Which statement distinguishes CRP action from antibody action?

Which statement distinguishes CRP action from antibody action?

• A. CRP acts before the antibody appears.
• B. Only the antibody triggers the complement cascade.
• C. Binding of the antibody is calcium-dependent.
• D. Only CRP acts as an opsonin.

Answer: (A)

CRP is an acute-phase protein that rises rapidly during inflammation and can act in innate immunity before the adaptive response has produced antibodies. It binds to microbial surfaces and damaged cells and activates the classical complement pathway by interacting with C1q, promoting opsonization and clearance even in the absence of specific antibodies. Antibodies, part of the adaptive response, appear later after antigen exposure and can also activate complement and promote phagocytosis, but their action requires prior antigen-specific activation. The statement that CRP acts before the antibody appears captures this timing difference and innate-immune readiness. The idea that only antibodies trigger complement is incorrect because CRP can initiate complement activation on its own. The notion that antibody binding is calcium-dependent isn’t correct, since antigen–antibody interactions don’t require calcium. And saying only CRP acts as an opsonin isn’t right, because antibodies can also function as opsonins through Fc receptor interactions on phagocytes.

CRP is an acute-phase protein that rises rapidly during inflammation and can act in innate immunity before the adaptive response has produced antibodies. It binds to microbial surfaces and damaged cells and activates the classical complement pathway by interacting with C1q, promoting opsonization and clearance even in the absence of specific antibodies. Antibodies, part of the adaptive response, appear later after antigen exposure and can also activate complement and promote phagocytosis, but their action requires prior antigen-specific activation.

The statement that CRP acts before the antibody appears captures this timing difference and innate-immune readiness. The idea that only antibodies trigger complement is incorrect because CRP can initiate complement activation on its own. The notion that antibody binding is calcium-dependent isn’t correct, since antigen–antibody interactions don’t require calcium. And saying only CRP acts as an opsonin isn’t right, because antibodies can also function as opsonins through Fc receptor interactions on phagocytes.