Abstract: A method for purifying human or other alpha-l proteinase inhibitor (&agr;1-PI) from a solution (which may be derived from the milk of a transgenic animal expressing the &agr;1-PI) which comprises contacting the solution with a cation exchange substrate under conditions sufficient to bind non-tg-&agr;1-PI contaminants to the substrate while not substantially binding tg &agr;1-PI to the substrate. Using the preferred embodiment, the purified tg &agr;1-PI contains as little as 40 pg non-&agr;1-PI-whey protein per mg total protein.

Abstract: A method for purifying human or other alpha-1 proteinase inhibitor (&agr;1-PI) from a solution (which may be derived from the milk of a transgenic animal expressing the &agr;1-PI) which comprises contacting the solution with a cation exchange substrate under conditions sufficient to bind non-tg-&agr;1-PI contaminants to the substrate while not substantially binding tg &agr;1-PI to the substrate. Using the preferred embodiment, the purified tg &agr;1-PI contains as little as 40 pg non-&agr;1-PI-whey protein per mg total protein.

Abstract: A method of controlling the amount of a biologically active substance binding to a cell surface having both receptors to the substance and receptors for the Fc domain of an antibody that can complex with the substance or other antibodies that can complex with the substance. By exploiting the generally more numerous Fc receptor sites, substance binding can be increased and/or controlled. Method contemplates controlling amounts of substances such as cytokines, hormones, and growth factors that are associated with cells such as monocytes, macrophages, granulocytes, B cells, T cells, and platelets. Method is illustrated using conjugated antibodies to tissue necrosis factor (TNF) to increase the binding of TNF to monocytes.

Abstract: Method of purifying a protein from a solution of substances comprising the steps of passing the solution through an ion exchange material at a pH which facilitates binding of the protein of interest, washing the bound protein at a different pH at which the bound protein does not elute but which the free protein would not bind to the ion exchange material, and then eluting the protein at a pH which facilitates elution. Method is especially useful in purification of antibodies such as antibodies to tumor necrosis factor.