Characterization of a homogeneous paraprotein from a horse with spontaneous multiple myeloma syndrome.

A novel myeloma paraprotein has been isolated from a horse with a lymphoid tumor. The protein was a euglobulin and consequently was readily isolated from serum in pure form and high yield by simple dilution in distilled water. The purified intact protein had a molecular weight of 150,000 and was composed of heavy and light chains, both of which had blocked amino-termini and were thus not susceptible to amino-terminal sequence analysis. The amino acid compositions of these respective chains corresponded to those of comparable chains from immunoglobulins of other species. Peptide maps of paraprotein light chains prepared by high pressure liquid chromatography corresponded in part to those of normal pooled equine light chains. The identification of this paraprotein as an equine AI (aggregating immunoglobulin) protein was confirmed by serological analysis using a specific antiserum. The relationship of this particular protein to other members of the immunoglobulin family was further demonstrated by the production of an anti-idiotypic antiserum individually specific for this molecule.