The Complement Cascade The Alternative Pathway Complement The
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The Complement Cascade The Alternative Pathway
Complement: The Alternative Pathway C 3 a C 3 b C 3 breaks down to C 3 a and C 3 b spontaneously at a slow rate Next
Complement: The Alternative Pathway C 3 b. B FB C 3 b (In the presence of Mg 2+ ions) Factor B binds to C 3 b Forming C 3 b. B Next
Complement: The Alternative Pathway C 3 b. Bb FD C 3 b. B FB C 3 b Factor D cleaves C 3 b. B Forming C 3 b. Bb Next
Complement: The Alternative Pathway FP C 3 b. Bb Microbial surface FD C 3 b. B FB C 3 b. Bb is unstable, with a very short half life It is stabilised by FP which is active of microbial surfaces Next
Complement: The Alternative Pathway • C 3 b. Bb is termed the Alternative C 3 Convertase • C 3 b. Bb cleaves C 3 to produce C 3 b • (C 3 a is released) • C 3 b is the first molecule of the Terminal Pathway Next
Complement: The Alternative Pathway C 3 b. Bb FD C 3 a C 3 b. B FB C 3 b. Bb cleaves C 3 producing C 3 a and C 3 b Next
Complement: The Alternative Pathway C 3 b. Bb • This is a positive feedback mechanism FD C 3 a C 3 b. B FB C 3 b • It enables the amplification of the complement process • Positive feedback mechanisms are relatively rare because they are inherently unstable • Hence, positive feedback mechanisms have controls to regulate them and to maintain homeostasis. • Factor H performs this role in the Alternative Pathway Next
Complement: The Alternative Pathway C 3 b. Bb FD C 3 a C 3 b. B If athe In bacterial absence surface of is infection, FB present, FHbinds. C 3 b in preference to FH FB FB C 3 b. H FH Factor H competes with FB to bind C 3 b forming C 3 b. H Next
Complement: The Alternative Pathway C 3 b. Bb FD C 3 a FI C 3 b. B C 3 b. i. H FB C 3 b. H C 3 b. i FH Factor I binds C 3 b. H – forming C 3 b. i. H FH is then released – recycling FH Next
Complement: The Alternative Pathway C 3 b. Bb FD C 3 a FI C 3 b. B C 3 b. i. H FB C 3 c C 3 b. H C 3 b. i C 3 d FH C 3 b. i. spontaneously breaks down to C 3 c and C 3 d Next
Complement: The Alternative Pathway C 3 b. Bb FD C 3 a C 3 b. B FB C 3 b is the first component of the Terminal Pathway (Click Here)
