ADCC Assays

Antibody-mediated cytotoxicity assays ADCC) is a prominent mechanism in the host immune defense where the Fab region of an antibody binds to a specific antigen on a target cell (see figure below), commonly an infected cell or pathogen. The Fc region of the same antibody then binds to a FcγRIII or CD16 receptor on an effector cell, commonly a natural killer (NK) cell. The bound NK cell then secretes apoptosis-inducing agents, thus destroying the target cell.

adcc

The current gold standard target labeling species for ADCC is the stable isotope Chromium-51 (51Cr). The isotope is pre-loaded into the target cells prior to performing the assay. When lysed, the 51Crloaded target cells release 51Cr into the supernatant; the measured radioactivity in the supernatant indicates the extent of cell lysis. Radioactive assays such as these pose obvious safety threats and waste disposal concerns. The labeling procedure can also be arduous and time consuming. Additionally, artifacts from the labeling process and chromate ion toxicity are possible.

Recently developed cell-based methods, such as those outlined in the list application notes below, bypass the need for radioisotope-labeled cells, and rely instead on measurement of molecules released by lysed target cells, or measurement of binding of antibodies to target or FcγRIII receptors. The assays discussed here each have their own strengths, and are chosen depending on the lab’s needs and drug development research stage. When automated for medium- and high throughput, these new assays create simple, robust processes that require less active labor and increased consistency over time and with multiple users.

Application Notes

 

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