Tumour necrosis factor-α and interleukin 4 promote the differentiation of myeloma cell precursors in multiple myeloma

Summary. The effects of tumour necrosis factor-α (TNF-α) and interleukin 4 (IL-4) on peripheral blood mononuclear cells (PBMC) from 36 patients with multiple myeloma (MM), 12 with monoclonal gammopathy of undetermined significance (MGUS) and 21 normal controls, were investigated. In 16/36 patients with MM, monoclonal plasma cells appeared after 4d in cultures containing TNF-α and IL-4. These changes were not observed in PBMC from patients with MGUS or from normal controls. These findings suggest that myeloma cell precursors do exist in the peripheral blood of MM patients and differentiate into plasma cells in the presence of TNF-α and IL-4. Based on these observations, we think that the variation in the number of myeloma cell precursors in peripheral blood could be used as a prognostic parameter of response to chemotherapy in myeloma patients. In addition, this assay may be useful to distinguish early-stage MM from MGUS.