Serum (blood) toxic response. 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
Clotting time Clotting time Clotting time is the time required for a sample of blood to coagulate in vitro under standard conditions. There are various methods for determining the clotting time, the most common being the capillary tube method. It is affected by calcium ion levels and many diseases. Normal value of clotting time is 8 to 15 minutes. For the measurement of clotting time by test tube method, blood is placed in a glass test tube and kept at 37° C. The required time is measured for the blood to clot. There are several other methods, including testing for those on