Chromatographic study of the interrelationships of immunoglobulin A and alpha 1-microglobulin in myelomatosis.

The binding of alpha 1-microglobulin (alpha 1-m) to serum immunoglobulin A (IgA) myeloma proteins have been examined by analytical and preparative Superose high-performance gel chromatography. Enzyme immunoassays showed that in the serum alpha 1-m was bound to monomeric IgA, but not to the polymeric IgA, and was also present in a free form. The IgA-alpha 1-m complexes involved covalent and non-covalent bonds. Considerable variation in the ratio of bound to unbound forms of alpha 1-m was observed that appears to be a result of variation of the IgA alpha heavy chains. Reduction of monomeric IgA produced alpha 1-m-heavy chain complexes, free alpha 1-m, light and alpha heavy chains, and traces of alpha 1-m attached to IgA that was resistant to reduction.