Source:http://linkedlifedata.com/resource/umls/id/C1518416
NCI: The serum of a healthy, unvaccinated adult horse. Sera are lipid-extracted, dialyzed, sterilized, and filtered and may contain preservatives such as sodium azide. Normal horse serum may be used as a blocking agent to reduce background from non-specific binding or as a negative control in immunoassays. (NCI04)