CD4⁺CD25⁺FoxP3⁺regulatory T cells are increased whilst CD3⁺CD4⁻CD8⁻αβTCR⁺Double Negative T cells are decreased in the peripheral blood of patients with multiple myeloma which correlates with disease burden

Summary Increased levels of naturally occurring regulatory T cells (T Reg cells) have been found in a variety of solid tumours and haematological malignancies. In multiple myeloma (MM), evidence suggests that T Reg cells are increased though controversy exists with regards to their function and no relationship to disease stage and treatment has been demonstrated. Here, we demonstrate significantly elevated levels of functional CD4 + CD25 + FoxP3 + T Reg cells in a large cohort of patients with MM as well as monoclonal gammopathy of uncertain significance (MGUS) in comparison to age‐matched, healthy controls. The frequency of Double Negative T Reg cells was also evaluated, demonstrating that these cells were reduced in patients with MM. Furthermore, a characteristic profile of immunomodulatory cytokines in the peripheral blood and bone marrow of patients with MM and MGUS was demonstrated, compared with healthy controls. This data adds further evidence to the understanding of the role of T Reg cell subsets in tumour immunology and the fundamentals of the host/tumour immune conflict.