Two-dimensional polyacrylamide gel electrophoresis analysis of cryoglobulins and identification of an IgM-associated peptide

J Immunol Methods. 1994 Jul 12;173(1):63-75. doi: 10.1016/0022-1759(94)90284-4.


The clonality of immunoglobulins (Igs) in cryoprecipitates (n = 41) was studied by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). Our series included 24 cryoglobulins characterized by immunofixation electrophoresis (IF), 12 'trace amount' cryoglobulins, defined by a protein content in the precipitate of less than 0.05 mg/ml of serum, and five cryoglobulins of undetermined protein composition by IF. 2-D PAGE analysis showed polyclonal IgG associated either with monoclonal Igs (type II cryoglobulins; n = 14) or with polyclonal IgM (type III cryoglobulins; n = 14). In ten cryoprecipitates (two 'trace amount' cryoglobulins as well as seven of 19 type II and as one of five type III cryoglobulins by IF) polyclonal IgG were associated with a mixture of polyclonal and monoclonal IgM. These cryoglobulins were tentatively named type II-III cryoglobulins. A monoclonal IgM was observed in one cryoprecipitate (type I cryoglobulins). Two cryoglobulins presented unexpected 2-D patterns, characterized by the presence of oligoclonal IgM, with trace amounts of Igs of different isotypes (tentatively named type II-III(variant) cryoglobulins). A peptide of 44 kDa with a pI of 5.45 was observed in all cryoglobulins containing IgM (n = 40). This peptide was also present in purified monoclonal or polyclonal IgM fractions. N-terminal microsequencing (12 amino acid residues) revealed that this IgM-associated peptide was an unknown protein. Our results highlight the role of 2-D PAGE as an aid in the analysis of cryoglobulins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Antibodies, Monoclonal / blood
  • Cryoglobulinemia / blood
  • Cryoglobulinemia / immunology
  • Cryoglobulins / analysis*
  • Cryoglobulins / classification
  • Electrophoresis, Gel, Two-Dimensional / methods*
  • Humans
  • Immunoglobulin Isotypes / blood
  • Immunoglobulin M / blood*
  • Isoelectric Point
  • Molecular Sequence Data
  • Molecular Weight
  • Peptides / blood*
  • Peptides / chemistry
  • Peptides / genetics


  • Antibodies, Monoclonal
  • Cryoglobulins
  • Immunoglobulin Isotypes
  • Immunoglobulin M
  • Peptides