The alternative pathway is a type of cascade reaction of the complement system and is a component of the innate immune system, a natural defense against infections. The alternative pathway is one of three complement pathways that opsonize and kill pathogens.

2022年8月17日 · The alternative pathway of the complement system is a cascade of enzymatic reactions which requires spontaneous hydrolysis of the internal C3 thioester bond. The hydrolyzed protein then binds to serum factor B.

2022年3月20日 · It is activated by certain isotypes of antibodies bound to antigens; the alternative pathway, which is activated on microbial cell surfaces in the absence of antibody; and the lectin pathway, which is activated by a plasma lectin that binds to mannose residues on microbes.

The alternative pathway of complement activation. The AP is activated continuously in plasma by low-grade hydrolysis of C3. The latter binds factor B to form a C3(H 2 O)B complex. CFD cleaves factor B to form the AP initiation C3 convertase that cleaves C3 to C3b.

2023年8月31日 · The alternative complement pathway is activated by C3b binding to microbial surfaces and to antibody molecules. The end results and defense benefits of each pathway, however, are the same. All complement pathways carry out 6 beneficial innate defense functions.

2012年2月2日 · There are three known pathways for complement activation: Classical, Alternative and Lectin pathway. Classical pathway The classical pathway is initiated by IgM or IgG antigen/antibody complexes binding to C1q (first protein of the cascade) leading to activation of C1r, which in turn cleaves C1s.

2024年7月15日 · The alternative complement pathway is a crucial component of the innate immune system, playing an essential role in identifying and clearing pathogens. Unlike other pathways, it can be spontaneously activated, providing a rapid response to potential infections.

The alternative complement pathway is the most ancient complement pathway, identifying, recognizing, attacking, and eliminating microorganisms and modified tissue cells. From: Molecular Immunology, 2009

2024年4月9日 · The alternative pathway (AP) serves as a dominant component of the complement system, surpassing the classical and lectin pathways under normal physiological conditions. Unlike the other pathways, the AP is consistently active at a low level, wherein the hydrolysis of C3 to C3b occurs.

Activation of the alternative complement pathway begins when C3b or C3i binds to the cell wall and other surface components of microbes. C3i can be formed by hydrolysis of C3. The alternative pathway protein factor B then combines with the cell-bound C3b to form C3bB in a magnesium-dependent manner.