A special receptor (FcRn) saves antibodies from being destroyed inside cells and helps shuttle them — along with any germs they’re attached to — to the right place to be shown to immune cells.
Scientific Claim
FcRn binds IgG in acidic endosomes and recycles it to the cell surface, preventing degradation and extending IgG half-life, while also facilitating antigen presentation by directing IgG immune complexes to MHC class II compartments.
Original Statement
“FcRn is predominantly detected in the endosomal compartment and constitutively cycles between there and the plasma membrane. At the low pH of these intracellular compartments, it binds to IgG with high affinity (62, 68, 69). Internalized monomeric IgG binding to FcRn in these acidic endosomal compartments and can be recycled to the cell surface where the IgG is released upon neutral pH change, thereby avoiding lysosomal destruction inside the cell and extending the half-life of IgG molecules in the circulation (70, 71). ... FcRn is ideally situated to engage IgG-ICs within endolysosomal compartments and to regulate IgG-IC trafficking and subsequently MHC class II-mediated antigen presentation (73–78).”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
definitive
Can make definitive causal claims
Assessment Explanation
The described mechanism is well-established through biochemical, cellular, and genetic experiments cited in the review. Definitive language is appropriate for this conserved biological process.
Evidence from Studies
Supporting (1)
This study shows that when antibodies (IgG) grab onto germs, special cell receptors help bring them inside the cell and send them to the right place to teach immune cells what to attack—supporting the idea that IgG helps present threats to the immune system.