METHOD FOR THE ISOLATION OF BIOLOGICALLY-ACTIVE MONOMERIC IMMUNOGLOBULIN-A FROM A PLASMA FRACTION

A purification method for immunoglobulin A (IgA) yielding monomeric Ig A with a purity of over 97% has been developed. This procedure uses et hanol-precipitated plasma (Cohn fraction III precipitate) as the start ing material and includes heparin-Sepharose adsorption, dextran sulfat e and ammonium sulfate precipitation, hydroxyapatite chromatography, b atch adsorption by an anion-exchange matrix and gel permeation. Additi onal protein G Sepharose treatment leads to an IgA preparation of grea ter than 99% purity. The isolated IgA presented with an IgA subclass d istribution, equivalent to IgA in unfractionated plasma, and was biolo gically active, as was shown by its ability to down-modulate Haemophil us influenzae-b-induced IL-6 secretion of human monocytes.