Functionally Suppressive CD8 T Regulatory Cells Are Increased in Patients with Multiple Myeloma: A Cause for Immune Impairment

Abstract

BackgroundMultiple myeloma (MM) is a plasma cell malignancy frequently associated with impaired immune cell numbers and functions. In MM, several studies have previously shown that CD4 regulatory T (Treg) cells hamper effector T cell functions and enhance immune dysfunction. In this study, we aimed to prove the presence of functionally suppressive Treg cells expressing CD8 phenotype (CD8 Treg cells) in MM. To the best of our knowledge, this has not been reported previously in MM.MethodsWe analyzed CD8 Treg cells and their transcription factor FoxP3 from 64 newly diagnosed MM patients using flow cytometry and real time-polymerase chain reaction (RT-PCR). RNA profile of cytokines in CD8 Treg cells was also assessed using RT-PCR. CD8 Treg cells from 5 MM patients and 5 healthy donors were functionally evaluated using proliferation assays.ResultsCD8 Treg cells (CD8+CD25hi+) were significantly elevated in MM patients (P<0.0001), and their transcription factor FoxP3 expression was also higher in MM (P<0.0001) compared to healthy donors which was evidenced by flow cytometry and RT-PCR analyses. CD8 Treg cells negatively correlated with total lymphocyte count (P = 0.016). Functional studies revealed that CD8 Treg cells isolated from MM patients and healthy donors inhibited proliferation of CD4 T cells in a concentration dependent manner. In the presence of CD8 Treg cells in proliferation assays, level of IFN-γ was decreased but not IL-10. CD4 T cells from MM patients secreted abnormal level of IL-10 compared to healthy donors (P = 0.01) in proliferation assays without CD8 Treg cells. RNA profile of cytokines from CD8 Treg cells did not differ significantly between MM patients and healthy donors.ConclusionsThese findings show the presence of increased number of functionally suppressive CD8 Treg cells in MM patients. We believe that these suppressive CD8 Treg cells might enhance immune impairment and disease progression in MM.

Contribution of regulatory T cells to immunosuppression and disease progression in multiple myeloma patients

“…We were the first to demonstrate that the amount of CD8 + Tregs is significantly increased in MM patients as compared with healthy subjects. Similar to CD4 + Tregs, CD8 + Tregs expressed elevated levels of FOXP3, cytotoxic T lymphocyte antigen-4 (CTLA4) and CD62L, while exhibiting a CD127 −/dim+ phenotype 5 . RT-PCR data confirmed the deregulation of CD8 + Tregs in MM patients, clearly showing that these cells express higher levels of FOXP3 than their normal counterparts 5 .…”

“…Similar to CD4 + Tregs, CD8 + Tregs expressed elevated levels of FOXP3, cytotoxic T lymphocyte antigen-4 (CTLA4) and CD62L, while exhibiting a CD127 −/dim+ phenotype 5 . RT-PCR data confirmed the deregulation of CD8 + Tregs in MM patients, clearly showing that these cells express higher levels of FOXP3 than their normal counterparts 5 . Functional assays revealed that CD8 + Tregs isolated from both MM patients and healthy individuals inhibit the proliferation of CD4 + T cells as well as their ability to secrete IFNγ (but not interleukin-10, IL-10) in a concentration-dependent manner.…”

Dissecting the multiple myeloma-bone microenvironment reveals new therapeutic opportunities

“…Recently, a regulatory subset of CD8 + T-cells has been identified in myeloma patients, with the ability to suppress CD4 + T-cell proliferation via the secretion of IFN-γ [84]. The clinical role of this subset of T-cells is currently unknown, although they are believed to contribute to immune suppression in myeloma.…”

Preclinical validation of interleukin 6 as a therapeutic target in multiple myeloma

“…There is also circumstantial evidence suggesting that CD8 T cells may be able to block the MGUS-to-MM progression during tumor development as long as the incipient myeloma cells maintain sufficient antigen-presentation capability to cytotoxic CD8 T cells [127]. On the minus side, a report on a significant increase in the number of suppressive CD8 T cells in MM suggests that these cells may in fact contribute to both the local immune suppression in the TME and the systemic immune deficiency commonly seen in patients with myeloma [128]…”