What is the half-life of IgG, and why is this duration significant?

The half-life of IgG is 18-23 days, and this duration is significant for several reasons. Firstly, IgG is the most abundant antibody in the serum and plays a crucial role in the immune response. Its relatively long half-life allows for a sustained immune response, providing prolonged protection against pathogens.

One of the key mechanisms that contributes to the extended half-life of IgG is its ability to bind with the neonatal Fc receptor (FcRn). This receptor is responsible for protecting IgG from degradation within the body, allowing it to remain in circulation longer than other immunoglobulin classes. The interaction with FcRn recycles IgG back into the bloodstream and out of lysosomal degradation pathways, which is vital for maintaining adequate levels of IgG in the immune system over time.

Thus, the binding of IgG to the neonatal Fc receptor not only explains its longer half-life but also illustrates its importance in both maternal immunity transfer to newborns and in sustaining immunity against infections throughout an individual's life.