There are two types of plasma donations, recovered plasma and source plasma -- the plasma's the same, it's just the method of donation that differs.
To understand plasma donations, first we need to know a little bit about blood. Whole blood donations -- those blood drive donations where blood is drawn through a needle into a plastic blood bag -- include all the components of our blood. A little less than half (45 percent) of human blood is made up of cells -- red cells, white cells and platelets (small cell fragments, and unlike the red and white cell types these are colorless) -- and the other half (about 55 percent blood volume) is plasma, the pale yellow fluid those cells are suspended in.
When you donate whole blood, and most donations are whole blood, the individual components of that blood can be separated and used independently when and where they're needed; plasma donated through this method is called recovered plasma. It's possible that a single donation of whole blood could go on to help as many as three people, and it's estimated that just one whole blood donation contains nearly 250 milliliters of recovered plasma [source: American Red Cross, Baxter].
It's also possible to donate components of your blood, instead of just the complete package. During red blood cell donation, for example, called double red cell donation, the platelets and plasma are separated from the blood cells and transfused back into the donor during donation; platelets, as well, can be donated, through a similar cell-separation process. And plasma, too, can be donated as a blood component.
The process of donating plasma is called plasmapheresis, and plasma donation begins a lot like any other blood donation, with a needle in the arm. The blood flows from the donor's arm through an IV line and into an apheresis machine where centrifuge is used to separate the blood components. Your blood cells and platelets are then transfused back into your body with a little saline to make up the lost blood volume of the donated plasma.
Plasma is mostly water, but the 8 percent that isn't is made up of proteins and mineral salts (you'll also find hormones, fats, sugars and vitamins in there). Blood proteins include albumin, a globular protein made by the liver; gamma globulins, which are proteins that contain antibodies against bacterial and viral infections, and blood-clotting proteins such as fibrinogen. During plasmapheresis these proteins are removed and collected, and then used to manufacture therapeutic products used to prevent, manage and treat certain rare diseases, life-threatening diseases, chronic illness and genetic conditions. As many as 500 unique proteins have been identified in human blood, and as many as 150 of them are used in therapeutic products [source: DonatingPlasma].
Plasma donated through plasmapheresis is called source plasma, and it's estimated that a single person can supply between 600 and 800 milliliters of plasma in one donation [source: Baxter]. Source plasma donors who donate through plasma donation centers may be compensated for their time, although compensation rates and rules may vary; and any plasma that's purchased rather than donated must be used in manufacturing rather than in human transfusions.