Classical, alternative, and lectin complement pathways and the deficiency disorders tied to each component tested on USMLE Step 1.
29 cards · basic cards · AI-written, checked twice. Edit anything.
- Which complement protein is the first to be activated in the classical pathway?
- C1q
- What directly triggers activation of the classical complement pathway?
- Antigen-antibody (immune) complexes binding C1q
- Which antibody isotype is the most efficient activator of the classical complement pathway?
- IgM
- IgM is a more efficient activator of the classical complement pathway than IgG because IgM's ____ structure can bind multiple C1q heads at once.
- pentameric
- What is the C3 convertase of the classical pathway?
- C4b2a
- What triggers activation of the lectin complement pathway?
- Mannose-binding lectin (MBL) binding mannose residues on a pathogen surface
- Which enzymes does mannose-binding lectin activate to drive the lectin pathway?
- MASPs (MBL-associated serine proteases)
- What triggers activation of the alternative complement pathway?
- Spontaneous hydrolysis of C3 on a microbial surface, without antibody
- What is the C3 convertase of the alternative pathway?
- C3bBb
- Which protein stabilizes the alternative pathway's C3 convertase?
- Properdin (factor P)
- Which protein binds C3b and is then cleaved by factor D in the alternative pathway?
- Factor B
- What is the C5 convertase formed by the classical and lectin pathways?
- C4b2a3b
- What is the C5 convertase formed by the alternative pathway?
- C3bBb3b
- Which complement proteins make up the membrane attack complex?
- C5b-9
- What is the main function of the membrane attack complex?
- It lyses the pathogen cell membrane, especially gram-negative bacteria like Neisseria