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Medawar's theory was critiqued and later further developed by George C. Williams in 1957. Williams noted that senescence may be causing many deaths even if animals are not 'dying of old age.' [1] He began his hypothesis with the idea that ageing can cause earlier senescence due to the competitive nature of life. Even a small amount of ageing ...
The classical complement pathway leading into a complement cascade that is shared with the alternative pathway. The classical pathway is distinct from the other complement pathways in its unique activation triggers and cascade sequence. Activation of the complement pathway through the classical, lectin or alternative complement pathway is ...
The classical and alternative complement pathways. Alternative pathway. (Some labels are in Polish.) 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 ...
The classical and alternative complement pathways. The classical pathway is triggered by activation of the C1-complex. The C1-complex is composed of 1 molecule of C1q, 2 molecules of C1r and 2 molecules of C1s, or C1qr 2 s 2. This occurs when C1q binds to IgM or IgG complexed with antigens. A single pentameric IgM can initiate the pathway ...
Complement-pathways Complement system. C5 convertase is an enzyme belonging to a family of serine proteases that play key role in the innate immunity. It participates in the complement system ending with cell death. There are four different C5 convertases able to specifically convert the protein C5 to C5a and C5b fragments.
In the alternative complement pathway, C3 is cleaved by C3bBb, another form of C3-convertase composed of activated forms of C3 (C3b) and factor B (Bb). Once C3 is activated to C3b, it exposes a reactive thioester that allows the peptide to covalently attach to any surface that can provide a nucleophile such as a primary amine or a hydroxyl ...
Aging theories based on group selection; Antagonistic pleiotropy hypothesis; C. Cross-linking theory of aging; D. Disposable Soma Theory; DNA damage theory of aging; E.
Activation of the C1 complex initiates the classical complement pathway. This occurs when C1q binds to antigen-antibody complexes. The antibodies IgM or certain subclasses of IgG complexed with antigens are able to initiate the complement system: a single pentameric IgM can initiate the pathway, while several monomeric IgG molecules are needed. [3]