IL-1β expression in IgM monoclonal gammopathy and its relationship to multiple myeloma

We have shown that IL-1β is not detectable in normal plasma cells but is produced by plasma cells from virtually all patients with multiple myeloma (MM). To extend our earlier work, IL-1β expression was determined in 13 newly diagnosed patients with IgM monoclonal gammopathy. Eleven patients with Waldenstrom's macroglobulinemia (WM) and two patients with IgM MM were investigated for IL-1β expression by in situ hybridization (ISH). All patients with WM had bone marrow biopsies consistent with the diagnosis, an IgM M-protein in the serum, and subsequently required chemotherapy. Seven of 11 patients with WM had an M-protein >3 g/dl and five patients had bone surveys performed that were negative for osteolytic disease. Two patients were diagnosed with IgM MM because of the presence of significant osteolytic disease on a metastatic bone survey. ISH for kappa, lambda, and IL-1β expression was performed on bone marrow aspirates from each of the 13 patients. None of the neoplastic cells from the 11 patients with WM showed detectable IL-1β expression by ISH. However, the neoplastic cells from both patients with IgM MM expressed IL-1β mRNA at high levels. This aberrant IL-1β production may explain the presence of bone lesions in the patients with IgM MM.