Antibody-dependent cell-mediated cytotoxicity ADCC

Large granular lymphocytes, not belonging to either the T- or B-cell lineage. Natural killer (NK) cells are considered part of the innate defense system since, in contrast to cytotoxic T-cells, they are able to kill certain tumor cells in vitro without prior sensitization. The basal activity of NIC cells increases dramatically following stimulation with type I IFNs. In addition, NK cells display Fc-receptors for IgG and are important mediators of Antibody-Dependent-Cell-mediated-Cytotoxicity (ADCC). 

NK cells possess a receptor for Fc/and this enables them to adhere to target cells coated in antibody with the resultant destruction ofthat cell. This phenomenon is known as antibody-dependent cell-mediated cytotoxicity (ADCC). This was attributed to a separate cell population known as killer (K) cells but these have now been shown to be in effect NK cells. 

IgG Immunoglobulin G is present in lymph fluid, blood, cerebrospinal fluid and peritoneal fluid. It is composed of 2 y chains of 50 kDa and 2 L chains (k or ) of 25 kDa with a total molecular weight of 150 kDa. The functions of IgG include agglutination and formation of precipitate, passage through placenta and thus conferring immunity to fetus, opsonization, antibody-dependent cell-mediated cytotoxicity (ADCC), activation of complement, neutralization of toxins, immobilization of bacteria and neutralization of virus. 

In humans, there are five isotypes of antibodies, IgG, IgA, IgD, IgE, and IgM, which are defined by the structures of their heavy chains and their abilities to form multimers (Figure 10.1) [8], IgG is the most abundant isotype present in serum with average serum concentrations ranging from 0.5 to 9mg/ml depending on the IgG subtype. This is followed by IgA (3mg/ml), IgM (1.5mg/ml), IgE (0.05 mg/ml), and IgD (trace). Each antibody isotype has unique functions. Critical functions of IgG include opsonization, complement activation, antibody-dependent cell-mediated cytotoxicity (ADCC), passive immunity, and regulation of B cells. Both IgM and IgD act as antigen receptors on naive B cells, and soluble, multimeric forms of IgM are involved in complement activation. IgA is involved in mucosal and passive neonatal immunity, while IgE is involved in immediate hypersensitivity [8],... 

Antibody-dependent cell-mediated cytotoxicity (ADCC). 

Null cells Antibody-dependent cell-mediated cytotoxicity (ADCC) involving non-T/non-B cells (null cells) with F, receptors specific for antibody-coated target cells. 

K-cells in this reaction, termed antibody-dependent cell mediated cytotoxicity (ADCC), Conversely humoral antibody may combine with tumor antigens shed at the cell surface to act as "blocking factors to inhibit ADCC,... 

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