What effect does the complement system have on cells?

What effect does the complement system have on cells?

• A. Inhibits phagocytosis
• B. Lyses cells and signals phagocytes to remove them
• C. Stimulates cell division
• D. Neutralizes bacterial toxins

Answer: (B)

The complement system acts on target cells by two main actions: it can directly lyse cells through the membrane attack complex, creating pores in the cell membrane and leading to cell death; and it marks surfaces with opsonins like C3b that tag cells for easier recognition and uptake by phagocytes. This combination—opening holes in the membrane to destroy cells and signaling/opsonizing to recruit and instruct phagocytes to remove them—fits the described effect of the complement system on cells.

The complement system acts on target cells by two main actions: it can directly lyse cells through the membrane attack complex, creating pores in the cell membrane and leading to cell death; and it marks surfaces with opsonins like C3b that tag cells for easier recognition and uptake by phagocytes. This combination—opening holes in the membrane to destroy cells and signaling/opsonizing to recruit and instruct phagocytes to remove them—fits the described effect of the complement system on cells.