Fig 1: Antibody-dependent cell-mediated cytotoxicity (ADCC)

ADCC is a simple but important mechanism for the immune system to target diseased or infected cells. Antibodies bind to specific antigens on the surface of the target cell (see Fig 1).  PBMCs or natural killer (NK) cells, express Fc receptors on their cell surface and act as the effector cells. Interaction between the Fc region of the antibody and the Fc receptor induces the effector cell to degranulate, releasing IFN-γ, granzymes, and other cytotoxic compounds that lyse the target cell.

ADCC is not only a natural part of the adaptive immune response, but animal experiments have shown that it can also be seen as an important mechanism of action of therapeutic monoclonal antibodies (1), including the breast cancer drug trastuzumab, and rituximab, a drug used to treat diseases which show overactive, dysfunctional, or excessive numbers of B cells (e.g. lymphomas).

Cell lines to build up cellular ADCC screening assays

Fig 2: Principle of BPS’s ADCC cell lines

To enable researchers to build up a cellular ADCC screening system, BPS Biosciences have developed 2 reporter cell lines, which can replace NK cells or PBMCs in such a cellular assay (see Fig 2). The system is based on Jurkat cells that stably express human FcγRIIIa (CD16a), the receptor for the Fc region of human IgG. The FcγRIIIa on the Jurkat cells binds to the IgG on the surface of the target cell. This crosslinking causes the Jurkat cells to activate NFAT transcription, which induces the expression of luciferase and can be easily detected using the ONE-Step™ Luciferase Detection Reagents.

The effectiveness of ADCC depends on how well the effector cells are activated after the engagement of FcγRIIIa. Human FcγRIIIa displays dimorphism at amino acid 158 – one allele (V158) encodes a high Fc affinity receptor variant, while the other (F158) encodes a lower Fc affinity receptor variant.  BPS offers 2 different ADCC cell lines expressing either of these Fc receptors to allow selective antibody binding analyses using each type of receptor.

• ADCC Bioassay Effector Cell, F variant (Low Affinity)
• ADCC Bioassay Effector Cell V variant (High Affinity)

Get more information about our ADCC cell lines – just leave your questions or comments in the form below!

Reference:

(1) Clynes, RA, Towers, TL, Presta, LG, Ravetch, JV; Inhibitory Fc receptors modulate in vivo cytotoxicity against tumor targets; Nat Med. 6 (4): 443-446 (2000)

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Fig 1: CD39 and CD73 leading to elevated levels of extracellular adenosine.

Extracellular adenosine 5′-triphosphate (ATP) is released by dying and damaged cells, and it acts on many immune cells to promote inflammation. On the other hand, the unphosphorylated
metabolite, adenosine, functions as an anti-inflammatory molecule. Two extracellular ecto-5´-Nucleotidases, CD39, and CD73, convert extracellular ATP to ADP/AMP and AMP to adenosine, respectively, leading to elevated levels of extracellular adenosine (Fig 1).

There is an increasing demand for new cholesterol-lowering therapies in addition to existing treatments (e.g. targeting statins). The pharmacological inhibition of PCSK9-mediated LDLR degradation is becoming very attractive for treating cholesterol-related diseases. But which reliable in vitro assays are available to effectively study “PCSK9-LDLR” interactions ?

Fig 1: TIGIT (VSTM3)/CD226 and CD28/CTLA-4 Pathway

Over the past months, we have released a number of posts introducing inhibitor screening assays intended to investigate immuno checkpoint protein interactions, such as PD-1/PD-L1/PD-L2;  B7-1/CD28, B7-1/CTLA4;  BLTA/HVEM, CD47/SIRPα; GITR/GITRL and many others – for an overview, you might like to read 9 pathway-specific screening assays in Immunotherapy.

Today, I’d like to concentrate on the TIGIT/CD226 pathway, because it acts through a novel mechanism to regulate CD8+ T cell functions within the tumour microenvironment.