Serum albumin and other plasma opsonins

Serum albumin is the most abundant protein in human plasma, serving as the primary regulator of colloidal osmotic pressure and a versatile carrier for hormones, fatty acids, and numerous drugs (UniProt P02768). Plasma opsonins, including immunoglobulins and complement proteins like C3b, are critical components of the immune system that tag foreign pathogens for destruction by phagocytes (NCBI, 2022). This collective group of proteins is essential for maintaining systemic homeostasis and mediating the body's defense against infection. In clinical practice, albumin is used as a therapeutic volume expander in conditions like cirrhosis or nephrotic syndrome, while opsonins are targeted or supplemented via intravenous immunoglobulin (IVIG) therapies (DrugBank DB00020). Because albumin binds many drugs, changes in its concentration can significantly impact the pharmacokinetics and toxicity of highly protein-bound medications. Furthermore, deficiencies in opsonins can lead to severe, recurrent bacterial infections, highlighting their role in protective immunity (StatPearls, 2023).

Other names

Plasma proteinsBlood opsoninsSerum proteinsHuman serum albuminComplement components

Serum albumin functions as a high-capacity carrier protein that reversibly binds and transports various ligands, while opsonins facilitate phagocytosis by coating pathogens and binding to specific receptors on immune cells (StatPearls, 2023; NCBI, 2022).