What role do complement anaphylatoxins play in immune response?

Complement anaphylatoxins, such as C3a, C4a, and C5a, play a crucial role in the immune response primarily by attracting immune cells to the site of infection. These small peptides are generated during the activation of the complement system, which is part of the innate immune response. When pathogens invade, the complement system is activated, and anaphylatoxins are released as a result.

These anaphylatoxins have chemotactic properties, meaning they can attract neutrophils, macrophages, and other immune cells to the area of infection or inflammation. This recruitment enhances the immune response, as these cells are essential for phagocytosing pathogens, producing pro-inflammatory cytokines, and orchestrating further immune reactions.

While the complement system also plays roles in neutralizing bacterial toxins and enhancing phagocytosis, the specific function of anaphylatoxins focuses on cell attraction. They do not cause direct lysis of pathogens themselves; that function is attributed to the formation of the membrane attack complex (MAC) from other complement components. Thus, the correct understanding of anaphylatoxins emphasizes their role in facilitating an effective immune response through attracting immune cells.