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make (cells) more susceptible to the action of phagocytes
process whereby opsonins make an invading microorganism more susceptible to phagocytosis (同)opsonisation

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Action of opsonins: a phagocytic cell recognises the opsonin on the surface of an antigen

An opsonin (from the Greek opsōneîn, to prepare for eating) is any molecule that enhances phagocytosis by marking an antigen for an immune response (i.e., causes the phagocyte to "relish" the marked cell).^[1] However, the term is usually used in reference to molecules that act as binding enhancers for the process of phagocytosis, especially antibodies, which coat the negatively charged molecules on the membrane. Molecules that activate the complement system are also considered opsonins. Phagocytic cells do not have an Fc receptor for immunoglobulin M (IgM),^[2] making IgM ineffective in assisting phagocytosis. However, IgM is extremely efficient at activating complement^[3] and is, therefore, considered an opsonin.^[4] Opsonins can also refer to molecules that target a cell for destruction through the action of natural killer (NK) cells.

Opson in ancient Greece referred to the delicious side-dish of any meal, versus the sitos, or the staple of the meal. Opsonisation is thus the molecular mechanism whereby microbes are chemically modified to be made more "Delicious" for inflammatory phagocytosis.

Mechanism

Both the membrane of a phagocytosing cell and its target have a negative charge (Zeta potential), making it difficult for the two cells to come close together. Once the opsonins attach to the target, however, the negative charge is masked. However, the negative charge of the target does not disappear. The opsonin simply overrides the charge, making it easier for white blood cells (phagocytic cells) to carry out phagocytosis. During the process of opsonization from the Greek word for "to make tasty" (also, opsonisation), antigens are bound by antibody or complement molecules. Phagocytic cells express receptors, CR1 and Fc receptors, that bind opsonin molecules, C3b and antibody, respectively. With the antigen coated in these molecules, binding of the antigen to the phagocyte is greatly enhanced. In fact, most phagocytic binding cannot occur without opsonization of the antigen. Furthermore, opsonization of the antigen and subsequent binding to an activated phagocyte will cause increased expression of complement receptors on neighboring phagocytes.

Mannose-binding lectins contribute in two ways. First, they coat the microbes as opsonins and enhance neutrophil reactivity against them. Second, they activate the lectin pathway of the complement pathway as part of innate immunity and lead to formation of C3b.

Examples

Examples of opsonin molecules include:

Antibodies: IgG and IgM (IgM does not opsonize directly, but does assist in complement fixation and subsequent opsonization by C3b)
Complement proteins: C3b, C4b, and iC3b
Circulating proteins: Mannose-binding lectin and C-reactive protein

The most important are IgG and C3b.^[5]^{[broken citation]}

References

^ Barret, James (1980). Basic Immunology and its Medical Application (2 ed.). St.Louis: The C.V. Mosby Company. ISBN 0-8016-0495-8.
^ Shima, Hideaki; Hiroyuki, Takatsu (2009). "Identification of TOSO/FAIM3 as an Fc receptor for IgM". International Immunology (Oxford Journals) 22 (3): 149–56. doi:10.1093/intimm/dxp121. Retrieved 30 November 2014.
^ Shulman, MJ; Pennel, N (1986). "Activation of complement by immunoglobulin M is impaired by the substitution serine-406----asparagine in the immunoglobulin mu heavy chain" (PDF). Proceedings of the National Academy of Sciences of the United States of America 83 (20): 7678–82. doi:10.1073/pnas.83.20.7678. PMID 3094013. Retrieved 30 November 2014.
^ Williams, MR; Hill, AW (1982). "A role for IgM in the in vitro opsonisation of Staphylococcus aureus and Escherichia coli by bovine polymorphonuclear leucocytes". Research in Veterinary Science (Elsevier) 33 (1): 47–53. PMID 6753075. Retrieved 30 November 2014.
^ Immunology at MCG 1/phagocyt

External links

Opsonins at the US National Library of Medicine Medical Subject Headings (MeSH)

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UpToDate Contents

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1. IgGサブクラス：物理学的性質、遺伝的特徴、および生物学的機能 igg subclasses physical properties genetics and biologic functions
2. 補体経路 complement pathways
3. マンノース結合レクチン欠損症 mannose binding lectin deficiency
4. 新生児の免疫 immunity of the newborn
5. 成人外傷患者における脾損傷のマネージメント management of splenic injury in the adult trauma patient

English Journal

Antibodies to the Plasmodium falciparum Proteins MSPDBL1 and MSPDBL2 Opsonize Merozoites, Inhibit Parasite Growth, and Predict Protection From Clinical Malaria.

Chiu CY1, Hodder AN1, Lin CS1, Hill DL1, Li Wai Suen CS2, Schofield L3, Siba PM4, Mueller I5, Cowman AF1, Hansen DS1.
The Journal of infectious diseases.J Infect Dis.2015 Aug 1;212(3):406-15. doi: 10.1093/infdis/jiv057. Epub 2015 Feb 2.
Increasing evidence suggests that antibodies against merozoite surface proteins (MSPs) play an important role in clinical immunity to malaria. Two unusual members of the MSP-3 family, merozoite surface protein duffy binding-like (MSPDBL)1 and MSPDBL2, have been shown to be extrinsically associated t
PMID 25646353

Protection of mice against Staphylococcus aureus infection by a recombinant protein ClfA-IsdB-Hlg as a vaccine candidate.

Delfani S1, Mohabati Mobarez A, Imani Fooladi AA, Amani J, Emaneini M.
Medical microbiology and immunology.Med Microbiol Immunol.2015 Jul 9. [Epub ahead of print]
Staphylococcus aureus is one of the most important causes of nosocomial infections. An effective vaccine to prevent S. aureus infections is urgently required due to the dramatic increase in the number of antibiotic-resistant strains. In this report, we evaluated a newly recombinant protein composed
PMID 26155981

Characterization of a Human Platelet Antigen-1a-Specific Monoclonal Antibody Derived from a B Cell from a Woman Alloimmunized in Pregnancy.

Eksteen M1, Tiller H2, Averina M3, Heide G1, Kjaer M4, Ghevaert C5, Michaelsen TE6, Ihle Ø7, Husebekk A8, Skogen B4, Stuge TB9.
Journal of immunology (Baltimore, Md. : 1950).J Immunol.2015 Jun 15;194(12):5751-60. doi: 10.4049/jimmunol.1401599. Epub 2015 May 13.
Human platelet Ag (HPA)-1a, located on integrin β3, is the main target for alloantibodies responsible for fetal and neonatal alloimmune thrombocytopenia (FNAIT) in the white population. There are ongoing efforts to develop an Ab prophylaxis and therapy to prevent or treat FNAIT. In this study, an m
PMID 25972474

Japanese Journal

Opsonic Activity of Sera and Blister Fluid from Severely Burned Patients Evaluated by a Chemiluminescence Method

Ono Yasuo,Kunii Otohiko,Suzuki Hiromasa,Ikeda Hirohito,Kobayashi Kunio,Kanegasaki Shiro
MICROBIOLOGY and IMMUNOLOGY 38(5), 373-377, 1994
… These results indicate that blister fluid is also not effective to opsonize bacteria because of the marked depression of the levels of immunoglobulins and complement components. …
NAID 130003484098

ニジマス貪食細胞の貪食活性及び生物化学発光に及ぼす特異免疫血清によるオプソニン化の影響〔英文〕

吉田照豊,北尾忠利
魚病研究 26(1), 29-33, 1991
… When heat-inactivated rainbow trout anti-SRBC serum was used to opsonize SRBC, rates of phagocytic ingestion of SRBC by phagocytes increased with lower dilutions of the antiserum, and CL activities also rose with lower dilutions of the antiserum. …
NAID 130000857722