Two-dimensional gel electrophoresis of serum specimens from patients with monoclonal gammopathies.

We modified the ISO-DALT two-dimensional gel electrophoresis system to allow the routine examination of serum specimens from patients with monoclonal gammopathies. This system, MC-Iso 1, is characterized by a broad pH gradient for resolving the basic immunoglobulin heavy and light chains. The increased resolution of basic proteins may be explained on theoretical grounds by an increase in voltage in this region of the cell. Ancillary techniques, such as those for albumin removal and pI assignment through use of charge standards, have also been implemented. The locations of immunoglobulin heavy chains have been confirmed by examination of over 250 serum samples as well as by "electro-blotting," with use of specific antisera. IgG subclass may also be predicted by location, but not with perfect accuracy. Differentiation of kappa and lambda light chains by relative mobility has been examined; the predictive value for correct identification of kappa chains is 83%, that for lambda chains 69%. Several unknown proteins have been observed in macroglobulinemia, related to mu heavy chain. Finally, we have determined that there is excellent correlation between non-denaturing isoelectric focusing and our system for pI assignment of light chains. This has importance due to reports of the potential importance of light-chain pI in the development of renal disease in patients with monoclonal gammopathies.