Question

The membrane attack complex (MAC) is characterized by all except:

A. MAC components are the same in the final common pathway of complement activation

B. C5-8 complex polymerizes C9 to form a tubule known as MAC

C. MAC allows for the influx of NA+ and H2O which produces lysis

D. The complement cascade reaches full amplitude at this stage

Answer 1

MAC components of C5-C9 form a ring structure leading to cell lysis; the incorrect statement is that MAC components are the same in the final common pathway, as the classical pathway requires an antigen-antibody complex.

Step-by-step explanation:

The membrane attack complex (MAC) is characterized by the formation of a ring structure that disrupts the cell membrane of the targeted pathogen, causing cell lysis and death. Except for one characteristic, all of the following statements are true about MAC:

• MAC components are the same in the final common pathway of complement activation.
• The C5-8 complex polymerizes C9 to form a tubule known as MAC.
• MAC allows for the influx of Na+ and H2O which produces lysis.
• The complement cascade reaches full amplitude at this stage.

The incorrect statement (which should be ignored) is 'MAC components are the same in the final common pathway of complement activation.' In both the classical and alternate pathways, C5-C9 form the MAC, but only the classical pathway requires an antigen-antibody complex for initiation.