Which best describes the role of an anaphylatoxin?

Which best describes the role of an anaphylatoxin?

• A. Increases permeability of blood vessels
• B. Coats cells to increase phagocytosis
• C. Attracts WBCs to the area of antigen concentration
• D. Increases production of interleukin-1

Answer: (A)

Anaphylatoxins are small fragments generated during complement activation that drive inflammation by making local blood vessels leakier. They stimulate mast cells and basophils to release histamine and other mediators, which increases vascular permeability. This leakage allows plasma proteins and leukocytes to exit into the tissue, producing edema and helping immune components reach the site of antigen quickly. While these fragments can also recruit white blood cells to the area (a chemotactic effect, especially for some components), the defining action most closely associated with anaphylatoxins is the rapid increase in vascular permeability. They are not primarily responsible for coating microbes to boost phagocytosis—that’s the job of opsonins like C3b—and they do not directly induce IL-1 production, which comes from cytokine signaling in inflammation.

Anaphylatoxins are small fragments generated during complement activation that drive inflammation by making local blood vessels leakier. They stimulate mast cells and basophils to release histamine and other mediators, which increases vascular permeability. This leakage allows plasma proteins and leukocytes to exit into the tissue, producing edema and helping immune components reach the site of antigen quickly. While these fragments can also recruit white blood cells to the area (a chemotactic effect, especially for some components), the defining action most closely associated with anaphylatoxins is the rapid increase in vascular permeability. They are not primarily responsible for coating microbes to boost phagocytosis—that’s the job of opsonins like C3b—and they do not directly induce IL-1 production, which comes from cytokine signaling in inflammation.