Complement

Question 1

Biologic Functions of Complement

Answer 1

• Tags pathogens for phagocytosis (opsonization)
• Lysis of bacteria or viral pathogens
• Clearance of immune complexes
• Recruitment of inflammatory cells (mediated by anaphylatoxins)
• Enhancement of humoral (antibody mediated) response

Question 2

3 complement pathways

Answer 2

• Classical pathway
• Mannan binding lectin pathway
• Alternative pathway;

Each pathway is triggered differently but all 3 lead to C3 activation, the deposition of C3b on the pathogen surface

Question 3

Classical pathway

Answer 3

activated by binding of IgG or IgM antibody (or C-reactive protein) to pathogen surface.

Question 4

Mannan Binding Lectin Pathway

Answer 4

activated by the binding of mannose binding lectin (MBL) to mannose containing carbohydrates on viruses or bacteria.

Question 5

Alternative Pathway

Answer 5

activated by the spontaneous hydrolysis of C3 followed by direct binding of a complement split product (C3b) to a pathogen surface

Question 6

Complement Fixation

Answer 6

C1 binding to 2 Ab on Ag surface

Question 7

Active Split Products: Opsonins

Answer 7

c3b c4b

Question 8

Active Split Products: Anaphylatoxins

Answer 8

c3a c5a

Question 9

Active Split Products: Chemotactic for neutrophils

Answer 9

c5a