Complement pathway

Question 1

three complement pathways

Answer 1

classical

alternative

lectin

Question 2

the classical pathway is initiated when… are present

Answer 2

• a suitable Ab bound to antigen (Ag)
• complement components 1, 4, 2 and 3
• Ca++ and Mg++ cations

Question 3

classical pathway.. C1 activation

Answer 3

Binding of C1qrs (a calcium-dependent complex), present in normal serum, to Ag-Ab complexes results in autocatalysis of C1r. The altered C1r cleaves C1s and this cleaved C1s becomes an enzyme (C4-C2 convertase) capable of cleaving both C4 and C2.

Question 4

classical pathway…C4 and C2 activation by C1 causes…

Answer 4

C4 –> C4a and C4b

C4b binds C2 which becomes susceptible to C1s and is cleaved into C2a and C2b

C2a becomes complexed with C4b

C4b2a complex, is known as C3 convertase

–> leading to the second part of the complement cascade which starts with C3 (same for all three pathways)

Question 5

mnemonic for CP

Answer 5

Class 142

1= Q1rs

4= C4

2= C2

Question 6

the lectin pathway is initiated when… are present

Answer 6

This pathway is initiated by three proteins: a mannan-binding lectin (MBL), which interacts with two mannan-binding lectin-associated serine proteases (MASP and MADSP2), analogous to C1r and C1s.

Question 7

lectin pathway is…. independent

Answer 7

antibody

Question 8

lectin pathway…C4 and C2 are activated by…

Answer 8

MBL and MASPS

Question 9

MBL/MASPS are analogous with

Answer 9

C1qrs

Question 10

pathway…C4 and C2 activation by MBL causes…

Answer 10

activation of C3 convertase which activates C3 (start of part two of pathway)

Question 11

the alternative pathway is different because it includes

Answer 11

spontaneous activation of C3

Question 12

the alternative pathway is initiated when… are present

Answer 12

begins with the activation of C3 and requires Factors B and D and Mg++ cation, all present in normal serum

Question 13

alternative pathway process

Answer 13

invoices the spontaneous activation of C3, which leads to the involvement of C3b, D, B and p factors which leads to the activation of C3 convertase- activation of part tow of the pathway

Question 14

the lytic pathway- which comes after the first part of the pathway (CP,LP,AP)… involves which C proteins

Answer 14

C5-9
- C5 convertase generated by the classical or alternative pathway cleaves C5 into C5a and C5b. C5b binds C6 and subsequently C7 to yield a hydrophobic C5b67 complex which attaches quickly to the plasma membrane (Figure 7). Subsequently, C8 binds to this complex and causes the insertion of several C9 molecules. bind to this complex and lead to formation of a hole in the membrane resulting in cell lysis

Question 15

what does the lytic pathway produce

Answer 15

the MAC

- membrane attack complex–> causes uncontrolled diffusion of ions–> lysis

Question 16

C3 produces C4b and C3b which causes

Answer 16

opsonisation

Question 17

C3 also produces C3a and C5a which causes

Answer 17

inflammation–> binds to antigens on the cell and causes histamine release