Using mass spectrometry to monitor monoclonal immunoglobulins in patients with a monoclonal gammopathy

David R. Barnidge, Surendra Dasari, Chad M. Botz, Danelle H. Murray, Melissa R. Snyder, Jerry A. Katzmann, Angela Dispenzieri, David L. Murray

Research output: Contribution to journalArticle

54 Scopus citations

Abstract

A monoclonal gammopathy is defined by the detection a monoclonal immunoglobulin (M-protein). In clinical practice, the M-protein is detected by protein gel electrophoresis (PEL) and immunofixation electrophoresis (IFE). We theorized that molecular mass could be used instead of electrophoretic patterns to identify and quantify the M-protein because each light and heavy chain has a unique amino acid sequence and thus a unique molecular mass whose increased concentration could be distinguished from the normal polyclonal background. In addition, we surmised that top-down MS could be used to isotype the M-protein because each immunoglobulin has a constant region with an amino acid sequence unique to each isotype. Our method first enriches serum for immunoglobulins followed by reduction using DTT to separate light chains from heavy chains and then by microflow LC-ESI-Q-TOF MS. The multiply charged light and heavy chain ions are converted to their molecular masses, and reconstructed peak area calculations for light chains are used for quantification. Using this method, we demonstrate how the light chain portion of an M-protein can be monitored by molecular mass, and we also show that in sequential samples from a patient with multiple myeloma the light chain portion of the M-protein was detected in all samples, even those negative by PEL, IFE, and quantitative FLC. We also present top-down MS isotyping of M-protein light chains using a unique isotype-specific fragmentation pattern allowing for quantification and isotype identification in the same run. Our results show that microLC-ESI-Q-TOF MS provides superior sensitivity and specificity compared to conventional methods and shows promise as a viable method of detecting and isotyping an M-protein.

Original languageEnglish (US)
Pages (from-to)1419-1427
Number of pages9
JournalJournal of Proteome Research
Volume13
Issue number3
DOIs
StatePublished - Mar 7 2014

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Keywords

  • Monoclonal gammopathy
  • immunoglobulin
  • isotype
  • mass spectrometry
  • multiple myeloma
  • top-down MS

ASJC Scopus subject areas

  • Biochemistry
  • Chemistry(all)

Cite this

Barnidge, D. R., Dasari, S., Botz, C. M., Murray, D. H., Snyder, M. R., Katzmann, J. A., Dispenzieri, A., & Murray, D. L. (2014). Using mass spectrometry to monitor monoclonal immunoglobulins in patients with a monoclonal gammopathy. Journal of Proteome Research, 13(3), 1419-1427. https://doi.org/10.1021/pr400985k