Immunoglobulin G (IgG) and neonatal Fc-receptor (FcRn) dynamics in IgG multiple myeloma∗

The neonatal Fc receptor (FcRn) binds immunoglobulin G (IgG) and diverts it away from the degradative pathway, resulting in a high plasma concentration of IgG in healthy adults. At elevated IgG concentrations FcRn receptors become increasingly saturated and a greater proportion of IgG molecules is degraded. The half-life of IgG is therefore related with its plasma concentration. In IgG multiple myeloma malignant plasma cells produce large quantities of IgG which can be used as a tumour marker. Following therapy, a proportion of the malignant plasma cells are killed and the production of IgG correspondingly decreases. However, the variable half-life due to FcRn recycling effects should also be taken into account if serum IgG is to be used as an accurate measure of treatment success. In this work we present initial investigations into the dynamics of IgG in multiple myeloma using lumped-parameter models.