COMMON CLONAL ORIGIN OF LYMPHOCYTES AND PLASMA-CELLS IN SPLENIC LYMPHOMA WITH VILLOUS LYMPHOCYTES

In two-thirds of patients with splenic lymphoma with villous lymphocyt es (SLVL) a small amount of M-protein can be detected in association w ith the presence of plasma cells in the peripheral blood (PB) and/or b one marrow (BM). However, it is not known whether lymphoma cells and p lasma cells originate from the same clone. In this report we describe a case of SLVL which was characterized by the presence of marked monoc lonal gammopathy (IgG-kappa 90 g/l) and increased plasma cells in the BM. In an attempt to elucidate the origin of lymphoma cells and plasma cells, we performed morphological, cytogenetic and molecular studies on PB mononuclear cells (PBMNC) without plasma cells and BMMNC contain ing 10% plasma cells from this patient. Immunofluorescence showed that lymphoma cells and plasma cells were positive for cytoplasmic gamma h eavy and kappa light chains. Well-developed endoplasmic reticulum was observed in the cytoplasmic organelles of PBMNC using an electron micr oscope, The mean IgG concentration in the 3 d supernatant cultures of PBMNC was 374 +/- 24 mu g/l. More than 50% PBMNC differentiated into p lasmacytoid cells in 6 d of liquid culture with IL-3 and IL-6, Analysi s by two-colour FISH revealed that karyotypic abnormalities of monosom y X and trisomy 17 existed simultaneously in both lymphoma cells and p lasma cells. JH gene rearranged bands from PBMNC and BMMNC by Southern blot hybridization were identical, whereas DNAs from PBMNC failed to hybridize with the C mu probe. These observations strongly suggest tha t lymphoma cells and plasma cells originate from the same clone, and t hat plasma cells, as well as lymphoma cells, which have undergone clas s switch recombination, could produce IgG type M-protein in this case.