Final answer:
Antibody-dependent cell-mediated cytotoxicity (ADCC) involves the binding of an antibody's Fab region to a pathogen and its Fc region to an effector cell's Fc receptor, leading to the release of cytotoxins like perforin and granzymes to kill the pathogen. ADCC is also significant in type II hypersensitivities and therapeutic applications, such as targeting tumor cells in cancer treatment.
Step-by-step explanation:
Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC):
Antibody-dependent cell-mediated cytotoxicity (ADCC) is a crucial immune defense mechanism, particularly against pathogens that are too large for phagocytosis. ADCC involves the binding of the Fab region of an IgG antibody to a pathogen, and the subsequent attachment of the Fc region of the antibody to Fc receptors on effector cells, such as natural killer (NK) cells. This close proximity allows the effector cell to release cytotoxic substances like perforin and granzymes, which ultimately lead to the destruction of the pathogen. Additionally, macrophages, eosinophils, and neutrophils can also participate in ADCC by binding their Fc receptors to antibodies on the target cell contributing to cell lysis. Aside from its involvement in pathogen clearance, ADCC is also significant in the context of hypersensitivity, especially type II cytotoxic hypersensitivities.
Here antibodies (typically IgG and IgM) bind to cell-surface antigens, which may result in two pathways: the initiation of complement activation, causing inflammation and lysis, or the facilitation of ADCC to induce cell death. The significance of ADCC extends into therapeutic applications, for example in cancer treatment, where monoclonal antibodies can be designed to target tumor cells and recruit the immune system to attack these cells via ADCC. Understanding the mechanism of ADCC is thus fundamental to advancing both our comprehension and manipulation of immune responses.