Elicited antibody nature of human monoclonal protein with anti-streptolysin O activity--analysis with monoclonal anti-idiotype antibody.

Sera from 7 patients with multiple myeloma having antistreptolysin O (ASO) activity in high titers were detected by a streptolysin O (SLO) inhibition assay. However, activity was in low titer when assayed by a passive agglutination assay. The discrepancy between these 2 assays raised some doubts as to whether these monoclonal proteins (M.protein) bond to SLO in the same manner as elicited antibodies. Immunochemical analysis and idiotope analysis using monoclonal antibody to one of these M.proteins strongly suggest that M.protein with ASO activity bind to SLO in a manner similar to elicited antibody. The discrepancy between the 2 assays might be due to differences in the antigenic structure of different forms of the SLO molecule.