Overview
Serum is the clear, yellowish fluid that remains after blood has clotted and the cells and clotting factors have been removed. In a broader sense the term is applied to comparable cell-free fluids derived from tissues or biological sources. Because it contains soluble proteins, hormones and antibodies but lacks fibrinogen and most clotting proteins, serum is a key material in medicine, research and commerce.
Composition and preparation
Blood serum contains water, electrolytes, small molecules, albumin, globulins and other soluble proteins. Routine preparation involves allowing collected blood to clot, then separating the liquid by centrifugation or decanting. Laboratory protocols may include heat treatment or filtration to inactivate complement proteins and reduce microbial risk; handling follows biosafety guidance because serum can carry infectious agents.
Medical, diagnostic and therapeutic uses
Serum is central to serology, the laboratory testing of antibodies and antigens for infection, immunity and autoimmune conditions. Antiserum—serum enriched with antibodies produced by immunizing an animal or donor—has been used for passive immunization and as antitoxins. Convalescent serum from recovered patients can supply antibodies for transient protection and was explored in several infectious disease outbreaks.
Laboratory and commercial uses
In cell biology, fetal bovine serum and other serum supplements provide growth factors and nutrients for in vitro culture of cells. Serum fractionation yields components such as immunoglobulins and albumin for research and therapeutic products. In cosmetics, the term "serum" denotes lightweight, concentrated topical formulations designed to deliver active ingredients efficiently to the skin.
Distinctions and notable facts
- Plasma vs serum: plasma is obtained from anticoagulated blood and retains clotting proteins; serum results from coagulated blood and lacks fibrinogen.
- Antiserum and hyperimmune preparations: concentrated antibody products differ from ordinary serum and are standardized for medical use.
- Safety: because serum may contain pathogens, it must be screened, handled with precautions and, for human therapeutic use, processed to meet regulatory standards.
Across clinical diagnostics, therapeutics, research and consumer goods, serum remains a versatile and widely used biological material whose properties and handling vary according to purpose and regulatory context.