Plasma proteins are proteins found in the blood plasma, the clear, protein-rich fluid which is left behind when platelets, red blood cells, and white blood cells are removed from the blood. These proteins play a number of important roles in the human body, and levels of plasma proteins are sometimes evaluated in a laboratory analysis to gather information about a patient's general health and specific health issues which a patient may be experiencing. These proteins make up around 7% of the total blood volume, with levels which can fluctuate at times.
Some common plasma proteins include albumin, which is by far the most common, along with fibrinogen and globulin, which is broken into globulin alpha, globulin beta, and globulin gamma. Trace amounts of other proteins can also be found in the blood plasma, usually in concentrations of less than one percent of the total plasma, which can make them difficult to identify, especially with only basic blood screening tools available.
Plasma helps to regulate the body's osmotic pressure, which keeps the body's systems working properly. It also transports various compounds needed by the body, in addition to playing a role in immune system function and blood clotting. An imbalance of plasma proteins can lead a patient to experience symptoms ranging from abnormally dilated blood vessels to a weakened immune system.
Fibrinogen is primarily involved in blood clotting, while albumin acts as a transporter and a regulator of osmotic pressure. The globulins are involved in transport and immune processes. With the exception of globulin gamma, the plasma proteins are synthesized in the liver. Imbalances in the plasma count can indicate that the liver is experiencing problems which interfere with its normal function, and an assessment of these proteins may be utilized in a workup which is designed to shed light on a patient's liver health.
In addition to being important to bodily function, plasma proteins are also valuable medical products. A number of pharmaceuticals can be manufactured from plasma proteins, with the proteins being extracted from donor plasma or synthesized in the laboratory. Like other blood products, plasma proteins have to be handled carefully, because they can be a source of infectious disease if they are not properly screened for safety before transfusion. Donors are also usually screened before their plasma or blood donations are taken, with the goal of removing risky donors from the pool of plasma and blood sources.