[A simple method of isolating monoclonal immunoglobulin M, possessing rheumatoid activity]

A simple procedure for obtaining highly purified preparations of native monoclonal (Waldenström's disease) immunoglobulin M possessing a rheumatoid activity (IgM-RF) has been developed. The method is based on the use of affinity chromatography with a new readily available adsorbent (immunoglobulin G-porous glass) and 3 M LiCl in Tris-buffer pH 8.3-8.4 able to induce the dissociation of the IgM-RF-IgG complex. The IgM-RF preparation thus obtained was characterized in terms of amino acid composition (relative to conventional monoclonal IgM), carbohydrate composition and structure of oligosaccharide moieties of a complex type. It was shown that some dissociation conditions for the IgM-RF-IgG complex routinely used to isolate IgM-RF provoke irreversible denaturation of IgM-RF when applied to a preliminarily purified complex.