Human granulocytic myeloid-derived suppressor cells (G-MDSCs) have been described as low-density immunosuppressive CD66b+CD33dimHLA-DR-granulocytes that co-purify with mononuclear cells after density gradient centrifugation of blood from cancer patients. The role of G-MDSCs in Hodgkin (HL) and non-Hodgkin lymphoma (NHL) remains unclear.The percentage and immunophenotype of CD66b+CD33dimHLA-DR-cells were analyzed in PBMCs from HL and B-cell NHL patients (n = 124) and healthy donors (n = 48). The immunosuppressive functions of these cells were tested in vitro. Correlations between CD66b+CD33dimHLA-DR-cells and patient clinicopathological features and outcome, were evaluated.CD66b+CD33dimHLA-DR-cells were increased in PBMCs from HL and B-cell NHL patients as compared to healthy donors: 2.18 (0.02–70.92) vs 0.42 (0.04–2.97), p < 0.0001. Their percentage remained significantly higher even considering HL (n = 31), indolent (n = 31) and aggressive (n = 62) B-cell NHL patients separately: 1.54 (0.28–26.34), 2.15 (0.02–20.08), and 2.96 (0.25–70.92), respectively, p < 0.0001. CD66b+CD33dimHLA-DR-cells in patient PBMCs were mostly composed of mature CD11b+CD16+ low-density neutrophils in an activated status, as revealed by their higher CD11b and CD66b expression as compared to conventionally isolated (normal-density) autologous or healthy donor neutrophils. The in vitro depletion of CD66b+ cells from patient PBMCs restored the proliferation of autologous T cells. Higher frequencies of CD66b+CD33dimHLA-DR− G-MDSCs correlated significantly with unfavorable prognostic index scores and a shorter freedom from disease progression.PBMCs from HL and B-cell NHL patients contain a population of CD66b+CD33dimHLA-DR− G-MDSCs, mostly composed of activated low-density neutrophils with immunosuppressive properties. These findings disclose a previously unknown G-MDSC-mediated mechanism of immune-escape in lymphomas, therefore anticipating possible targets for therapeutic interventions.

Letter to the Editor Relapse of thrombotic thrombocytopenic purpura after COVID-19 vaccineWe report a case of a 48-year-old white female patient with a history of relapsing thrombotic thrombocytopenic purpura (TTP). The patient has been known to our department since 2015 when she was diagnosed for the first time with TTP with a high antibody titer (99 U/mL) against ADAMTS13 (A Disintegrin And MeTalloproteinase with a Thrombo-Spondin type 1 motif, member 13) and very low ADAMTS13 activity (Fluorescent Resonance Energy Transfer [FRET] assay: <3 %, normal range 45-138 %). She was treated with ten plasma-exchange (PEX) procedures and corticosteroids and obtained a complete remission. Her first relapse, in February 2019, presented as ecchymoses and severe thrombocytopenia; she was successfully treated again with seven PEX procedures and steroids. Afterwards, the patient was well and periodic blood cell counts (every 6 months, last check performed in October 2020) were normal. On March 12, 2021 the patient was referred to the emergency room of the city hospital of Mantua for a new onset of ecchymoses on both arms and forearms without any other symptoms or signs. The complete blood count demonstrated mild normocytic anemia (hemoglobin 11.5 g/dL, normal range 12.3-14.5 g/dL), moderate thrombocypenia (platelet count 94 × 10 9 /L, normal range 150− 400 × 10 9 /L), a coagulation profile and renal function within the normal range, and moderately increased lactate dehydrogenase (LDH, 637 UI/L, normal range 150-450 UI/L). On a peripheral blood smear, there were about 10 % schistocytes. ADAMTS13 activity was markedly reduced (FRET assay: <3 %) with a high titer of anti-ADAMTS13 antibodies (88 U/mL). Six days before the TTP relapse (March 6, 2021), the patient had received the second dose of the anti-COVID-19 vaccine produced by Pfizer-BioNTech (the first dose had been administered on February 11, 2021). At hospital admission the molecular search of SARS-COV-2 on nasopharyngeal swab was negative while anti-SARS-COV-2 IgG antibodies were 105 UA/mL (chemiluminescent immunoassay DiaSorin, positive >15 UA/mL). The patient was promptly treated with seven PEX procedures and steroids, with a rapid and excellent response (normalization of platelet count and LDH after the third PEX). This is the first case reported in literature of a TTP relapse following anti-COVID-19 vaccination. Other cases of vaccine-related thrombotic microangiopathies have been described, possibly related to the immune dysregulation and/or complement activation triggered by vaccination, particularly against influenza [1][2][3][4]. Further studies are needed to verify the possible association between microangiopathic thrombotic disorders with an autoimmune pathogenesis and the administration of vaccines against COVID-19. ContributionC.S. and A.A.

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Notch3 and Notch4 support survival of primary B-cell acute lymphoblastic leukemia (B-ALL) cells, suggesting a role for Notch signaling in drug response. Here we used in vitro, in silico, and in vivo mouse xenograft model-based approaches to define the role of the Notch pathway in BALL chemosensitivity. We observed significant Notch receptor and ligand expression in BALL primary cells and cell lines. Primary leukemia cells from high-risk patients overexpressed Notch3, Notch4, and Jagged2 while displaying a reduction in expression levels of Notch1-4 following chemotherapy. We then analyzed in vitro cell survival of BALL cells treated with conventional chemotherapeutic agents alone or in combination with Notch signaling inhibitors. Gamma-secretase inhibitors (GSI) and anti-Notch4 were all capable of potentiating drug-induced cell death in BALL cells by upregulating intracellular levels of reactive oxygen species, which in turn modulated mTOR, NF-kB, and ERK expression. In NOG-mouse-based xenograft models of BALL , co-administration of the Notch inhibitor GSI-XII with the chemotherapeutic agent Ara-C lowered bone marrow leukemic burden compared with DMSO or Ara-C alone, thus prolonging mouse survival. Overall, our results support the potential effectiveness of Notch inhibitors in patients with BALL. Significance: Inhibition of Notch signaling enhances the chemosensitivity of BALL cells, suggesting Notch inhibition as a potential therapeutic strategy to improve the outcome of patients with BALL .

B-cell receptor (BCR) signaling is a key determinant of variable clinical behavior and a target for therapeutic interventions in chronic lymphocytic leukemia (CLL). Endogenously produced HO is thought to fine-tune the BCR signaling by reversibly inhibiting phosphatases. However, little is known about how CLL cells sense and respond to such redox cues and what effect they have on CLL. We characterized the response of BCR signaling proteins to exogenous HO in cells from patients with CLL, using phosphospecific flow cytometry. Exogenous HO in the absence of BCR engagement induced a signaling response of BCR proteins that was higher in CLL with favorable prognostic parameters and an indolent clinical course. We identified low expression as a possible mechanism accounting for redox signaling hypersensitivity. Decreased catalase could cause an escalated accumulation of exogenous HO in leukemic cells with a consequent greater inhibition of phosphatases and an increase of redox signaling sensitivity. Moreover, lower levels of were significantly associated with a slower progression of the disease. In leukemic cells characterized by redox hypersensitivity, we also documented an elevated accumulation of ROS and an increased mitochondrial amount. Taken together, our data identified redox sensitivity and metabolic profiles that are linked to differential clinical behavior in CLL. This study advances our understanding of the redox and signaling heterogeneity of CLL and provides the rationale for the development of therapies targeting redox pathways in CLL.