Identification and quantification of half-molecule immunoglobulins
Kawai, T.; Sakurabayashi, I.
Annals of the Academy of Medicine Singapore 9(1): 50-53
1980
ISSN/ISBN: 0304-4602 PMID: 6778364 Document Number: 159673
Abnormal IgA1 half-molecules consisting of one heavy and one light chain were found in a patient (NN) with typical multiple myeloma. Serum total protein was 9.4 g/dl, and the serum protein electrophoresis showed a monoclonal gamma-1 fraction amounting to 43.1%. The patient's serum and urine showed immunoelectrophoretically double arcs against anti-alpha antiserum having the same mobility. No double precipitin ring was demonstrated on single radial immunodiffusion analysis of the serum. The serum and the urine of this patient contained both 7.0S and 3.9S IgA-lambda type myeloma proteins. The IgA half-molecules (3.9S) were found to have a molecular weight of 59,000 daltons and were composed of one alpha-1 chain of about 40,000 daltons and one light chain of 22,000 daltons. Furthermore, enzymatic degradation suggested that the alpha chain of the half-molecules had a large deletion in its Fc portion. We suggest that its heavy and light chains were probably bound noncovalently, since the interchains connecting the heavy and light chains of these IgA half-molecules were easily dissociated with 1% SDS and 8M urea. The similar half-molecules of IgG type were also found in another patient of multiple myeloma.