Tumour-induced dysfunction of cytotoxic T cells in patients with multiple myeloma (MM) may contribute to immune escape and be responsible for the lack of therapeutic efficacy of immune checkpoint blockade. We therefore investigated dysfunctional clonal T cells in MM and demonstrated immunosenescence but not exhaustion as a predominant feature. T-cell clones were detected in 75% of MM patients and their prognostic significance was revalidated in a new post-immunomodulatory drug cohort. The cells exhibited a senescent secretory effector phenotype: KLRG-1+/CD57+/CD160+/CD28-. Normal-for-age telomere lengths indicate that senescence is telomere independent and potentially reversible. p38-mitogen-activated protein kinase, p16 and p21 signalling pathways known to induce senescence were not elevated. Telomerase activity was found to be elevated and this may explain how normal telomere lengths are maintained in senescent cells. T-cell receptor signalling checkpoints were normal but elevated SMAD levels associated with T-cell inactivation were detected and may provide a potential target for the reversal of clonal T-cell dysfunction in MM. Low programmed death 1 and cytotoxic T-lymphocyte-associated antigen 4 expression detected on T-cell clones infers that these cells are not exhausted but suggests that there would be a suboptimal response to immune checkpoint blockade in MM. Our data suggest that other immunostimulatory strategies are required in MM.

Despite improved outcomes in multiple myeloma (MM), a cure remains elusive. However, even before the current therapeutic era, 5% of patients survived >10 years and we propose that immune factors contribute to this longer survival. We identified patients attending our clinic, who had survived >10 years (n=20) and analysed their blood for the presence of T-cell clones, T-regulatory cells (Tregs) and T helper 17 (Th17) cells. These results were compared with MM patients with shorter follow-up and age-matched healthy control donors. The frequency of cytotoxic T-cell clonal expansions in patients with <10 years follow-up (MM patients) was 54% (n=144), whereas it was 100% (n=19/19) in the long-survivors (LTS-MM). T-cell clones from MM patients proliferated poorly in vitro, whereas those from LTS-MM patients proliferated readily (median proliferations 6.1% and 61.5%, respectively (P<0.0001)). In addition, we found significantly higher Th17 cells and lower Tregs in the LTS-MM group when compared with the MM group. These results indicate that long-term survival in MM is associated with a distinct immunological profile, which is consistent with decreased immune suppression.

Myeloid derived suppressor cells (MDSCs) are a heterogeneous population of cells that have been implicated as inhibitors of lymphopoiesis in patients with malignancies. They have a consensus phenotype of CD33+/CD11b+/HLA-DRlo/- and can be further divided into CD15 + granulocytic (G-MDSC) and CD14 + monocytic (M-MDSC) subsets. We characterized MDSCs in patients with multiple myeloma (MM) and found a significant increase in G-MDSCs in the blood of patients with progressive MM. Flow-sorted MDSCs from patients with MM induced the generation of regulatory T cells (Treg). MDSCs from both patients with MM and aged-matched controls demonstrated a dose-dependent inhibition of lymphocyte proliferation in carboxyfluorescein succinimidyl ester (CFSE)-tracking experiments. Granulocyte colony stimulating factor (G-CSF) administered to induce stem cell mobilization caused an increase in the number of MDSCs in the peripheral blood of patients with MM and a concentration of these immune-suppressive cells in peripheral blood stem cell collections. MDSCs are likely to cause immune dysfunction in patients with MM.

The transfer of membrane proteins between cells during contact, known as trogocytosis, can create novel cells with a unique phenotype and altered function. We demonstrate that trogocytosis is more common in multiple myeloma (MM) than chronic lymphocytic leukemia and Waldenstrom macroglobulinaemia; that T cells are more probable to be recipients than B or natural killer cells; that trogocytosis occurs independently of either the T-cell receptor or HLA compatibility; and that after trogocytosis, T cells with acquired antigens can become novel regulators of T-cell proliferation. We screened 168 patients with MM and found that CD86 and human leukocyte antigen G (HLA-G) were antigens commonly acquired by T cells from malignant plasma cells. CD3+CD86acq+ and CD3+ HLA-Gacq+ cells were more prevalent in bone marrow than peripheral blood samples. The presence of either CD86 or HLA-G on malignant plasma cells was associated with a poor prognosis. CD38++ side population cells expressed HLA-G, suggesting that these putative myeloma stem cells could generate immune tolerance. HLA-G+ T cells had a regulatory potency similar to natural Tregs, thus providing another novel mechanism for MM to avoid effective immune surveillance.

We have characterised the CD138⁻ PCs as more immature and with a significantly higher proliferative potential. The current trend to ignore this more immature and proliferative subpopulation of malignant PCs may have serious implications when determining gene expression, classifications and drug sensitivity of the malignancy.

This study demonstrated an increase in proapoptotic signaling during PLT storage, which was exacerbated by PRT. Many of these differences emerged outside the current 5-day storage period. These changes may not currently influence PLT transfusion quality, but will need to be carefully evaluated when considering extending PLT storage beyond 5 days.

Background: Regulated suppression of maternal Th1 immunity is necessary for normal pregnancy since inappropriate Th1 responses results in increased pregnancy loss and complications including intrauterine growth restriction (IUGR). We have shown that suppression of the p65 subunit of NF-κB in maternal T-cells underlies this change in T-cell responses. This study aimed to determine mechanism(s) that control p65 suppression.

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