Lumit® FcγR Binding Immunoassays

The Lumit® FcγR Binding Immunoassays are novel homogeneous (no-wash) competition assays to measure the interaction between human Fc receptors and antibodies or Fc fusion proteins. Lumit® Immunoassays are based on NanoBiT® complementation to generate a luminescent signal. In the assays, a human IgG1 labeled with LgBiT (Tracer-LgBiT) is used as the tracer. A C-terminal biotinylated human FcγR bound to Streptavidin-SmBiT (FcγR-Biotin-SA-SmBiT) is used as the target. In the absence of an antibody analyte sample, Tracer-LgBiT binds to the FcγR-SmBiT target, resulting in maximum luminescence signal. In analyte samples, unlabeled IgG will compete with Tracer-LgBiT for binding to the FcγR target, resulting in a concentration-dependent decrease in luminescent signal. These easy-to-use biochemical assays can complement and provide orthogonal data to support results from cell-based functional bioassays.

Fc receptors for IgG (FcγRs) are expressed by a variety of cells of hematopoietic origin and contribute to protective functions of the immune system. These receptors are so named because they possess affinity for the fragment-crystallizable (Fc) region of antibody molecules. Upon binding antibodies attached to diseased cells or pathogens, these receptors mediate effector functions such as antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). The various Fcγ receptors differ in their affinity for IgG subclasses, and these interactions are further modified by the IgG glycosylation pattern.