key term - Complement-dependent cytotoxicity

Definition

Complement-dependent cytotoxicity refers to a mechanism of immune response where the complement system is activated and leads to the destruction of target cells, usually through opsonization and formation of the membrane attack complex. This process plays a significant role in mediating antibody-dependent cell-mediated cytotoxicity and is crucial in the context of hypersensitivity reactions, particularly those classified as type II hypersensitivity.

5 Must Know Facts For Your Next Test

1. Complement-dependent cytotoxicity is primarily triggered when antibodies bind to antigens on the surface of target cells, activating the complement system.
2. This mechanism can lead to the formation of pores in the target cell membrane through the assembly of the membrane attack complex (MAC), resulting in cell lysis.
3. It is commonly seen in autoimmune diseases where the body produces antibodies against its own cells, leading to tissue damage.
4. In transfusion reactions, complement-dependent cytotoxicity plays a key role when mismatched blood types cause destruction of red blood cells.
5. Therapeutic monoclonal antibodies can harness complement-dependent cytotoxicity to selectively target and destroy cancer cells.

Review Questions

• How does complement-dependent cytotoxicity contribute to type II hypersensitivity reactions?
  • In type II hypersensitivity reactions, complement-dependent cytotoxicity occurs when antibodies bind to specific antigens present on target cells, such as red blood cells. This binding activates the complement system, which then leads to opsonization of these cells and promotes their destruction through mechanisms like cell lysis. The result is tissue damage and inflammation as the immune system mistakenly targets its own cells.
• Evaluate the implications of using therapeutic monoclonal antibodies that induce complement-dependent cytotoxicity in treating cancer.
  • Therapeutic monoclonal antibodies that induce complement-dependent cytotoxicity can selectively target cancer cells by binding to specific tumor antigens. This binding activates the complement system, promoting cell lysis and enhancing the anti-tumor immune response. However, while these therapies can effectively eliminate cancer cells, they also carry risks such as potential damage to healthy tissues expressing similar antigens and triggering systemic inflammatory responses.
• Assess the role of complement-dependent cytotoxicity in autoimmune diseases and how it leads to tissue damage.
  • In autoimmune diseases, the body produces antibodies against its own cells or tissues, leading to complement-dependent cytotoxicity. These autoantibodies bind to self-antigens, activating the complement system, which results in opsonization and eventual lysis of affected cells. This process contributes to tissue damage and inflammation, exacerbating the disease and highlighting a misdirected immune response that harms rather than protects the body.

Related terms

Complement System: A group of proteins that play an essential role in the immune response by promoting inflammation, opsonization, and cell lysis.

Opsonization:

The process by which pathogens are marked for destruction by immune cells, enhancing their recognition and ingestion by phagocytes.

Type II Hypersensitivity:

An allergic reaction that involves the production of antibodies against specific antigens on cell surfaces, leading to complement activation and cell damage.