Nucleolus-associated J chains in myeloma cells: clinical significance

Bone marrow aspirates from 20 patients with multiple myeloma (MM), 4 with smoldering multiple myeloma (S-MM), 1 with idiopathic Bence Jones proteinuria (I-BJP), and 6 with primary macroglobulinemia (PMG) were examined for nucleolus-associated J chain. The incidence of nucleolar J chain-positive (J+) cells among nucleolated cells producing M-component was measured. This incidence (94.0-100%) in terminal MM was significantly higher than that (0-58.0%) in non-terminal MM. Judging from a low incidence in the remission phase, chemotherapy might cause a selective elimination of less differentiated myeloma cells with J+ nucleoli and might have some effect on J chain synthesis. The incidence of nucleolar J+ cells was very low in S-MM. The IgM cells in PMG, where J chain is present in a disulfide-linked form, had no or few J+ nucleoli. No correlation between the incidence of nucleolar J+ cells among nucleolated plasma cells and the percentage of nucleolated cells or that of J+ cells was found. Large J+ nucleoli seemed to be another morphological feature indicating anaplastic myeloma cells. A high incidence of nucleolar J+ cells may be one of the indicators for progressive disease.