Differentiation of follicular lymphoma cells after autologous bone marrow transplantation and haematopoietic growth factor treatment

A patient with follicular lymphoma developed a striking but transient plasmacytosis in blood and bone marrow with paraproteinaemia after treatment by autologous bone marrow transplantation and interleukin-3 (IL-3). By immunophenotyping, cytogenetics and Southern blotting, we proved that the plasma cells were clonally related to the original lymphoma cells. This event was preceded by fever accompanied by high IL-6 concentrations. The patient recovered spontaneously and had a long-lasting remission. We speculate that the bone marrow-derived malignant B cells were stimulated by IL-3 and IL-6 into terminally differentiated plasma cells.