Antibody immunoglobulin G (IgG) has numerous functions in human immune defense system, and it is increasingly used as antigen-binder or a critical link between adaptive and innate immunity in the non-clinical or clinical research. Since 2013, 31 new monoclonal antibodies (mAbs) and ten biosimilars have been introduced, creating a global market of a total of 57 mAbs and 11 biosimilars in clinical use by the end of 2017, based on public information provided by the FDA in the USA and the European Medicines Agency (EMA) in the EU. Furthermore, in 2014 the FDA approved the first bispecific Fab (blinatumumab, trade name Blincyto®), which represents a new class of drugs, the bispecific T cell engagers (BiTEs®), that can form a link between cytotoxic T cells and pathogenic targets. In addition, in 2017 the first full-length bispecific mAb engineered on the structure of a humanized IgG4 (emicizumab, trade name Hemlibra®) was approved. Thus, although antibodies of Fab or IgG4 other than IgG1 have recently been approved by the FDA, most therapeutic antibodies have been still developed based on IgG1 templates. IgG1 has two functional domains; 1) Fab domain which recognizes pathogenic target and 2) Fc domain which triggers numerous cellular phenotypes via Fc-binding proteins, which are six FcγRs, complement C1q, FcRL5, FcRn, TRIM21, DC-SIGN, and type II lectin receptors.