This product is made from sera collected from healthy adult horses. Serum pooled from several animals is heat-treated, centrifuged to remove precipitates and filtered. The sera are tested with the appropriate antibody to check for possible cross-reactivities and supplied undiluted with 0.08% sodium azide as a preservative. When diluted, this reagent can be used for blocking non-specific binding when horse secondary antibodies are used in immunohistochemistry (IHC) assays. It can also be used as an antibody diluent.