Opsonin-independent and -dependent Phagocytosis in the Ascidian Halocynthia roretzi: Galactose-specific Lectin and Complement C3 Function as Target-dependent Opsonins

Azumi, Kaoru; Ishimoto, Rika; Fujita, Takaaki; Nonaka, Masaru; Yokosawa, Hideyoshi

doi:10.2108/zsj.17.625

Cited by 9 publications

(6 citation statements)

References 15 publications

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“…Some of them have a clear role in the recognition of foreign molecules or in the modulation of immune responses (36, 65, 85–88). In most cases, they enhance the phagocytosis of microorganisms acting as opsonins (86, 87, 89, 90). Lectins can also trigger the respiratory burst and act as molecules able to influence the behavior of other immunocytes, as in the case of the Botryllus rhamnose-binding lectin (BsRBL) (37), or to activate the complement system (46).…”

Section: Humoral Defensive Repertoirementioning

confidence: 99%

“…C3-a can recruit hemocytes to the inflammation site (102) via its binding to a G protein-coupled receptor, constitutively expressed in PO-containing hemocytes (103). C3b, the main C3 fragment, can adhere to the microbial surfaces and exert an opsonic role enhancing the recognition and ingestion of bacteria by phagocytes (89, 97, 98, 100, 104). …”

Section: Humoral Defensive Repertoirementioning

confidence: 99%

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Immunity in Protochordates: The Tunicate Perspective

Franchi

Ballarin

2017

Front. Immunol.

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Tunicates are the closest relatives of vertebrates, and their peculiar phylogenetic position explains the increasing interest toward tunicate immunobiology. They are filter-feeding organisms, and this greatly influences their defense strategies. The majority of the studies on tunicate immunity were carried out in ascidians. The tunic acts as a first barrier against pathogens and parasites. In addition, the oral siphon and the pharynx represent two major, highly vascularized, immune organs, where circulating hemocytes can sense non-self material and trigger immune responses that, usually, lead to inflammation and phagocytosis. Inflammation involves the recruitment of circulating cytotoxic, phenoloxidase (PO)-containing cells in the infected area, where they degranulate as a consequence of non-self recognition and release cytokines, complement factors, and the enzyme PO. The latter, acting on polyphenol substrata, produces cytotoxic quinones, which polymerize to melanin, and reactive oxygen species, which induce oxidative stress. Both the alternative and the lectin pathways of complement activation converge to activate C3: C3a and C3b are involved in the recruitment of hemocytes and in the opsonization of foreign materials, respectively. The interaction of circulating professional phagocytes with potentially pathogenic foreign material can be direct or mediated by opsonins, either complement dependent or complement independent. Together with cytotoxic cells, phagocytes are active in the encapsulation of large materials. Cells involved in immune responses, collectively called immunocytes, represent a large fraction of hemocytes, and the presence of a cross talk between cytotoxic cells and phagocytes, mediated by secreted humoral factors, was reported. Lectins play a pivotal role as pattern-recognition receptors and opsonizing agents. In addition, variable region-containing chitin-binding proteins, identified in the solitary ascidian Ciona intestinalis, control the settlement and colonization of bacteria in the gut.

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Section: Humoral Defensive Repertoirementioning

confidence: 99%

Section: Humoral Defensive Repertoirementioning

confidence: 99%

Immunity in Protochordates: The Tunicate Perspective

Franchi

Ballarin

2017

Front. Immunol.

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“…Purified galactose-specific lectin, which is present in large amounts in H. roretzi hemolymph plasma, strongly enhances the phagocytosis of sheep erythrocytes by H. roretzi hemocytes, which suggests that it is a candidate opsonin. Moreover, it is interesting that galactose-specific lectin induces active oxygen (O 2 − ) production by mammalian leucocytes (Azumi et al, 2000). H. roretzi hemocytes produce O 2 − in response to treatment with zymosan, thus, indicating that galactose-specific lectin regulates several cellular reactions in the host defense system (Vasta et al, 1999).…”

Section: The Solitary Ascidian (Halocynthia (H) Roretzi)mentioning

confidence: 99%

Recent Advances in the Innate Immunity of Invertebrate Animals

Iwanaga¹,

Lee²

2005

BMB Reports

514

380

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Invertebrate animals, which lack adaptive immune systems, have developed other systems of biological host defense, so called innate immunity, that respond to common antigens on the cell surfaces of potential pathogens. During the past two decades, the molecular structures and functions of various defense components that participated in innate immune systems have been established in Arthropoda, such as, insects, the horseshoe crab, freshwater crayfish, and the protochordata ascidian. These defense molecules include phenoloxidases, clotting factors, complement factors, lectins, protease inhibitors, antimicrobial peptides, Toll receptors, and other humoral factors found mainly in hemolymph plasma and hemocytes. These components, which together compose the innate immune system, defend invertebrate from invading bacterial, fungal, and viral pathogens. This review describes the present status of our knowledge concerning such defensive molecules in invertebrates.

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“…Hemocytes that ingested at least one yeast were considered positive. The degree of phagocytosis was expressed as the ratio of the number of positive hemocytes to the number of total hemocytes (21).…”

Section: Phagocytosis Assaymentioning

confidence: 99%

“…The entire amino acid sequences of the ascidian p36 and human (Hu), rat (Ra), and mouse (Mo) MBLs were aligned using ClustalW software with reference to the invariant residues of C-type lectins (21). The signal peptide cleavage site is indicated by an arrowhead.…”

Section: Figurementioning

confidence: 99%

An Ancient Lectin-Dependent Complement System in an Ascidian: Novel Lectin Isolated from the Plasma of the Solitary Ascidian, Halocynthia roretzi

Sekine

Kenjo²,

Azumi

et al. 2001

The Journal of Immunology

Self Cite

123

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Mannose-binding lectin (MBL) is a C-type lectin involved in the first line of host defense against pathogens and it requires MBL-associated serine protease (MASP) for activation of the complement lectin pathway. To elucidate the origin and evolution of MBL, MBL-like lectin was isolated from the plasma of a urochordate, the solitary ascidian Halocynthia roretzi, using affinity chromatography on a yeast mannan-Sepharose. SDS-PAGE of the eluted proteins revealed a major band of ∼36 kDa (p36). p36 cDNA was cloned from an ascidian hepatopancreas cDNA library. Sequence analysis revealed that the carboxy-terminal half of the ascidian lectin contains a carbohydrate recognition domain (CRD) that is homologous to C-type lectin, but it lacks a collagen-like domain that is present in mammalian MBLs. Purified p36 binds specifically to glucose but not to mannose or N-acetylglucosamine, and it was designated glucose-binding lectin (GBL). The two ascidian MASPs associated with GBL activate ascidian C3, which had been reported to act as an opsonin. The removal of GBL-MASPs complex from ascidian plasma using Ab against GBL inhibits C3-dependent phagocytosis. These observations strongly suggest that GBL acts as a recognition molecule and that the primitive complement system, consisting of the lectin-proteases complex and C3, played a major role in innate immunity before the evolution of an adaptive immune system in vertebrates.

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Opsonin-independent and -dependent Phagocytosis in the Ascidian Halocynthia roretzi: Galactose-specific Lectin and Complement C3 Function as Target-dependent Opsonins

Cited by 9 publications

References 15 publications

Immunity in Protochordates: The Tunicate Perspective

Immunity in Protochordates: The Tunicate Perspective

Recent Advances in the Innate Immunity of Invertebrate Animals

An Ancient Lectin-Dependent Complement System in an Ascidian: Novel Lectin Isolated from the Plasma of the Solitary Ascidian, Halocynthia roretzi

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