Plasma is the fluid of blood that bears blood cells from one place to another. It contains ions, sugars, cholesterol, protein, amino acid, organic acid, enzymes and hormones. It plays a vital role in maintaining the concentration of the constituents and accurately functioning for good health. It contains coagulating agents that help in blood clotting at the site of wounds. After clotting, it releases an amber-like fluid called serum. The serum helps to resolve the clot and prevent infections. It lacks blood clotting agents but has a higher variety of biomarkers. This quality makes both plasma and serum eligible for use in the diagnosis and treatments. In recent clinical diagnostics, plasma and serum are used to detect the concentration of the constituents that confirms severe anomalies like hypoglycemia, diabetes by the concentration of glucose, and occult malignancies like prostate cancer by the concentration of the prostate-specific antigen. In this article, we will study both terms in detail.
Plasma is the suspension of the constituents present in the blood. It is the liquid base of blood that helps in the transportation of stuff like oxygen, carbon dioxide, nutrients, electrolytes and the excretory products of the cell, the derivative of cellular metabolism. The excretory products are transported to the kidney, liver and lung to excrete.
All the blood cells- RBC, WBC and platelets are extracted to obtain a straw-coloured fluid. This fluid is plasma that contains 92-95% of water. Plasma dilutes the constituents, like protein albumin, globulin and fibrinogen, electrolytes including Na+, Cl-, K+, HCO3-, Mg2+ and Ca2+, amino acids, organic acids, vitamins and enzymes etc. Corticosteroids, insulin and thyroxine are released in the blood and regulated vigilantly. Nitrogenous derivatives like creatinine and urea are expelled to the kidney for excretion. The excessive emission of these products results in renal failure. In the liver, coagulating proteins and their inhibitors are produced that include the 6-8% protein of plasma. The fibrinogen is a coagulating protein, converted to fibrin by trapping blood elements that help clot blood at the injury site to reduce blood loss. The antagonists or the inhibitors help to resolve the clot preventing abnormal coagulation. The clot releases a type of liquid called serum. The liver also produces serum albumin that maintains the osmotic pressure of blood vessels and carries important hormones. The α and β globulin transport steroid hormones, lipids, sugar, iron and cholesterol. The γ globulins are the immunoglobulin released by β lymphocytes that develop antibodies against the specific antigens. The bone marrow secretes cytokines which develop blood cells by hematopoiesis. It controls inflammation. The electrolytes and acids control the acid-base balance. They are maintained precisely in a narrow range. The albumin proteins balance the intravascular water amount in endothelial capillaries. The low albumin concentration may cause oedema by water migration from vascular space.
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Serum is a liquid that forms after blood coagulation. This amber-coloured liquid lacks clotting factors or coagulating proteins and blood cells. It contains the factors, electrolytes, and hormones that are uninvolved in blood clotting. The serum is a 90% water suspension of all those constituents. In clinical trials, the serum is used to diagnose the therapeutic index of drug addicts. The supernatants of the centrifugation of the serum sample are used in biopharmaceuticals to diagnose infectious diseases. The antibodies developed against the antigen found in the collected serum are the effective fighter that results in a successful recovery. This is also used to form antiserum, the most considered way of immunotherapy. The serum is also used in protein electrophoresis. A growth factor-rich serum called fetal bovine serum is used in the eukaryotic cell culture. In addition, the cytokine leukaemia inhibitory factor is used to preserve the embryonic stem cell. The serum is used to diagnose disease for its largest range of biomarker variation obscured with efficacy, resolution, sensitivity, reproducibility, multiple degradation mechanisms and the existence of salt and electrolytes. A pre-separated serum albumin protein that is depleted by free flow electrophoresis, enables greater permeation of the proteome by a number of charged analytes.
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| Plasma | Serum |
|---|---|
| Liquid, transparent portion of blood. | Undiluted extracellular liquid of blood. |
| Straw coloured. | Amber coloured. |
| Composed of clotting factor and serum. | Lacks clotting factor. |
| An anticoagulant is used to centrifuge the blood to obtain plasma. | Develops after coagulation of blood. No need for an anticoagulant to centrifuge for obtaining serum. |
| Fibrinogen exists. | No fibrinogen. |
| Contains proteins, immunoglobulins, lipids, electrolytes, glucose and 92-95% of water. | 90% of water in which proteins, minerals, carbon dioxide and hormones are dissolved. |
| 55% of blood. | Less than plasma volume. |
| Concentration= 1.025 g/ml. | Concentration= 1.024 g/ml. |
| Long shelf life, ≤10 years, in -18°C. | Very short shelf life, only for a few months, at 2-6°C. |
| Basic medium of transportation of blood cells and other factors including excretory products from one place to another. | Vital source of electrolysis. |
| Cells are free floating in plasma. | Cells are clotted. |
| Time-consuming, and difficult to separate. | Less time-consuming, easier separation. |
| Transfusion is done on trauma and liver disease patients. | Used in enzyme and hormonal tests. |
| Prevents infection by maintaining the electrolyte balance of the blood. | The presence of electrolysis helps to detect the particular disease in diagnostics. |
Plasma and serum are related to blood. Plasma is the main medium of transport of blood while serum is the liquid that forms after the blood clotting at the site of vascular disruption. Plasma and serum both are lacking blood cells. After extracting the blood cells the liquid obtained by centrifuging with anticoagulants is the plasma. It contains a lot of electrolytes, proteins, lipids, sugar, enzymes and hormones. The serum contains the same things uninvolved in the blood clotting as it lacks blood clotting factors. Both plasma and serum contain 90-95% of water, which dilutes the other factor and balances accurately. Both of these are used to detect diseases for their efficacy and some special features.
Q1. Define plasmapheresis.
Ans. It is a process of extracting the blood cells from blood by centrifugation to separate the plasma and cells, then return the cell to the bloodstream. The plasma is exchanged. It is a second-line autoimmune therapy.
Q2. What is serology?
Ans. The study of serum and other body fluids is called serology.
Q3. State the functions of serum.
Ans.
Q4. What are ELISA and RIA?
Ans. ELISA and RIA both are immunoassays or serological tests detecting antigen-antibody complexes by using enzymes and radioactive isotopes respectively.
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