IC3b

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iC3b is a protein molecule that is used in medical research because of its ability to bind to specific target cells. This is useful for basic research, and in some cases it is possible to get the immune system to attack those cells, thus opening the possibility of new cancer treatments.

Protein biological molecule consisting of chains of amino acid residues

Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific three-dimensional structure that determines its activity.

Medical research research

Biomedical research encompasses a wide array of research, extending from "basic research", – involving fundamental scientific principles that may apply to a preclinical understanding – to clinical research, which involves studies of people who may be subjects in clinical trials. Within this spectrum is applied research, or translational research, conducted to expand knowledge in the field of medicine.

Agonist chemical substance which, upon binding to a receptor, leads to its activation

An agonist is a chemical that binds to a receptor and activates the receptor to produce a biological response. Whereas an agonist causes an action, an antagonist blocks the action of the agonist, and an inverse agonist causes an action opposite to that of the agonist.

iC3b is a proteolytically inactive product of the complement cleavage fragment C3b [1] that still opsonizes microbes, but cannot associate with factor B, thus preventing amplification of the complement cascade or activation through the alternative pathway.

C3b

C3b is the larger of two elements formed by the cleavage of complement component 3, and is considered an important part of the innate immune system. C3b is potent in opsonization: tagging pathogens, immune complexes (antigen-antibody), and apoptotic cells for phagocytosis. Additionally, C3b plays a role in forming a C3 convertase when bound to Factor B, or a C5 convertase when bound to C4b and C2b or when an additional C3b molecule binds to the C3bBb complex.

Related Research Articles

Hypersensitivity refers to undesirable reactions produced by the normal immune system, including allergies and autoimmunity. They are usually referred to as an over-reaction of the immune system and these reactions may be damaging, uncomfortable, or occasionally fatal. Hypersensitivity reactions require a pre-sensitized (immune) state of the host. They are classified in four groups after the proposal of P. G. H. Gell and Robin Coombs in 1963.

Complement system part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promotes inflammation, and attacks the pathogens cell membrane

The complement system is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promotes inflammation, and attacks the pathogen's cell membrane. It is part of the innate immune system, which is not adaptable and does not change over the course of an individual's lifetime. The complement system can, however, be recruited and brought into action by antibodies generated by the adaptive immune system.

Xenotransplantation, or heterologous transplant is the transplantation of living cells, tissues or organs from one species to another. Such cells, tissues or organs are called xenografts or xenotransplants. It is contrasted with allotransplantation, syngeneic transplantation or isotransplantation and autotransplantation.

Classical complement pathway Any process involved in the activation of any of the steps of the classical pathway of the complement cascade which allows for the direct killing of microbes, the disposal of immune complexes, and the regulation of other immune processes.

The classical complement pathway is one of three pathways which activate the complement system, which is part of the immune system. The classical complement pathway is initiated by antigen-antibody complexes with the antibody isotypes IgG and IgM.

Alternative complement pathway Any process involved in the activation of any of the steps of the alternative pathway of the complement cascade which allows for the direct killing of microbes and the regulation of other immune processes.

The alternative pathway of the complement system is an innate component of the immune system's natural defense against infections.

C3-convertase

C3 convertase belongs to family of serine proteases and is necessary in innate immunity as a part of the complement system which eventuate in opsonisation of particles, release of inflammatory peptides, C5 convertase formation and cell lysis.

Opsonin

An opsonin is any molecule that enhances phagocytosis by marking an antigen for an immune response or marking dead cells for recycling. Opson in ancient Greece referred to the delicious side-dish of any meal, versus the sitos, or the staple of the meal.

Complement membrane attack complex

The membrane attack complex (MAC) or terminal complement complex (TCC) is a structure typically formed on the surface of pathogen cell membranes as a result of the activation of the host's complement system, and as such is one of the effector proteins of the immune system. The membrane-attack complex (MAC) forms transmembrane channels. These channels disrupt the cell membrane of target cells, leading to cell lysis and death.

An autoantibody is an antibody produced by the immune system that is directed against one or more of the individual's own proteins. Many autoimmune diseases are caused by such autoantibodies.

Complement component 3 protein-coding gene in the species Homo sapiens

Complement component 3, often simply called C3, is a protein of the immune system. It plays a central role in the complement system and contributes to innate immunity. In humans it is encoded on chromosome 19 by a gene called C3.

During the activation of lymphocytes, co-stimulation is often crucial to the development of an effective immune response. Co-stimulation is required in addition to the antigen-specific signal from their antigen receptors.

Integrin alpha M protein-coding gene in the species Homo sapiens

Integrin alpha M (ITGAM) is one protein subunit that forms heterodimeric integrin alpha-M beta-2 (αMβ2) molecule, also known as macrophage-1 antigen (Mac-1) or complement receptor 3 (CR3). ITGAM is also known as CR3A, and cluster of differentiation molecule 11B (CD11B). The second chain of αMβ2 is the common integrin β2 subunit known as CD18, and integrin αMβ2 thus belongs to the β2 subfamily integrins.

C3a receptor protein-coding gene in the species Homo sapiens

The C3a receptor also known as complement component 3a receptor 1 (C3AR1) is a G protein-coupled receptor protein involved in the complement system.

Complement receptor 2 protein-coding gene in the species Homo sapiens

Complement receptor type 2 (CR2), also known as complement C3d receptor, Epstein-Barr virus receptor, and CD21, is a protein that in humans is encoded by the CR2 gene.

C5a receptor protein-coding gene in the species Homo sapiens

The C5a receptor also known as complement component 5a receptor 1 (C5AR1) or CD88 is a G protein-coupled receptor for C5a. It functions as a complement receptor. C5a receptor modulates inflammatory responses, obesity, development and cancers.

Macrophage-1 antigen is a complement receptor ("CR3") consisting of CD11b and CD18.

Type III hypersensitivity An inflammatory response resulting from recognition of immune complexes via complement or Fc receptors on effector cells leading to activation of neutrophils and other leukocytes and damage to bystander tissue.

Type III hypersensitivity occurs when there is accumulation of immune complexes that have not been adequately cleared by innate immune cells, giving rise to an inflammatory response and attraction of leukocytes. Such reactions may progress to immune complex diseases.

C3a (complement)

C3a is one of the proteins formed by the cleavage of complement component 3; the other is C3b. C3a is a 77 residue anaphylatoxin that binds to the C3a receptor (C3aR), a class A G protein-coupled receptor. It plays a large role in the immune response.

Type 4 hypersensitivity is often called delayed type hypersensitivity as the reaction takes several days to develop. Unlike the other types, it is not antibody-mediated but rather is a type of cell-mediated response.

References

  1. ↑ Robbins Basic Pathology 8th ed 2007. R Cotran, S Robbins, V Kumar, J Perkins. W.B. Saunders Company.


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