Antibody-dependent cell-mediated cytotoxicity

Definition

Antibody-dependent cell-mediated cytotoxicity (ADCC) is an immune response mechanism where antibodies bound to a target cell, such as an infected or tumor cell, facilitate the destruction of that cell by immune effector cells like natural killer (NK) cells or macrophages. This process relies on the specific recognition of the antibody-bound target by Fc receptors on effector cells, leading to the activation of these immune cells and the release of cytotoxic substances to kill the target cell.

5 Must Know Facts For Your Next Test

1. ADCC is crucial for eliminating cells infected with viruses, as well as cancerous cells that present abnormal antigens.
2. The effectiveness of ADCC can be influenced by the subclass of antibodies involved; for example, IgG1 and IgG3 subclasses are particularly efficient at triggering this response.
3. ADCC is distinct from complement-mediated lysis, though both can occur simultaneously against the same target cell.
4. Therapeutic monoclonal antibodies are often designed to enhance ADCC, making them more effective in treating cancers and autoimmune diseases.
5. Factors such as the density of antigens on target cells and the affinity of antibodies can significantly impact the efficiency of ADCC.

Review Questions

• How do antibodies facilitate the process of antibody-dependent cell-mediated cytotoxicity, and what role do immune effector cells play in this mechanism?
  • Antibodies facilitate ADCC by binding to specific antigens on target cells, such as those infected with viruses or malignant cells. Once bound, the Fc region of the antibodies interacts with Fc receptors on immune effector cells like NK cells or macrophages. This interaction triggers signaling pathways that lead to the activation of these effector cells, allowing them to release cytotoxic substances that kill the antibody-coated target cell.
• Discuss how therapeutic monoclonal antibodies utilize antibody-dependent cell-mediated cytotoxicity to improve treatment outcomes for cancer patients.
  • Therapeutic monoclonal antibodies are engineered to specifically bind to cancer cell antigens. By binding to these targets, they mark the cancerous cells for destruction. The bound antibodies then engage effector immune cells through their Fc regions, activating ADCC. This process enhances the overall anti-tumor response by promoting targeted killing of malignant cells while minimizing damage to healthy tissues.
• Evaluate the factors that can affect the efficiency of antibody-dependent cell-mediated cytotoxicity and their implications for immunotherapy.
  • The efficiency of ADCC can be influenced by several factors including antibody subclass, antigen density on target cells, and the presence of various immune suppressive factors in the tumor microenvironment. For instance, higher antigen density can enhance binding and subsequent cytotoxicity by effector cells. In immunotherapy contexts, optimizing these factors is essential for maximizing treatment efficacy, as a robust ADCC response can significantly improve patient outcomes in diseases such as cancer.

Related terms

Natural Killer (NK) Cells: A type of lymphocyte that plays a critical role in the innate immune system, specifically targeting and destroying virus-infected cells and tumor cells.

Monoclonal Antibodies: Antibodies produced from a single clone of B cells, designed to bind to specific antigens; they are used in therapies to target specific cells for destruction.

Fc Receptors: Proteins found on the surface of certain immune cells that bind to the Fc region of antibodies, crucial for mediating various immune responses including ADCC.