Collectin

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

## Overview

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Collectins (collagen-containing C-type lectins) are a part of the innate immune system. They form a family of collagenous Ca2+-dependent defense lectins, which are found in animals. Collectins are soluble pattern recognition receptors (PRRs). Their function is to bind to oligosaccharide structure or lipids which are on the surface of microorganisms. Like other PRRs they bind pathogen-associated molecular patterns (PAMPs) and also danger-associated molecular patterns (DAMPs) of oligosaccharide origin. Binding of collectins to microorganisms may trigger elimination of microorganisms by aggregation[disambiguation needed], complement activation, opsonization, activation of phagocytosis or inhibition of microbial growth. Other functions of collectins are modulation of inflammatory, allergic responses, adaptive immune system and clearance of apoptotic cells.

## Structure

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Functionally collectins are trimers. Monomeric subunit consists of four parts:

* A cysteine-rich domain at the N-terminus
* A collagen-like domain
* A coiled-coil neck domain
* A C-type lectin domain that is also called a carbohydrate recognition domain (CRD)

Recognition of specific parts of microorganism is mediated by CRD in presence of calcium.[1][2] Affinity of interaction between microbes and collectins depends on the degree of collectin oligomerization and also on the density of ligands on the surface of the microbe.[3]

## Types of Collectins

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9 types of collectins have been defined to date:

* MBL = mannan-binding lectin (mannose-binding lectin)
* SP-A = surfactant protein A
* SP-D = surfactant protein D
* CL-L1 = collectin liver 1
* CL-P1 = collectin placenta 1
* CL-43 = conglutinin collectin of 43 kDa
* CL-46 = collectin of 46 kDa
* CL-K1 = collectin kidney 1
* Conglutinin

CL-43, CL-46 and conglutinin are found in bovine.

## Function

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### Aggregation

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Collectins can bind on the surface of the microorganism and between carbohydrate ligands can be made a bond. Due to those properties the interaction can result into aggregation.[4][5]

### Opsonization and Activation of Phagocytosis

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Collectins can act as opsonins. There is a specific interaction between collectins and receptors on phagocytic cells which can lead to increased clearance of microorganisms.[6][7][8] MBL can bind to microorganisms and this interaction can lead to opsonization through complement activation,[9] or it can opsonize the microorganism directly.[10] SP-A and SP-D can also interact with microorganisms and phagocytic cells to enhance phagocytosis of the microorganism.[11]

### Inhibition of Microbial Growth

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Collectins have effect on microorganism survival. SP-A and SP-D can bind to LPS (lipopolysaccharide) of both Gram-negative and Gram-positive bacteria. SP-A and SP-D can increase permeability of Gram-negative bacterial cell membrane.[12]

### Modulation of Inflammatory Responses

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SP-A and SP-D can damp induction of inflammation by LPS or endotoxin. It can be caused by removing the LPS or by binding the LPS to CD14 receptor on macrophages which can block the inflammatory response.[13][14][15] SP-A can also bind to TLR2 (Toll-like receptor 2). This interaction causes decrease of TNF-α (Tumor necrosis factor-α) production by alveolar macrophages stimulated with peptidoglycan.[16] SP-A and SP-D can modulate cytokine production. They modulate the production of oxygen and nitrogen reactive species which are very important for phagocytic cells.[17][18][19] SP-A and SP-D has s function as chemoattractants for alveolar neutrophils and monocytes.[20] MBL can recognize peptidoglykan via N-acetylglukosamine. This interaction leads to inhibition of ligand-induced inflammatory by macrophage chemokine production.[21]

### Modulation of the Adaptive Immune System

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SP-A and SP-D can suppress activated T-lymphocytes and IL-2 (interleukin-2) production.[22][23] SP-D increases bacterial antigen presentation by dendritic cells [24] whereas SP-A blocs differentation of the immature dendritic cells.[25]

### Modulation of Allergic Response

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Collectins SP-A and SP-D have anti-allergic effect. They inhibit IgE binding to allergen, decrease histamin release from basophils and inhibit T-lymfocyte production in the late phase of the inflammation.[26][27][28]

### Apoptosis

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Collectins SP-A and SP-D enhance clearance of apoptotic cells by macrophages.[29][30]

### Complement Activation

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Collectins are linked with activation of lectin pathway of complement activation. At the beginning, there is a binding of collectin to PAMPs or DAMPs. Collectin MBL is involved in activation of the lectin complement pathway.[31][32] There are three serine proteases, MASP-1, 2 and 3 (MBL-associated serine proteases), which participate in activation of the lectin pathway. MASP-2 has a cleavage activity and it is essential for forming lectin C3 and C5 convertases and for activation of the complement.[33][34][35]

## Reviews

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For more informations and details see reviews.[36][37][38]

## References

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1. ↑ Weis, W I (1991-11-05). "Physical characterization and crystallization of the carbohydrate-recognition domain of a mannose-binding protein from rat". The Journal of Biological Chemistry. 266 (31): 20678–20686. ISSN 0021-9258. Unknown parameter `|coauthors=` ignored (help)
2. ↑ Weis, W I (1992-11-12). "Structure of a C-type mannose-binding protein complexed with an oligosaccharide". Nature. 360 (6400): 127–134. doi:10.1038/360127a0. ISSN 0028-0836. Unknown parameter `|coauthors=` ignored (help)
3. ↑ Lee, R T (1991-03-15). "Ligand-binding characteristics of rat serum-type mannose-binding protein (MBP-A). Homology of binding site architecture with mammalian and chicken hepatic lectins". The Journal of Biological Chemistry. 266 (8): 4810–4815. ISSN 0021-9258. Unknown parameter `|coauthors=` ignored (help)
4. ↑ Ferguson, J S (1999-07-01). "Surfactant protein D binds to Mycobacterium tuberculosis bacilli and lipoarabinomannan via carbohydrate-lectin interactions resulting in reducedphagocytosis of the bacteria by macrophages". Journal of immunology (Baltimore, Md.: 1950). 163 (1): 312–321. ISSN 0022-1767. Unknown parameter `|coauthors=` ignored (help)
5. ↑ Schelenz, S (September 1995). "Binding of host collectins to the pathogenic yeast Cryptococcus neoformans: human surfactant protein D acts as an agglutinin for acapsular yeast cells". Infection and immunity. 63 (9): 3360–3366. ISSN 0019-9567. Unknown parameter `|coauthors=` ignored (help)
6. ↑ McNeely, T B (July 1994). "Aggregation and opsonization of type A but not type B Hemophilus influenzae by surfactant protein A". American journal of respiratory cell and molecular biology. 11 (1): 114–122. ISSN 1044-1549. Unknown parameter `|coauthors=` ignored (help)
7. ↑ O'Riordan, D M (June 1995). "Surfactant protein D interacts with Pneumocystis carinii and mediates organism adherence to alveolar macrophages". The Journal of Clinical Investigation. 95 (6): 2699–2710. doi:10.1172/JCI117972. ISSN 0021-9738. Unknown parameter `|coauthors=` ignored (help)
8. ↑ Ofek, I (January 2001). "Surfactant protein D enhances phagocytosis and killing of unencapsulated phase variants of Klebsiella pneumoniae". Infection and immunity. 69 (1): 24–33. doi:10.1128/IAI.69.1.24-33.2001. ISSN 0019-9567. Unknown parameter `|coauthors=` ignored (help)
9. ↑ Holmskov, Uffe (2003). "Collections and ficolins: humoral lectins of the innate immune defense". Annual review of immunology. 21: 547–578. doi:10.1146/annurev.immunol.21.120601.140954. ISSN 0732-0582. Unknown parameter `|coauthors=` ignored (help)
10. ↑ Kuhlman, M (1989-05-01). "The human mannose-binding protein functions as an opsonin". The Journal of experimental medicine. 169 (5): 1733–1745. ISSN 0022-1007. Unknown parameter `|coauthors=` ignored (help)
11. ↑ Hartshorn, K L (June 1998). "Pulmonary surfactant proteins A and D enhance neutrophil uptake of bacteria". The American journal of physiology. 274 (6 Pt 1): L958–969. ISSN 0002-9513. Unknown parameter `|coauthors=` ignored (help)
12. ↑ Wu, Huixing (2003-05). "Surfactant proteins A and D inhibit the growth of Gram-negative bacteria by increasing membrane permeability". The Journal of Clinical Investigation. 111 (10): 1589–1602. doi:10.1172/JCI16889. ISSN 0021-9738. Unknown parameter `|coauthors=` ignored (help); Check date values in: `|date=` (help)
13. ↑ van Rozendaal, B A (1999-08-30). "Aerosolized endotoxin is immediately bound by pulmonary surfactant protein D in vivo". Biochimica et Biophysica Acta. 1454 (3): 261–269. ISSN 0006-3002. Unknown parameter `|coauthors=` ignored (help)
14. ↑ Borron, P (2000-04). "Surfactant-associated protein A inhibits LPS-induced cytokine and nitric oxide production in vivo". American journal of physiology. Lung cellular and molecular physiology. 278 (4): L840–847. ISSN 1040-0605. Unknown parameter `|coauthors=` ignored (help); Check date values in: `|date=` (help)
15. ↑ Sano, H (2000-07-21). "Surfactant proteins A and D bind CD14 by different mechanisms". The Journal of Biological Chemistry. 275 (29): 22442–22451. doi:10.1074/jbc.M001107200. ISSN 0021-9258. Unknown parameter `|coauthors=` ignored (help)
16. ↑ Murakami, Seiji (2002-03-01). "Surfactant protein A inhibits peptidoglycan-induced tumor necrosis factor-alpha secretion in U937 cells and alveolar macrophages by direct interaction with toll-like receptor 2". The Journal of Biological Chemistry. 277 (9): 6830–6837. doi:10.1074/jbc.M106671200. ISSN 0021-9258. Unknown parameter `|coauthors=` ignored (help)
17. ↑ Tino, M J (1998-11-19). "Interactions of surfactant protein A with epithelial cells and phagocytes". Biochimica et Biophysica Acta. 1408 (2–3): 241–263. ISSN 0006-3002. Unknown parameter `|coauthors=` ignored (help)
18. ↑ Wright, J R (October 1997). "Immunomodulatory functions of surfactant". Physiological reviews. 77 (4): 931–962. ISSN 0031-9333.
19. ↑ Crouch, E (2001). "Surfactant proteins a and d and pulmonary host defense". Annual review of physiology. 63: 521–554. doi:10.1146/annurev.physiol.63.1.521. ISSN 0066-4278. Unknown parameter `|coauthors=` ignored (help)
20. ↑ Tino, M J (January 1999). "Surfactant proteins A and D specifically stimulate directed actin-based responses in alveolar macrophages". The American journal of physiology. 276 (1 Pt 1): L164–174. ISSN 0002-9513. Unknown parameter `|coauthors=` ignored (help)
21. ↑ Nadesalingam, Jeya (2005-08-01). "Mannose-binding lectin recognizes peptidoglycan via the N-acetyl glucosamine moiety, and inhibits ligand-induced proinflammatory effect and promotes chemokine production by macrophages". Journal of immunology (Baltimore, Md.: 1950). 175 (3): 1785–1794. ISSN 0022-1767. Unknown parameter `|coauthors=` ignored (help)
22. ↑ Borron, P (October 1998). "Surfactant protein A inhibits T cell proliferation via its collagen-like tail and a 210-kDa receptor". The American journal of physiology. 275 (4 Pt 1): L679–686. ISSN 0002-9513. Unknown parameter `|coauthors=` ignored (help)
23. ↑ Borron, P J (1998-11-01). "Recombinant rat surfactant-associated protein D inhibits human T lymphocyte proliferation and IL-2 production". Journal of immunology (Baltimore, Md.: 1950). 161 (9): 4599–4603. ISSN 0022-1767. Unknown parameter `|coauthors=` ignored (help)
24. ↑ Brinker, K G (2001-12). "Surfactant protein D enhances bacterial antigen presentation by bone marrow-derived dendritic cells". American journal of physiology. Lung cellular and molecular physiology. 281 (6): L1453–1463. ISSN 1040-0605. Unknown parameter `|coauthors=` ignored (help); Check date values in: `|date=` (help)
25. ↑ Brinker, Karen G (January 2003). "Surfactant protein A modulates the differentiation of murine bone marrow-derived dendritic cells". American journal of physiology. Lung cellular and molecular physiology. 284 (1): L232–241. doi:10.1152/ajplung.00187.2002. ISSN 1040-0605. Unknown parameter `|coauthors=` ignored (help)
26. ↑ Strong, P (2002-10). "Intranasal delivery of a truncated recombinant human SP-D is effective at down-regulating allergic hypersensitivity in mice sensitized to allergens of Aspergillus fumigatus". Clinical and experimental immunology. 130 (1): 19–24. ISSN 0009-9104. Unknown parameter `|coauthors=` ignored (help); Check date values in: `|date=` (help)
27. ↑ Wang, J Y (November 1996). "Interaction of human lung surfactant proteins A and D with mite (Dermatophagoides pteronyssinus) allergens". Clinical and experimental immunology. 106 (2): 367–373. ISSN 0009-9104. Unknown parameter `|coauthors=` ignored (help)
28. ↑ Wang, J Y (August 1998). "Inhibitory effect of pulmonary surfactant proteins A and D on allergen-induced lymphocyte proliferation and histamine release in children with asthma". American Journal of Respiratory and Critical Care Medicine. 158 (2): 510–518. ISSN 1073-449X. Unknown parameter `|coauthors=` ignored (help)
29. ↑ Vandivier, R William (2002-10-01). "Role of surfactant proteins A, D, and C1q in the clearance of apoptotic cells in vivo and in vitro: calreticulin and CD91 as a common collectin receptor complex". Journal of immunology (Baltimore, Md.: 1950). 169 (7): 3978–3986. ISSN 0022-1767. Unknown parameter `|coauthors=` ignored (help)
30. ↑ Schagat, T L (2001-02-15). "Surfactant protein A enhances alveolar macrophage phagocytosis of apoptotic neutrophils". Journal of immunology (Baltimore, Md.: 1950). 166 (4): 2727–2733. ISSN 0022-1767. Unknown parameter `|coauthors=` ignored (help)
31. ↑ Schwaeble, Wilhelm (2002-09). "The mannan-binding lectin-associated serine proteases (MASPs) and MAp19: four components of the lectin pathway activation complex encoded by two genes". Immunobiology. 205 (4–5): 455–466. doi:10.1078/0171-2985-00146. ISSN 0171-2985. Unknown parameter `|coauthors=` ignored (help); Check date values in: `|date=` (help)
32. ↑ Fujita, Teizo (2002-05). "Evolution of the lectin-complement pathway and its role in innate immunity". Nature reviews. Immunology. 2 (5): 346–353. doi:10.1038/nri800. ISSN 1474-1733. Check date values in: `|date=` (help)
33. ↑ Schwaeble, Wilhelm (2002-09). "The mannan-binding lectin-associated serine proteases (MASPs) and MAp19: four components of the lectin pathway activation complex encoded by two genes". Immunobiology. 205 (4–5): 455–466. doi:10.1078/0171-2985-00146. ISSN 0171-2985. Unknown parameter `|coauthors=` ignored (help); Check date values in: `|date=` (help)
34. ↑ Thiel, S (1997-04-03). "A second serine protease associated with mannan-binding lectin that activates complement". Nature. 386 (6624): 506–510. doi:10.1038/386506a0. ISSN 0028-0836. PMID 9087411. Unknown parameter `|coauthors=` ignored (help)
35. ↑ Schwaeble, Wilhelm J (2011-05-03). "Targeting of mannan-binding lectin-associated serine protease-2 confers protection from myocardial and gastrointestinal ischemia/reperfusion injury". Proceedings of the National Academy of Sciences of the United States of America. 108 (18): 7523–7528. doi:10.1073/pnas.1101748108. ISSN 1091-6490. Unknown parameter `|coauthors=` ignored (help)
36. ↑ van de Wetering, J Koenraad (April 2004). "Collectins: players of the innate immune system". European journal of biochemistry / FEBS. 271 (7): 1229–1249. doi:10.1111/j.1432-1033.2004.04040.x. ISSN 0014-2956. Unknown parameter `|coauthors=` ignored (help)
37. ↑ Gupta, Garima (May 2007). "Collectins: sentinels of innate immunity". BioEssays: news and reviews in molecular, cellular and developmental biology. 29 (5): 452–464. doi:10.1002/bies.20573. ISSN 0265-9247. Unknown parameter `|coauthors=` ignored (help)
38. ↑ Nayak, Annapurna (2012). "An Insight into the Diverse Roles of Surfactant Proteins, SP-A and SP-D in Innate and Adaptive Immunity". Frontiers in immunology. 3: 131. doi:10.3389/fimmu.2012.00131. ISSN 1664-3224. Unknown parameter `|coauthors=` ignored (help)

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Protein: lectins

Animal|

| C-type lectins|

* Asialoglycoprotein receptor
* KLRD1
* Collectin
* Mannan-binding lectin
* Mannose receptor
* proteochondroitin sulfate
* Aggrecan
* Versican
* Brevican
* Neurocan

|

SIGLEC|

* Sialoadhesin
* CD22
* CD33
* Myelin-associated glycoprotein
* SIGLEC5
* SIGLEC7
* SIGLEC8
* SIGLEC9
* SIGLEC10
* SIGLEC12

Other|

* Calnexin
* Calreticulin
* Galectin
* N-Acetylglucosamine receptor
* Selectin

Plant|

* Toxalbumins
* Abrin
* Ricin
* Mitogens
* Concanavalin A
* Phytohaemagglutinin
* Pokeweed mitogen
* Legume lectin
* BanLec

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