Systemic immunoglobulin pool (Ig pool)

The systemic immunoglobulin pool refers to the total population of antibodies, primarily Immunoglobulin G (IgG), circulating within the blood and extracellular fluids (Roopenian & Akilesh, 2007). It serves as a cornerstone of the adaptive immune system, providing defense against pathogens through mechanisms such as neutralization, opsonization, and complement activation (Janeway et al., 2001). The homeostasis of the IgG component of this pool is uniquely regulated by the Neonatal Fc receptor (FcRn), which rescues IgG from lysosomal degradation, thereby extending its half-life (Gable et al., 2020). In many autoimmune and alloimmune diseases, this pool contains pathogenic autoantibodies that drive disease progression by attacking self-antigens (Argente-Escrig et al., 2022). Therapeutic strategies targeting this pool aim to either deplete it—most notably through FcRn inhibitors like efgartigimod—or to supplement it in cases of immunodeficiency using intravenous immunoglobulin (IVIG) (Jolles et al., 2005). Monitoring the size and composition of this pool is critical for assessing treatment efficacy and managing the risk of secondary infections.

Other names

Circulating immunoglobulin poolIgG poolPlasma immunoglobulin poolHumoral antibody poolTotal serum immunoglobulins

Neonatal Fc receptor (FcRn) antagonism to increase IgG catabolism; passive immunization via exogenous immunoglobulin administration; mechanical removal via plasmapheresis.