Use of water-soluble polymers for the isolation and purification of human immunoglobulins

By the use of fractional precipitation with high molecular weight nonionic polymers, immune globulins of marked homogeneity were isolated in high yield from either whole serum or commercial samples of immunoglobulins. The isolated fractions were characterized by immunochemical and ultracentrifugal analyses. When the pH was varied from 4.9 to 8.6 and the ionic strength from 0.1 to 2.0, little effect on the precipitation of the immunoglobulins was noted. The immunochemical studies indicated that this fractionation technique is not effective in separating the γ G, γ M, and γ A activities present in the γ-globulins isolated from whole serum or in commercial immunoglobulin preparations. Preliminary experiments indicate that this technique may be used for the isolation of other serum proteins, especially albumin and the α-globulins. In these instances, however, it is important that ionic strength and pH be controlled. The mechanism for the precipitation of serum proteins by PEG has not been established, but it is suggested that the precipitation involves a local dehydration and consequent change in the dielectric constant of the medium immediately surrounding the protein molecules. It would appear that the high-polymer precipitation technique may be an effective and simple method for the isolation of serum proteins with preservation of much of their native properties.