Question

Antibody can become a killer when it is bound with

• A. Cytokines
• B. Interleukins
• C. Chemokines
• D. Complement

Hint:

• Antibodies primarily neutralize or opsonize.
• Effector functions triggered by antigen-bound antibodies leading to killing:
  • Complement Activation (Classical Pathway) Leads to MAC formation and cell lysis.
  • Antibody-Dependent Cell-mediated Cytotoxicity (ADCC) NK cells, eosinophils, macrophages kill antibody-coated target cells.

Answer 1

The Correct Option is D

In the context of immunology, antibodies play a crucial role in the immune response by identifying and neutralizing foreign objects such as bacteria and viruses. However, they can also act as effectors, becoming "killers" when they are bound to specific components. The interaction of antibodies with the complement system is one such mechanism.

The complement system consists of a series of proteins that circulate in the blood in an inactive form. When antibodies bind to a pathogen surface, they can initiate the classical pathway of complement activation. This binding causes a cascade of reactions that lead to:

• Opsonization: Coating of the pathogen to enhance phagocytosis.
• Formation of the Membrane Attack Complex (MAC): This complex can directly lyse (break down) the pathogen by forming pores in its cell membrane.
• Inflammatory Response: Attracts immune cells to the site of infection and facilitates their attack on the pathogen.

Thus, when antibodies are bound with complement, they can effectively become killers by directly targeting and destroying pathogens. The correct answer to the question of how an antibody can become a killer is through its association with the Complement system.