Antibody-Dependent Cell-Mediated Cytotoxicity

Definition

Antibody-dependent cell-mediated cytotoxicity (ADCC) is an immune response mechanism in which antibodies bound to the surface of a target cell stimulate effector cells, such as natural killer (NK) cells, to destroy that target cell. This process is a key component of the humoral immune response and plays a crucial role in the context of hypersensitivity reactions.

5 Must Know Facts For Your Next Test

1. ADCC is a key mechanism in the body's defense against viral infections, cancer cells, and antibody-coated pathogens.
2. The process involves antibodies binding to the surface of a target cell, which then crosslink with Fc receptors on effector cells, triggering the release of cytotoxic granules and the destruction of the target cell.
3. Effector cells involved in ADCC include natural killer (NK) cells, monocytes, macrophages, and eosinophils.
4. ADCC is particularly important in the context of type II hypersensitivity reactions, where antibodies bind to self-antigens on the surface of cells, leading to their destruction by effector cells.
5. The efficiency of ADCC can be influenced by factors such as antibody isotype, Fc receptor expression on effector cells, and the availability of target antigens on the cell surface.

Review Questions

• Explain the role of antibody-dependent cell-mediated cytotoxicity (ADCC) in the body's defense against viral infections and cancer cells.
  • Antibody-dependent cell-mediated cytotoxicity (ADCC) is a crucial immune response mechanism that helps the body defend against viral infections and cancer cells. In ADCC, antibodies bind to the surface of target cells, such as virus-infected cells or cancer cells, and then crosslink with Fc receptors on effector cells like natural killer (NK) cells. This triggering of the effector cells leads to the release of cytotoxic granules, which ultimately destroy the target cell. ADCC is particularly effective against viruses and cancer cells because it allows the immune system to recognize and eliminate these threats, even when the target cells may have mechanisms to evade other immune responses.
• Describe how antibody-dependent cell-mediated cytotoxicity (ADCC) is involved in type II hypersensitivity reactions.
  • In type II hypersensitivity reactions, antibodies bind to self-antigens on the surface of the body's own cells, leading to their destruction through the process of antibody-dependent cell-mediated cytotoxicity (ADCC). In this scenario, the antibodies act as a bridge, connecting the target cells to effector cells like natural killer (NK) cells or macrophages. The crosslinking of Fc receptors on the effector cells triggers the release of cytotoxic granules, which then induce apoptosis or lysis of the target cells. This inappropriate immune response against the body's own cells can result in tissue damage and the clinical symptoms associated with type II hypersensitivity reactions.
• Analyze how factors such as antibody isotype, Fc receptor expression, and target antigen availability can influence the efficiency of antibody-dependent cell-mediated cytotoxicity (ADCC).
  • The efficiency of antibody-dependent cell-mediated cytotoxicity (ADCC) can be influenced by several key factors. The antibody isotype is important, as different isotypes (e.g., IgG, IgA) have varying affinities for Fc receptors on effector cells, which can impact the strength of the ADCC response. The expression levels of Fc receptors on the surface of effector cells, such as natural killer (NK) cells and macrophages, can also affect the potency of the ADCC reaction, as more receptors available means a stronger activation signal. Additionally, the availability and density of target antigens on the surface of the target cell can influence the ability of antibodies to bind and effectively crosslink Fc receptors, thereby modulating the overall efficiency of the ADCC process. Understanding how these factors interplay is crucial for understanding the context-dependent nature of ADCC and its role in immune responses and hypersensitivity reactions.

Related terms

Effector Cells: Cells of the immune system, such as natural killer (NK) cells, that are responsible for directly killing or neutralizing target cells or pathogens.

Humoral Immune Response: The branch of the adaptive immune system that involves the production of antibodies by B cells to recognize and neutralize extracellular pathogens and toxins.

Hypersensitivity:

An exaggerated or inappropriate immune response to an antigen, leading to tissue damage or clinical symptoms.