Fcgrt, also known as the gene encoding the neonatal Fc receptor (FcRn) α-chain, is crucial for the trafficking of endogenous and exogenous IgG molecules and albumin in various tissues [6]. FcRn binds to IgG, protecting it from lysosomal degradation by transporting it back to the cell surface for re-entry into the circulation, thus extending the serum IgG lifespan. This process is involved in the function of IVIg and is relevant to the pharmacokinetics of therapeutic monoclonal antibodies [1,8]. Animal models like rhesus macaques, which have VNTR polymorphisms in Fcgrt affecting IgG levels, can be potential models for studying the immunological response related to Fcgrt [2,7].

In humans, Fcgrt polymorphisms, such as the VNTR3/2 in myasthenia gravis patients, may affect the duration of infused IgG in the circulation and IVIg effectiveness [1]. Also, in enterovirus B infection, FcRn binds to the virus particles through its FCGRT subunit, acting as the uncoating receptor, which provides a structural basis for understanding enterovirus entry mechanisms [3]. DNA methylation in regulatory regions of Fcgrt contributes to FcRn expression, and microRNA-3181 is an epigenetic regulator of Fcgrt expression [4,6]. In Indian water buffaloes, Fcgrt polymorphisms are associated with colostral IgG concentration, which is important for neonatal passive immunity [5].

In conclusion, Fcgrt plays a vital role in IgG and albumin trafficking, influencing the effectiveness of immunotherapies, the course of certain infections, and neonatal immunity. Studies on Fcgrt using genetic models help in understanding its function in various biological processes and disease conditions, providing insights for the development of more effective treatments related to IgG-based therapies and infectious diseases [1-9].