IgGpassaget

IgGpassaget is a term used in immunology to describe the passage or translocation of immunoglobulin G (IgG) across biological barriers. The concept covers IgG movement from mother to fetus during pregnancy, as well as cellular transcytosis across epithelial and endothelial barriers and the systemic recycling that preserves circulating IgG. In some literature, the term is used as a generic label for IgG transport processes rather than a distinct pathway.

Mechanism: The process is largely mediated by the neonatal Fc receptor (FcRn). FcRn binds IgG in acidic endosomal compartments and, after transcytosis, releases it at neutral pH on the opposite side. This mechanism explains placental transfer of maternal IgG to the fetus and the absorption of IgG from the intestinal lumen in newborns. In adults, FcRn also rescues IgG from lysosomal degradation, extending its half-life.

Clinical and research relevance: Subclass differences influence transfer efficiency; IgG1 and IgG3 are commonly transferred more efficiently than others. Abnormalities in IgGpassaget can affect neonatal immunity, susceptibility to infections, or response to vaccines. Therapeutic antibodies leverage FcRn pathways to achieve longer systemic exposure, and Fc-engineering aims to optimize this interaction.

Notes: IgGpassaget is not a formal diagnostic category but a descriptive term used in discussions of antibody pharmacokinetics and maternal-fetal immunology. Researchers may refer to IgG transcytosis or FcRn-mediated transport as more precise terms.