Human serum is obtained from blood plasma after fibrinogen and other clotting factors have been removed. Primary research applications include immunohistochemical staining and human leukocyte antigen (HLA) typing, as well as an addition to cell culture media. Human sera provide a more comparable cell culture environment than animal sera when culturing human cells, a fact that particularly comes into play when working with immune cells such as lymphocytes and macrophages.
Human serum is available from individual or pooled donors and can be differentiated by age, sex, and a variety of disease states, depending on your research focus. Off-the-clot serum is from blood that has been allowed to clot spontaneously after centrifugation, with no anticoagulant added. Type AB serum is often used when minimized immunoactivity is desired, since it does not contain interfering anti-A or anti-B antibodies.