Hierarchical Involvement of Myeloid-Derived Suppressor Cells and Monocytes Expressing Latency-Associated Peptide in Plasma Cell Dyscrasias

Abstract

Objective: Plasma cell dyscrasias (PCDs) are disorders of plasma cells having in common the production of a monoclonal M-protein. They include a spectrum of conditions that may represent a natural progression of the same disease from monoclonal gammopathy of unknown significance to asymptomatic and symptomatic multiple myeloma, plasma cell leukemia, and Waldenström's macroglobulinemia. In PCDs, the immune system is actively suppressed through the secretion of suppressive factors and the recruitment of immune suppressive subpopulations. In this study, we examined the expression of two subpopulations of cells with immunosuppressive activity, monocytic myeloid-derived suppressor cells (MDSCs) and monocytes expressing latency-associated peptide (LAP), in patients with different PCDs and in healthy volunteers. Materials and Methods: A total of 27 consecutive patients with PCDs were included in this study. Nineteen healthy volunteers served as controls. Results: We observed a hierarchical correlation between disease activity and the presence of monocytes with immunosuppressive activity. Conclusion: These results suggest that MDSCs and monocytes expressing LAP have diverging roles in PCDs and may perhaps serve as biomarkers of tumor activity and bulk.

Keywords

• multiple myeloma
• monoclonal gammopathy of unknown significance
• myeloid-derived suppressor cells
• latency-associated peptide