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Fc receptor definition

Fc receptor is a antibody receptor involved in antigen recognition which is located at the membrane of certain immune cells including B lymphocytes, natural killer cells, macrophages, neutrophils, and mast cells. Such receptors recognize Fc fragment of antibodies and that is the name of Fc receptor derived from. Fc receptors binding to antibodies that are attached to infected cells or invading pathogens contributes to the protective functions of the immune system.Their activity stimulates phagocytic or cytotoxic cells to destroy microbes, or infected cells by antibody-mediated phagocytosis or antibody-dependent cell-mediated cytotoxicity.

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There’s some difficulty in modeling this since there are basically two binding targets of the antibody – 1.) the antigen via the variable region of the antibody and 2.) The Fc receptor via the constant region of the antibody. A further subtlety is that constant regions of the antibodies can bind to multiple FcR’s, so it’s not like we can say we are measuring IgG1-antigen complex (ISTEST)  binding to the FcR (ISBDAGNT). Modeled this would also mean we’d either blow ISTESTCD terminology or need a work-around such that antibody-antigen complexes could be listed in the SUPPIS.

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The FC receptors, complement proteins, NK and phagocytes are all downstream effectors or cells that are recruited/activated by the FC region of the antibody, whether or not the effector is binding to the FC region is irrelevant. I think only complement 1B binds to the FC region, as well as the various Fc Receptors. The point is that they all are FC-medicated antibody effectors - perhaps this could be our new variable. 

If our end goal is to quantify the antibodies:

If our end goal is to quantify the Fc receptors:

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GR3A158V

Functional IgG antibody