Antibody-dependent cell-mediated cytotoxicity (ADCC)

Definition

Antibody-dependent cell-mediated cytotoxicity (ADCC) is an immune response where antibodies bind to target cells, marking them for destruction by immune cells such as natural killer (NK) cells and macrophages. This process highlights the interaction between the adaptive immune system, through antibodies, and innate immune cells, allowing for the targeted elimination of infected or cancerous cells.

5 Must Know Facts For Your Next Test

1. ADCC is mediated by the binding of the Fc region of antibodies to Fc receptors on effector cells like NK cells and macrophages.
2. This mechanism plays a significant role in controlling viral infections and targeting tumor cells for destruction.
3. ADCC can enhance the effectiveness of certain therapeutic monoclonal antibodies used in cancer treatment by recruiting immune effector cells.
4. The efficiency of ADCC can vary based on the type of antibody and the expression levels of Fc receptors on the effector cells.
5. In some cases, evasion mechanisms employed by tumors can reduce the effectiveness of ADCC, highlighting its complexity in cancer immunotherapy.

Review Questions

• How does ADCC facilitate the destruction of target cells by immune effector cells?
  • ADCC facilitates cell destruction by using antibodies to mark target cells for recognition by immune effector cells. When antibodies bind to antigens on infected or malignant cells, they expose their Fc regions, which are recognized by Fc receptors on NK cells and macrophages. This interaction triggers these effector cells to release cytotoxic substances that lead to apoptosis or lysis of the target cell, effectively clearing the threat from the body.
• Discuss the role of monoclonal antibodies in enhancing ADCC in cancer therapies.
  • Monoclonal antibodies play a pivotal role in enhancing ADCC by specifically targeting antigens expressed on cancer cells. When these antibodies bind to their targets, they not only inhibit tumor growth but also recruit immune effector cells through their Fc regions. This recruitment leads to increased ADCC activity, where NK cells and other immune cells are activated to kill the antibody-coated cancer cells. Such strategies have shown promising results in improving patient outcomes in various cancers.
• Evaluate how factors such as Fc receptor expression levels influence the efficacy of ADCC in different contexts.
  • The efficacy of ADCC is significantly influenced by factors such as the density and affinity of Fc receptors expressed on immune effector cells. High expression levels can enhance the binding efficiency and subsequent activation of NK cells and macrophages leading to more effective target cell elimination. Conversely, tumors may develop mechanisms to downregulate these receptors or express inhibitory ligands that can dampen ADCC activity. Understanding these dynamics is crucial for developing effective immunotherapeutic strategies that utilize ADCC to combat cancers or chronic infections.

Related terms

Natural Killer (NK) Cells: A type of lymphocyte that plays a crucial role in the innate immune system, NK cells can recognize and destroy virus-infected or tumor cells without prior sensitization.

Monoclonal Antibodies: Laboratory-made molecules engineered to bind to specific targets on cells, often used in therapies to stimulate ADCC against cancer cells.

Cytotoxic T Lymphocytes (CTLs): A subtype of T cells that directly kill infected or cancerous cells, CTLs are another important part of the adaptive immune response that can also work alongside ADCC.