The role of lymphocyte apoptosis in septic shock remains a controversial issue. Using Annexin V and flow cytometry analysis on freshly isolated cells, we evaluated circulating lymphocyte apoptosis in 23 septic shock, 25 sepsis without shock, 7 nonseptic critically ill, and 25 control patients. In patients with sepsis, we compared day 1 lymphocyte apoptosis (i.e., within 3 days of the onset of infection) with that observed 5–7 days after (day 6) according to shock state, mortality, and severity factors. At day 1, patients in septic shock exhibited higher lymphocyte apoptosis than that present in controls (16.5% ± 3.5% vs. 3% ± 0.5%, respectively, P = 0.0001). At day 6, patients with sepsis without shock restored undamaged CD4⁺T and CD8⁺T lymphocyte counts, whereas patients in septic shock increased only CD4⁺T cells. Similarly, survivors restored undamaged lymphocyte count at day 6 (+70%, P < 0.001), whereas nonsurvivors did not. Day 6 undamaged lymphocyte count negatively correlated with day 1 SAPS II, day 6 LOD score, mechanical ventilation, and ICU stay duration. We observed no apoptotic effect of septic shock plasma or septic shock circulating mononuclear cells on target lymphoid cell lines. We found no alteration in any death receptors Fas, TRAIL-R1, TRAIL-R2, or in their ligands on circulating blood cells. Catecholamines and interleukin 10 levels significantly increased in patients with septic shock, but did not correlate with apoptosis levels. We conclude that lymphocyte apoptosis is rapidly increased in blood of patients in septic shock and that lymphocyte apoptosis leads to a profound and persistent lymphopenia associated with poor outcome. These results suggest that lymphocyte apoptosis is one of the main components of human septic shock immune dysfunction and could be related more to microcirculatory disturbance than to circulating factors.

The dosage of soluble programmed cell death ligand 1 (sPD-L1) protein in the blood of adults with cancer has never been performed in a prospective patient cohort. We evaluated the clinical impact of sPD-L1 level measured at the time of diagnosis for newly diagnosed diffuse large B-cell lymphoma (DLBCL). Soluble PD-L1 was measured in the plasma of 288 patients enrolled in a multicenter, randomized phase III trial that compared R-high-dose chemotherapy with R-CHOP. The median follow-up was 41.4 months. A cutoff of 1.52 ng/ml of PD-L1 level was determined and related to overall survival (OS). Patients with elevated sPD-L1 experienced a poorer prognosis with a 3-year OS of 76% versus 89% (P<0.001). Considering clinical characteristics, the multivariate analysis retained this biomarker besides bone marrow involvement and abnormal lymphocyte–monocyte score as independently related to poor outcome. sPD-L1 was detectable in the plasma and not in the serum, found elevated in patients at diagnosis compared with healthy subjects and its level dropped back to normal value after CR. The intention-to-treat analysis showed that elevated sPD-L1 was associated with a poorer prognosis for patients randomized within the R-CHOP arm (P<0.001). Plasma PD-L1 protein is a potent predicting biomarker in DLBCL and may indicate usefulness of alternative therapeutic strategies using PD-1 axis inhibitors.

Rationale: Sepsis induces a sustained immune dysfunction responsible for poor outcome and nosocomial infections. Myeloid-derived suppressor cells (MDSCs) described in cancer and inflammatory processes may be involved in sepsis-induced immune suppression but their clinical impact remains poorly defined. Objectives: To clarify phenotype, suppressive activity, origin, and clinical impact of MDSCs in septic patients. Methods: Peripheral blood transcriptomic analysis was performed on 29 septic patients and 15 healthy donors. A second cohort of 94 consecutive septic patients, 11 severity-matched intensive care patients and 67 healthy donors was prospectively enrolled for flow cytometry and functional experiments. Measurements and Main Results: Genes involved in MDSC suppressive functions, including S100A12, S100A9, MMP8 and ARG1, were upregulated in the peripheral blood of septic patients. CD14^posHLA-DR^low/neg monocytic (M)-MDSCs were expanded in intensive care septic and non-septic patients and CD14^negCD15^pos low-density granulocytes/ granulocytic (G)-MDSCs were more specifically expanded in septic patients (p<.001). Plasma levels of MDSC mediators S100A8/A9, S100A12, and Arginase 1 were significantly increased. In vitro, CD14^pos- and CD15^pos-cell depletion increased T-cell proliferation in septic patients. G-MDSCs, made of immature and mature granulocytes expressing high levels of degranulation markers, were specifically responsible for arginase 1 activity. High initial levels of G-MDSCs, arginase 1, and S100A12 but not M-MDSCs were associated with subsequent occurrence of nosocomial infections. Conclusions: M-MDSCs and G-MDSCs strongly contribute to T-cell dysfunction in septic patients. More specifically, G-MDSCs producing arginase 1 are associated with a higher incidence of nosocomial infections and appear to be major actors of sepsis-induced immune suppression.

In diffuse large B-cell lymphoma (DLBCL), the number of circulating monocytes and neutrophils represents an independent prognostic factor. These cell subsets include monocytic and granulocytic myeloid derived suppressor cells (M- and G-MDSCs) defined by their ability to suppress T-cell responses. MDSCs are a heterogeneous population described in inflammatory and infectious diseases as well as in numerous tumors including multiple myeloma, chronic lymphocytic leukemia and DLBCL. However, their mechanisms of action remain unclear. We broadly assessed the presence and mechanisms of suppression of MDSC subsets in DLBCL. First, a myeloid suppressive signature was identified by gene expression profiling in DLBCL peripheral blood. Accordingly, we identified in a cohort of 66 DLBCL patients an increase in circulating G-MDSC (Lin^negHLA-DR^negCD33^posCD11b^pos) and M-MDSC (CD14^posHLA-DR^low) counts. Interestingly, only M-MDSC number was correlated with the International Prognostic Index (IPI), the event-free survival (EFS), and the number of circulating T_reg. Furthermore, T-cell proliferation was restored after monocyte depletion. Myeloid-dependent T-cell suppression was attributed to a release of IL-10 and S100A12 and an increased PD-L1 expression. In summary, we identified expanded MDSC subsets in DLBCL as well as new mechanisms of immunosuppression in DLBCL.

Monocyte deactivation has been identified as a major factor of immunosuppression in sepsis and is associated with a loss of surface human leukocyte antigen–DR (HLA-DR) expression on circulating monocytes. Using flow cytometry, quantitative reverse transcription-polymerase chain reaction, we investigated this phenomenon in septic patients. We confirmed the early loss of monocyte HLA-DR expression in all infected patients and demonstrated that this persistent lowered expression at Day 6 correlated with severity scores, secondary infection, and death. This phenomenon occurred at a transcriptional level via a decrease in the class II transactivator A (CIITA) transcription. Furthermore, these abnormalities correlated with the high cortisol levels observed in sepsis and not with those of other putative factors such as catecholamines or interleukin-10. Finally, in vitro studies evidenced that glucocorticoids decrease HLA-DR expression at a transcriptional level via a decrease in CIITA mRNA levels, mainly by down modulating its isoforms I and III. We conclude that in human sepsis, the loss of HLA-DR expression on circulating monocytes is associated with a poor outcome. We suggest that the high endogenous cortisol level observed in septic shock may be a possible new factor involved in the loss of HLA-DR expression on monocytes via its effect on HLA-DR and CIITA transcription.