In blood, the serum ( or ) is the component that is neither a blood cell (serum does not contain white or red blood cells) nor a clotting factor; it is the blood plasma not including the fibrinogens. Serum includes all proteins not used in blood clotting (coagulation) and all the electrolytes, antibodies, antigens, hormones, and any exogenous substances (e.g., drugs and microorganisms). The study of serum is serology, which may also include proteomics. Serum is used in numerous diagnostic tests, as well as blood typing. Blood is centrifuged to remove cellular components. Anti-coagulated blood yields plasma containing fibrinogen and clotting factors. Coagulated blood (clotted blood) yields serum without fibrinogen, although some clotting factors remain. Serum is an essential factor for the self-renewal of embryonic stem cells in combination with the cytokine leukemia inhibitory factor. The serum of convalescent patients successfully recovering (or already recovered) from an infectious disease can be used as a biopharmaceutical in the treatment of other people with that disease, because the antibodies generated by the successful recovery are potent fighters of the pathogen. Such convalescent serum ( antiserum) is a form of immunotherapy.
Purification strategiesBlood serum and plasma are one the largest source of biomarkers, whether for diagnostics or therapeutics. Its vast dynamic range, further complicated by the presence of lipids, salts, and post-translational modifications, as well multiple mechanisms of degradation, presents challenges in analytical reproducibility, sensitivity, resolution, and potential efficacy. For analysis of biomarkers in blood serum samples, it is possible to do a pre-separation by free-flow electrophoresis that usually consists of a depletion of serum albumin protein.Nissum M., Foucher AL.: Analysis of human plasma proteins: a focus on sample collection and separation using free-flow electrophoresis. In: Expert Rev Proteomics. Nr. 5, 2008, S. 571–87. This method enables greater penetration of the proteome via separation of a wide variety of charged or chargeable analytes, ranging from small molecules to cells.
Usage noteLike many other mass nouns, the word serum can be pluralized when used in certain senses. To speak of multiple serum specimens from multiple people (each with a unique population of antibodies), physicians sometimes speak of sera (an irregular plural, as opposed to *serums).
- Human serum albumin
- Serum iron
- Serum protein electrophoresis
- Serum total protein