IgD was first identified in 1965, and like other immunoglobulins, exists as both secreted and membrane forms. Its level in plasma is low with a mean concentration of 30 ug/ml. IgD is present in large quantities on the surface membrane of a majority of human circulating B lymphocytes. IgD enhances humoral immune responses through its induction of IgD-receptor expression on T lymphocytes. Ref.: Coico RF, Siskind GW, Thorbecke GJ 1988. Immunol. Rev. 105:45. Prepared from plasma shown to be non reactive for HbsAG, anti-HCV, anti-HBc, and negative for anti-HIV 1 & 2 by FDA approved tests. >95percent pure by SDS-PAGE.