.

Voorhout WF, Veenendaal T, Kuroki Y, Ogasawara Y, van Golde LM, Geuze HJ. Immunocytochemical localization of surfactant protein D (SP-D) in type II cells, Clara cells, and alveolar macrophages of rat lung. J Histochem Cytochem. 1992 Oct; 40 (10): 1589-97.

Wright JR. Host defense functions of surfactant In Lung surfactant:cellular and molecular processing. Edited by Ronney SA. Austin, Texas; R. G. Landes Company, 1998: 191-214.

Another function of alveolar surfactant postulated by Macklin [1], host defence, has attracted major scientific interest in recent years (for reviews, see [32,33]). This function of surfactant relies on the nature of SP-A and SPD as collectins. Both proteins are able to bind to the surface of various pathogens, thus acting as opsonins to facilitate their elimination by alveolar macrophages [32–34]. [...]

[...] It is synthesised by the AE2 cells and released upon appropriate stimuli by exocytosis from special intracellular storage organelles termed lamellar bodies. Once released into the alveolar space, freshly secreted lamellar body material undergoes several steps of transformation that are necessary to establish the surface-active lining layer. Cyclic compression and expansion during ventilation result in a fraction of spent surfactant that will largely be recycled by the AE2 cells. Thus, single constituents of surfactant may run through several cycles before being removed by alveolar macrophages and replaced by de novo synthesis (for comprehensive review, see [11]).

Synthesis

Although the bronchiolar Clara cells synthesise and release the mature proteins SP-A, SP-B, and SP-D (Fig. 2a) [37,38], the AE2 cell is the only type of pulmonary cell that produces all the surfactant components (phospholipids [Fig. 3] as well as all four surfactant proteins). The mature 3.5–3.7 kDa small SP-C (Fig. 2b) is thought to be released by AE2 cells only [39,40].


1. Macklin CC: The pulmonary alveolar mucoid film and the pneumonocytes. Lancet 1954, 29:1099–1104.

11. Rooney SA: Lung surfactant: cellular and molecular processing. Austin, Texas, RG Landes Company, 1998.

32. Pison U, Max M, Neuendank A, Weissbach S, Pietschmann S: Host defence capacities of pulmonary surfactant: evidence for ‘non- surfactant’ functions of the surfactant system. Eur J Clin Invest 1994, 24:586–599.

33. Wright JR: Host defense functions of surfactant. In Lung surfactant: cellular and molecular processing. Edited by Rooney SA. Austin, Texas; R. G. Landes Company, 1998:191–214.

34. Crouch EC: Surfactant protein-D and pulmonary host defense. Respir Res 2000, 1:93–108.

37. Kalina M, Mason RJ, Shannon JM: Surfactant protein C is expressed in alveolar type II cells but not in Clara cells of rat lung. Am J Respir Cell Mol Biol 1992, 6:594–600.

38. Voorhout WF, Veenendaal T, Kuroki Y, Ogasawara Y, van Golde LM, Geuze HJ: Immunocytochemical localization of surfactant protein D (SP-D) in type II cells, Clara cells, and alveolar macrophages of rat lung. J Histochem Cytochem 1992, 40: 1589–1597.

39. Phelps DS, Floros J: Localization of pulmonary surfactant proteins using immunohistochemistry and tissue in situ hybridization. Exp Lung Res 1991, 17:985–995.

40. Beers MF, Kim CY, Dodia C, Fisher AB: Localization, synthesis, and processing of surfactant protein SP-C in rat lung analyzed by epitope-specific antipeptide antibodies. J Biol Chem 1994, 269:20318–20328.

Anmerkungen

The source is mentioned on the last line of the second paragraph. It is not clear to the reader that the preceding two as well as the following two paragraphs are taken from the source almost literally, together with several references to the literature.

To be continued on the next page: Mag/Fragment_018_01

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(Hindemith), WiseWoman

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