Serum (/ˈsɪərəm/) is the fluid and solvent component ofblood which does not play a role inclotting.[1] It may be defined asblood plasma without theclotting factors, or as blood with all cells and clotting factors removed. Serum contains allproteins except clotting factors (involved inblood clotting), including allelectrolytes,antibodies,antigens,hormones; and anyexogenous substances (e.g.,drugs,microorganisms). Serum also does not contain all the formed elements of blood, which include blood cells, white blood cells (leukocytes,lymphocytes), red blood cells (erythrocytes), andplatelets.[citation needed]
The study of serum isserology. Serum is used in numerousdiagnostic tests as well asblood typing. Measuring the concentration of various molecules can be useful for many applications, such as determining thetherapeutic index of adrug candidate in aclinical trial.[2]
To obtain serum, ablood sample is allowed to clot (coagulation). The sample is thencentrifuged to remove the clot and blood cells, and the resulting liquidsupernatant is serum.[3]
The serum ofconvalescent patients successfully recovering (or already recovered) from aninfectious disease can be used as abiopharmaceutical in the treatment of other people with that disease, because theantibodies generated by the successful recovery are potent fighters of thepathogen. Suchconvalescent serum (antiserum) is a form ofimmunotherapy.[citation needed]
Serum is also used inprotein electrophoresis, due to the lack offibrinogen which can cause false results.[citation needed]
Fetal bovine serum (FBS) is rich ingrowth factors and is frequently added togrowth media used for eukaryoticcell culture. A combination of FBS and the cytokineleukemia inhibitory factor was originally used to maintainembryonic stem cells,[4] but concerns about batch-to-batch variations in FBS have led to the development of serum substitutes.[5]
Vertebrate sera (such as FBS) or invertebrate hemolymph were also used for the growth of insect cell lines as a source of nutrients and growth factors. Cost and other factors lead to the development of replacement media and cell lines that grow well in these media.[6]
Blood serum and plasma are some of the largest sources ofbiomarkers, whether for diagnostics or therapeutics. Its vast dynamic range, further complicated by the presence of lipids, salts, and post-translational modifications, as well as 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 byfree-flow electrophoresis that usually consists of a depletion of serumalbumin protein.[7] 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.[citation needed]
Like many othermass nouns, the wordserum can be pluralized when used in certainsenses. To speak of multiple serum specimens from multiple people (each with a unique population of antibodies), physicians sometimes speak ofsera (the Latin plural, as opposed toserums).[citation needed] Etymologically serum is derived from the Proto-Indo-European *ser- ("to flow, run").
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