Serum interleukin-10 in plasma-cell dyscrasias.

Serum levels of interleukin-10 (IL-10) were measured by enzyme-linked immunosorbent assay in 115 patients with multiple myeloma (MM) in various phases of the disease (68 at diagnosis, 22 in plateau phase, 22 in relapse), in 71 individuals with monoclonal gammopathy of undetermined significance (MGUS), and in 53 normal volunteers. Detectable levels of serum IL-10 were found in 24 myelomas (20.9%), in 7 cases of MGUS (9.9%), and in 4 normal subjects (7.5%) (P = NS, chi2 test). In patients with MM, cytokine was detected with a comparable frequency in all pathologic stages and phases of the disease: 4/19 in stage I, 6/26 in stage II, 5/23 in stage III, 4/22 in plateau phase, and 5/25 in progressing or relapsed disease. IL-10 concentrations did not differ significantly between controls and patients with plasma-cell dyscrasia, between patients with MGUS and those with MM, between early vs. advanced MM, or between patients in different phases of the disease. In 36 patients with MM in whom IL-10 was measured serially, no significant changes were observed over the course of the disease. Also, when comparing the outcomes of individuals with detectable or undetectable IL-10 in single stages or in the whole myeloma group, no differences were revealed. Our results do not support an apparent involvement of IL-10 in the pathogenesis of MM in vivo. However, further studies are required to define the exact role of this cytokine within the complex cytokine network of this neoplastic disorder.