classical pathway

(noun)

a group of blood proteins that mediate the specific antibody response

Related Terms

Examples of classical pathway in the following topics:

  • The Complement System

    • Three biochemical pathways activate the complement system: the classical complement pathway, the alternative complement pathway, and the lectin pathway.
    • n the classical pathway, C1 binds with its C1q subunits to Fc fragments (made of CH2 region) of IgG or IgM, which forms a complex with antigens.
    • shows the classical and the alternative pathways with the late steps of complement activation schematically.
    • In the classical pathway, C4 binds to Ig-associated C1q and C1r2s2 enzyme cleaves C4 to C4b and 4a.
    • The classical and the alternative pathways with the late steps of complement activation.

  • The Complement System

    • Activation of the complement leads to robust and efficient proteolytic cascades, which terminate in opsonization and lysis of the pathogen as well as in the generation of the classical inflammatory response through the production of potent proinflammatory molecules.
    • The complement system can be activated through three major pathways: classical, lectin, and alternative.
    • Initiation of the classical pathway occurs when C1q, in complex with C1r and C1s serine proteases (the C1 complex), binds to the Fc region of complement-fixing antibodies (generally IgG1and IgM) attached to pathogenic surfaces.
    • Further study in animals bearing natural complement deficiencies implicated the classical pathway as a crucial mechanism for efficient antigen trapping and retention in lymphoid tissues (e.g., splenic follicles), suggesting that a major function of the complement system was to localize foreign antigens into immune sites important for lymphocytes responses.

  • Type II (Cytotoxic) Reactions

    • IgG and IgM antibodies bind to these antigens to form complexes that activate the classical pathway of complement activation to eliminate cells presenting foreign antigens (which are usually, but not in this case, pathogens).
    • The membrane attack complex (MAC; ) is typically formed on the surface of pathogenic bacterial cells as a result of the activation of the alternative pathway and the classical pathway of the complement system, and it is one of the effector proteins of the immune system.

  • Steroids

    • Steroid biosynthesis is an anabolic metabolic pathway that produces steroids from simple precursors.
    • A unique biosynthetic pathway is followed in animals compared to many other organisms, making the pathway a common target for antibiotics and other anti-infective drugs.
    • The non-mevalonate pathway or 2-C-methyl-D-erythritol 4-phosphate/1-deoxy-D-xylulose 5-phosphate pathway (MEP/DOXP pathway) of isoprenoid biosynthesis is an alternative metabolic pathway leading to the formation of isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP).
    • The classical mevalonate pathway or HMG-CoA reductase pathway is an important cellular metabolic pathway present in all higher eukaryotes and many bacteria.
    • In contrast to the classical mevalonate pathway of isoprenoid biosynthesis, plants and apicomplexan protozoa such as malaria parasites have the ability to produce their isoprenoids (terpenoids) using an alternative pathway, the non-mevalonate pathway, which takes place in their plastids.

  • The Entner–Doudoroff Pathway

    • The Entner–Doudoroff pathway is an alternate series of reactions that catabolize glucose to pyruvate.
    • The Entner–Doudoroff pathway describes an alternate series of reactions that catabolize glucose to pyruvate using a set of enzymes different from those used in either glycolysis or the pentose phosphate pathway .
    • Most bacteria use glycolysis and the pentose phosphate pathway.
    • This pathway was first reported in 1952 by Michael Doudoroff and Nathan Entner.
    • There are a few bacteria that substitute classic glycolysis with the Entner-Doudoroff pathway.

  • Interferons

    • STAT activation initiates the most well-defined cell signaling pathway for all IFNs, the classical Janus kinase-STAT (JAK-STAT) signaling pathway.
    • In this pathway, JAKs associate with IFN receptors and, following receptor engagement with IFN, phosphorylate both STAT1 and STAT2.
    • In addition to the JAK-STAT pathway, IFNs can activate several other signaling cascades.
    • Both type I and type II IFNs activate a member of the CRK family of adaptor proteins called CRKL, a nuclear adaptor for STAT5 that also regulates signaling through the C3G/Rap1 pathway.
    • The phosphatidylinositol 3-kinase (PI3K) signaling pathway is also regulated by both type I and type II IFNs.

  • Substrates for Biosynthesis

    • These pathways are necessary for survival and cellular function.
    • These processes require pathways that are often multi-step.
    • An additional central metabolic pathway includes glycolysis.
    • Additional pathways that require substrates or metabolites produced by the glycolytic pathway include: gluconeogenesis, lipid metabolism, the pentose phosphate pathway, and the TCA.
    • An overview of the glycolytic pathway.

  • Complement Fixation

    • Complement fixation is a classic method for demonstrating the presence of antibody in patient serum.

  • The Acetyl-CoA Pathway

    • The acetyl coenzyme A (CoA) pathway, commonly referred to as the Wood-Ljungdahl pathway or the reductive acetyl-CoA pathway, is one of the major metabolic pathways utilized by bacteria.
    • The following is a brief overview of the acetyl-CoA pathway. .
    • The acetyl-CoA pathway begins with the reduction of a carbon dioxide to carbon monoxide.
    • Acetyl-CoA synthetase is a class of enzymes that is key to the acetyl-CoA pathway.
    • Methanogens are able to utilize the acetyl-CoA pathway to fix carbon dioxide.

  • The 3-Hydroxypropionate Cycle

    • The 3-hydroxypropionate cycle is a carbon fixation pathway that results in the production of acetyl-CoA and glyoxylate.
    • Carbon fixation is a key pathway in numerous microorganisms, resulting in the formation of organic compounds deemed necessary for cellular processes.
    • One of the pathways that is utilized for carbon fixation is the 3-hydroxypropionate cycle.
    • The ability of Chloroflexus aurantiacus to utilize this pathway is unique.
    • An image of Chloroflexus aurantiacus, a green nonsulfur bacteria that utilizes the 3-hydroxypropionate pathway.