Antibody-dependent cell-mediated cytotoxicity (ADCC) is an immune defense mechanism involving an effector cell lysing a target cell on which antibodies have bound to specific antigens on the target cell membrane.

The typical ADCC involves activation of natural killer (NK) cells by antibodies. NK cells express Fc receptors, mostly CD16 or FcγRIIIa (CD16a), on its cell surface. These Fc receptors recognize and bind to the Fc portion of an antibody, such as IgG, which has bound to the surface of a pathogen-infected target cell. Once the Fc receptor binds to the Fc region of IgG, the Natural Killer cell releases cytokines such as IFN-γ and cytotoxic molecules that attack the pathogen-infected target cell.

The human FcγRIIIa displays a dimorphism in the position of residue 158. One allele (V158) encodes a higher Fc affinity receptor variant with a valine at amino acid residue 158, and the other (F158) encodes a lower Fc affinity receptor variant having a phenylalanine at amino acid residue 158.

Recombinant Jurkat T cell expressing firefly luciferase gene under the control of NFAT response elements with constitutive expression of human FcγRIIIa, low affinity (F158) variant and Fcγ chain.

Figure 2.Recombinant Jurkat T cell expressing firefly luciferase gene under the control of NFAT response elements with constitutive expression of human FcγRIIIa, low affinity (F158) variant and Fcγ chain.

Figure 3. Dose response of CD20 Ab in ADCC Bioassay Effector Cell (Low Affinity/NFAT-Jurkat cells).