A substance used to separate antigens from a mixture, usually as a part of immunoaffinity chromatography. The immunoadsorbent is a solid matrix to which antibodies are bound; as the mixture flows through the column and past the stationary immunoadsorbent within, the antigens become attached to the antibodies and stay within the column while the rest of the mixture continues through to the end.

From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.