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(from the article `immune system`) ...antibodies must be bound to antigens (the antigen-antibody complex mentioned above). Free antibodies do not activate complement. To initiate the ...
First component of complement; actually three subcomponents, C1q, C1r and C1s, that form a complex in the presence of calcium ions. C1q, the recognition subunit, has an unusual structure of collagen-like triple helices forming a stalk for its Ig-binding globular heads. Upon binding to immune complexes the C1 complex becomes an active protease that cleaves and activates C4 and C2.
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The C1 was a Canadian blowback operated, selective fire sub-machine-gun produced from 1958 as a modification of the British L2A1 sub-machine-gun. The C1 was chambered for the 9 mm Parabellum cartridge which it took from a 30-round box magazine. It had a cyclic rate of 550 rounds per minute and a muzzle velocity of 366 meters per second. The C1 had ...
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Atlas - first cervical vertebra of the spine