Monoclonal IgG3-kappa and IgG1-lambda proteins with different idiotypic determinants present in a single patient.

Two monoclonal proteins belonging to IgG3-kappa and IgG1-lambda subclasses were detected in a single patient. Immunochemical analysis revealed that the idiotypic determinants of the two proteins were different. Examination of bone marrow by an immunofluorescence technique indicated that these two proteins were produced in different cells, although both kappa and lambda chains were present in a minute proportion of the cells. J chain was present in all cells that produced IgG.