Autoantibody activity of the immunoglobulin secreted by a follicular B-cell lymphoma

In patients with B-cell lymphoma, only in rare cases a secreted paraprotein is found, and in very few of them an associated autoantibody activity has been demonstrated. Here we report the case of a patient with a low-grade B- cell lymphoma with a serum biclonal paraprotein (G,M)lambda and severe eryt hroblastopenia. Indirect immunofluorescence studies of total serum revealed cytoplasmic (Hep-2 cells) and extracellular matrix (rat tissue sections) s taining, suggestive of a new specificity. After gel filtration of serum sam ples, only the IgM-containing fraction showed the same pattern of staining. Tumor-derived hybridomas expressed an unmutated V3-11 gene identical to th at found in tumor samples and secreted an IgM immunoglobulin endowed with t he same reactivity, which confirms the tumoral origin of the tissue-reactiv e protein. The results suggest a link between the autoimmune condition in t his patient and the novel specificity displayed by the tumor-derived immuno globulin.