🔅 What is the mechanism of antibody-dependent cell-mediated cytotoxicity (ADCC)?

– Antibody-dependent cell-mediated cytotoxicity (ADCC) is a mechanism of cell-mediated immune defense whereby an effector cell of the immune system kills a target cell that has been coated with specific antibodies.

– The main steps of ADCC are:

• First, antibodies bind to the antigens on the surface of the target cell, forming an antibody-antigen complex.

• Second, the effector cell, such as a natural killer (NK) cell, a macrophage, or an eosinophil, recognizes and binds to the Fc region of the antibody via its Fc receptor (FcR).

• Third, the cross-linking of FcRs by multiple antibody-antigen complexes triggers the activation and degranulation of the effector cell.

• Fourth, the effector cell releases cytotoxic molecules, such as perforin, granzymes, and cytokines, that damage or destroy the target cell.

– ADCC is an important mechanism for eliminating cells that are infected by viruses, bacteria, parasites, or fungi, as well as cells that are abnormal or malignant. ADCC is also involved in some allergic reactions and autoimmune diseases.

– ADCC can be enhanced by using monoclonal antibodies that have high affinity and specificity for certain antigens and FcRs. ADCC can also be modulated by factors such as the expression level and polymorphism of FcRs, the type and density of antigens, and the availability and concentration of antibodies.

What is the difference between ADCC and complement-dependent cytotoxicity (CDC)?

– The difference between ADCC and CDC is that ADCC is a mechanism of cell-mediated immune defense whereby an effector cell of the immune system kills a target cell that has been coated with specific antibodies, while CDC is a mechanism of humoral immune defense whereby the complement system lyses a target cell that has been coated with specific antibodies.

– ADCC and CDC have different requirements and outcomes. ADCC requires an effector cell, such as a natural killer (NK) cell, a macrophage, or an eosinophil, that expresses Fc receptors that can bind to the Fc region of the antibody.

– CDC requires the activation of the complement cascade, which involves a series of proteins that can bind to the antibody and form a membrane attack complex (MAC) on the target cell. ADCC results in the release of cytotoxic molecules, such as perforin, granzymes, and cytokines, that damage or destroy the target cell. CDC results in the formation of pores on the target cell membrane that cause osmotic lysis or inflammation.

– ADCC and CDC have different roles and applications in immunity and therapy. ADCC is more effective against cells that are infected by viruses, bacteria, parasites, or fungi, as well as cells that are abnormal or malignant. CDC is more effective against cells that have a high density of antigens and are sensitive to complement-mediated damage. ADCC and CDC can also work together to enhance the immune response against certain targets. ADCC and CDC can be used as mechanisms for antibody-based therapies against various diseases, such as cancer, autoimmune disorders, inflammatory diseases, and infectious diseases.

What is the role of Fc receptors in ADCC?

– The role of Fc receptors in ADCC is to recognize and bind to the Fc region of the antibody that is attached to the target cell, and to activate and degranulate the effector cell that can kill the target cell. Fc receptors are a family of receptors that are expressed on various immune cells, such as natural killer (NK) cells, macrophages, eosinophils, and neutrophils. Fc receptors can bind to different classes and subclasses of antibodies, such as IgG, IgA, IgE, and IgM. The binding of Fc receptors to antibodies is mediated by weak and noncovalent forces, such as hydrogen bonds, electrostatic interactions, van der Waals forces, and hydrophobic interactions. The strength and specificity of the binding depend on the shape, size, charge, and chemical composition of both the antibody and the Fc receptor.

– ADCC is an important mechanism for eliminating cells that are infected by viruses, bacteria, parasites, or fungi, as well as cells that are abnormal or malignant. ADCC is also involved in some allergic reactions and autoimmune diseases.

– ADCC can be enhanced by using monoclonal antibodies that have high affinity and specificity for certain antigens and FcRs. ADCC can also be modulated by factors such as the expression level and polymorphism of FcRs, the type and density of antigens, and the availability and concentration of antibodies.

I hope you found this information helpful and understandable and that you gained more about the role of Fc receptors in ADCC.