[A fractionation method for human blood for the separation of subclasses of IgG]

A serum fractionation method which permits a good separation among IgG subclasses is proposed. By loading serum on a Protein A-sepharose column, IgG3 are readily recovered as they do not bind to the Protein A. IgG of the other subclasses are eluted, equilibrated at pH 6 and loaded either on a chromatofocusing column, or on an anion exchanger gel. In these conditions IgG4 are retained, and then recovered by lowering the pH, whereas IgG1 and IgG2 pass through the column and can be recovered separately by absorption on a Protein A column and elution with a decreasing pH gradient.