Antibody-dependent cellular cytotoxicity
Encyclopedia
Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC) is a mechanism of cell-mediated immunity whereby an effector cell of the immune system
actively lyses
a target cell that has been bound by specific antibodies. It is one of the mechanisms through which antibodies, as part of the humoral immune response
, can act to limit and contain infection. Classical ADCC is mediated by natural killer (NK) cells
; neutrophils and eosinophils can also mediate ADCC. For example, eosinophils can kill certain parasitic worms known as helminths through ADCC. ADCC is part of the adaptive immune response
due to its dependence on a prior antibody response.
, such as IgG, which has bound to the surface of a pathogen
-infected target cell. The most common Fc receptor on the surface of an NK Cell is called CD16
or FcγRIII. Once the Fc receptor binds to the Fc region of IgG, the Natural Killer cell releases cytokines such as IFN-γ, and cytotoxic granules containing perforin
and granzymes that enter the target cell and promote cell death by triggering apoptosis
. This is similar to, but independent of, responses by cytotoxic T cell
s (CTLs).
s. However, an antibody called IgE
can coat these parasites. The Fc receptor
(FceRI) of an eosinophil can then recognize IgE. The interaction between FceRI and the Fc portion of helminth-bound IgE causes the eosinophil to degranulate.
[Eu] release assay, and sulfur-35 [S35] release assay. Usually, a labelled target cell line expressing a certain surface-exposed antigen
is incubated with antibody specific for that antigen. After washing, effector cells expressing Fc receptor CD16 are co-incubated with the antibody-labelled target cells. Target cell lysis is subsequently measured by release of intracellular label by a scintillation counter or spectrophotometry.
A common challenge faced by ADCC assays is high background signaling due to cellular "leakiness". While both Cr51 and Eu-based assays face this challenge, S35-containing methionine
and cysteine
pre-incubated with target cells leads to incorporation of radio-labelled molecules into newly translated peptides.
The coupled bioluminescent method aCella TOXTM is now in widespread use for ADCC and other cytotoxicity assessments. Since this technique measures the release of enzymes naturally present in the target cells, no labeling step is required and no radioactive agents are used.
, including trastuzumab
and rituximab
, against tumors.
In the clinic the FcgRIII 158V/F polymorphism interfere with the ability to generate ADCC responses in vitro during trastuzumab treatment.
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
actively lyses
Lysis
Lysis refers to the breaking down of a cell, often by viral, enzymic, or osmotic mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a "lysate"....
a target cell that has been bound by specific antibodies. It is one of the mechanisms through which antibodies, as part of the humoral immune response
Humoral immunity
The Humoral Immune Response is the aspect of immunity that is mediated by secreted antibodies produced in the cells of the B lymphocyte lineage . B Cells transform into plasma cells which secrete antibodies...
, can act to limit and contain infection. Classical ADCC is mediated by natural killer (NK) cells
Natural killer cell
Natural killer cells are a type of cytotoxic lymphocyte that constitute a major component of the innate immune system. NK cells play a major role in the rejection of tumors and cells infected by viruses...
; neutrophils and eosinophils can also mediate ADCC. For example, eosinophils can kill certain parasitic worms known as helminths through ADCC. ADCC is part of the adaptive immune response
Adaptive immune system
The adaptive immune system is composed of highly specialized, systemic cells and processes that eliminate or prevent pathogenic growth. Thought to have arisen in the first jawed vertebrates, the adaptive or "specific" immune system is activated by the “non-specific” and evolutionarily older innate...
due to its dependence on a prior antibody response.
ADCC by NK cells
The typical ADCC involves activation of NK cells by antibodies. An NK cell express CD16 which is a Fc receptor recognizes the Fc portion of an antibodyAntibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
, such as IgG, which has bound to the surface of a pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
-infected target cell. The most common Fc receptor on the surface of an NK Cell is called CD16
CD16
CD16 is a low affinity Fc receptor.It is a cluster of differentiation found on the surface of natural killer cells, neutrophil polymorphonuclear leukocytes, monocytes and macrophages...
or FcγRIII. Once the Fc receptor binds to the Fc region of IgG, the Natural Killer cell releases cytokines such as IFN-γ, and cytotoxic granules containing perforin
Perforin
Perforin-1 is a protein that in humans is encoded by the PRF1 gene.- Function :Perforin is a cytolytic protein found in the granules of CD8 T-cells and NK cells. Upon degranulation, perforin inserts itself into the target cell's plasma membrane, forming a pore. The lytic membrane-inserting part...
and granzymes that enter the target cell and promote cell death by triggering apoptosis
Apoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
. This is similar to, but independent of, responses by cytotoxic T cell
Cytotoxic T cell
A cytotoxic T cell belongs to a sub-group of T lymphocytes that are capable of inducing the death of infected somatic or tumor cells; they kill cells that are infected with viruses , or are otherwise damaged or...
s (CTLs).
ADCC by eosinophils
Large parasites like helminths are too big to be engulfed and killed by phagocytosis. They also have an external structure or integument that is resistant to attack by substances released by neutrophils and macrophageMacrophage
Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...
s. However, an antibody called IgE
IGE
IGE was one of the largest services company buying and selling virtual currencies and accounts for MMORPG. During its peak time, it had offices in Los Angeles, China , and headquarters & customer service centre in Hong Kong. IGE was one of the main monopoly in virtual economy services, also known...
can coat these parasites. The Fc receptor
Fc receptor
An Fc receptor is a protein found on the surface of certain cells - including natural killer cells, macrophages, neutrophils, and mast cells - that contribute to the protective functions of the immune system....
(FceRI) of an eosinophil can then recognize IgE. The interaction between FceRI and the Fc portion of helminth-bound IgE causes the eosinophil to degranulate.
ADCC in vitro
Several laboratory methods exist for determining the efficacy of antibodies or effector cells in eliciting ADCC. Among these methods include chromium-51 [Cr51] release assay, europiumEuropium
Europium is a chemical element with the symbol Eu and atomic number 63. It is named after the continent of Europe. It is a moderately hard silvery metal which readily oxidizes in air and water...
[Eu] release assay, and sulfur-35 [S35] release assay. Usually, a labelled target cell line expressing a certain surface-exposed antigen
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
is incubated with antibody specific for that antigen. After washing, effector cells expressing Fc receptor CD16 are co-incubated with the antibody-labelled target cells. Target cell lysis is subsequently measured by release of intracellular label by a scintillation counter or spectrophotometry.
A common challenge faced by ADCC assays is high background signaling due to cellular "leakiness". While both Cr51 and Eu-based assays face this challenge, S35-containing methionine
Methionine
Methionine is an α-amino acid with the chemical formula HO2CCHCH2CH2SCH3. This essential amino acid is classified as nonpolar. This amino-acid is coded by the codon AUG, also known as the initiation codon, since it indicates mRNA's coding region where translation into protein...
and cysteine
Cysteine
Cysteine is an α-amino acid with the chemical formula HO2CCHCH2SH. It is a non-essential amino acid, which means that it is biosynthesized in humans. Its codons are UGU and UGC. The side chain on cysteine is thiol, which is polar and thus cysteine is usually classified as a hydrophilic amino acid...
pre-incubated with target cells leads to incorporation of radio-labelled molecules into newly translated peptides.
The coupled bioluminescent method aCella TOXTM is now in widespread use for ADCC and other cytotoxicity assessments. Since this technique measures the release of enzymes naturally present in the target cells, no labeling step is required and no radioactive agents are used.
Monoclonal antibody action against tumors
Experiments in mice indicate that ADCC is an important mechanism of action of therapeutic monoclonal antibodiesMonoclonal antibodies
Monoclonal antibodies are monospecific antibodies that are the same because they are made by identical immune cells that are all clones of a unique parent cell....
, including trastuzumab
Trastuzumab
Trastuzumab is a monoclonal antibody that interferes with the HER2/neu receptor.The HER receptors are proteins that are embedded in the cell membrane and communicate molecular signals from outside the cell to inside the cell, and turn genes on and off...
and rituximab
Rituximab
Rituximab, sold under the trade names Rituxan and MabThera, is a chimeric monoclonal antibody against the protein CD20, which is primarily found on the surface of B cells...
, against tumors.
In the clinic the FcgRIII 158V/F polymorphism interfere with the ability to generate ADCC responses in vitro during trastuzumab treatment.
External links
- University of Leicester, Virus Immunopathology Notes