WordNet

an antibody in blood serum that attaches to invading microorganisms and other antigens to make them more susceptible to the action of phagocytes

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/03/03 03:04:10」(JST)

wiki en

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

An opsonin (from the Latin opsonium, to relish), is any molecule that enhances phagocytosis by marking an antigen for an immune response (i.e., causes the phagocyte to "relish" the marked cell). However, the term is usually used in reference to molecules that act as a binding enhancer 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 IgM, making IgM ineffective in assisting phagocytosis. However, IgM is extremely efficient at activating complement and is, therefore, considered an opsonin. Opsonins can also refer to molecules that target a cell for destruction through the action of natural killer (NK) cells.

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, the negative charged is masked. Take note that the negative charge of the target doesn't 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 (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.

Examples

Examples of opsonin molecules include:

Antibodies: IgG and IgM
Components of the complement system: C3b, C4b, and iC3b
Mannose-binding lectin (initiates the formation of C3b)

The most important are IgG and C3b.^[1]^{[broken citation]}

References

^ Immunology at MCG 1/phagocyt

External links

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

This immunology article is a stub. You can help Wikipedia by expanding it.

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 免疫グロブリンの機能および臨床応用 function and clinical applications of immunoglobulins
2. 新生児の免疫 immunity of the newborn
3. インフルエンザ菌の微生物学、疫学および治療 microbiology epidemiology and treatment of haemophilus influenzae
4. A群レンサ球菌：病原性因子および発症機序 group a streptococcus virulence factors and pathogenic mechanisms
5. HIV非感染の免疫不全患者における発熱および発疹 fever and rash in immunocompromised patients without hiv infection

English Journal

Hemocytes and hemocytic responses in the mole crab Emerita emeritus (Linnaeus 1767).

Thayappan K1, Denis M2, Mullaivanam Ramasamy S2, Munusamy A2.
Journal of invertebrate pathology.J Invertebr Pathol.2017 Sep;148:129-137. doi: 10.1016/j.jip.2017.06.011. Epub 2017 Jun 28.
PMID 28668255

Francisella novicida inhibits spontaneous apoptosis and extends human neutrophil lifespan.

Kinkead LC1,2,3, Fayram DC1,2, Allen LH4,2,3,5.
Journal of leukocyte biology.J Leukoc Biol.2017 Sep;102(3):815-828. doi: 10.1189/jlb.4MA0117-014R. Epub 2017 May 26.
PMID 28550119