ABSTRACT
T lymphocyte alterations are central to sepsis pathophysiology, whereas related mechanisms remain poorly understood. We hypothesized that metabolic alterations could play a role in sepsis-induced T lymphocyte dysfunction. Samples from septic shock patients were obtained at day 3 and compared with those from healthy donors. T cell metabolic status was evaluated in the basal condition and after T cell stimulation. We observed that basal metabolic content measured in lymphocytes by nuclear magnetic resonance spectroscopy was altered in septic patients. Basal ATP concentration, oxidative phosphorylation (OXPHOS), and glycolysis pathways in T cells were decreased as well. After stimulation, T lymphocytes from patients failed to induce glycolysis, OXPHOS, ATP production, GLUT1 expression, glucose entry, and proliferation to similar levels as controls. This was associated with significantly altered mTOR, but not Akt or HIF-1α, activation and only minor AMPKα phosphorylation dysfunction. IL-7 treatment improved mTOR activation, GLUT1 expression, and glucose entry in septic patients' T lymphocytes, leading to their enhanced proliferation. mTOR activation was central to this process, because rapamycin systematically inhibited the beneficial effect of recombinant human IL-7. We demonstrate the central role of immunometabolism and, in particular, mTOR alterations in the pathophysiology of sepsis-induced T cell alterations. Our results support the rationale for targeting metabolism in sepsis with recombinant human IL-7 as a treatment option.
Subject(s)
Glucose/metabolism , Immunotherapy/methods , Interleukin-7/immunology , Shock, Septic/immunology , T-Lymphocytes/immunology , TOR Serine-Threonine Kinases/metabolism , Adenosine Triphosphate/metabolism , Aged , Aged, 80 and over , Cell Proliferation/drug effects , Cells, Cultured , Energy Metabolism/drug effects , Female , Glucose Transporter Type 1/genetics , Glucose Transporter Type 1/metabolism , Glycolysis/drug effects , Humans , Interleukin-7/therapeutic use , Male , Middle Aged , Nuclear Magnetic Resonance, Biomolecular , Oxidative Phosphorylation/drug effects , Shock, Septic/therapy , Sirolimus/pharmacology , T-Lymphocytes/metabolismABSTRACT
Septic patients develop immune dysfunctions, the intensities and durations of which are associated with deleterious outcomes. LILRB2 (leukocyte immunoglobulin-like receptors subfamily B, member 2), an inhibitory member of the LILR family of receptors, is known for its immunoregulatory properties. In a microarray study, we identified LILRB2 as an upregulated gene in septic shock patients. On monocytes primed with LPS ex vivo, LILRB2 mRNA and protein expressions were dose-dependently downregulated and subsequently highly upregulated versus non-stimulated cells. This is concordant with clinical data, since both LILRB2 mRNA and protein expressions were significantly increased in septic shock patients at day 3. In a cohort of more than 700 patients, only after septic shock were LILRB2 mRNA levels increased compared with non-infected or less severely infected patients. This was preceded by a phase of downregulated mRNA expression during the first hours after septic shock. Interestingly, the intensity of this decrease was associated with increased risk of death after septic shock. LILRB2 protein and mRNA expressions are deregulated on monocytes after septic shock and this can be reproduced ex vivo after LPS challenge. Considering LILRB2 inhibitory properties, we can hypothesize that LILRB2 may participate in the altered immune response after septic shock.
Subject(s)
Membrane Glycoproteins/metabolism , Monocytes/immunology , RNA, Messenger/genetics , Receptors, Immunologic/metabolism , Shock, Septic/immunology , Aged , Aged, 80 and over , Cells, Cultured , Cohort Studies , Female , Gene Expression Regulation , Humans , Immunomodulation , Lipopolysaccharides/immunology , Male , Membrane Glycoproteins/genetics , Middle Aged , Receptors, Immunologic/genetics , Risk , Shock, Septic/mortality , Survival AnalysisABSTRACT
Severe injuries such as severe sepsis, burn, trauma and major surgery lead to an overlapping development of pro- and anti- inflammatory responses. It is now well established that these injuries are associated with the secondary development of immune suppression, which results in significant morbidity and mortality. Recent data suggest that immunostimulatory drugs might prevent these complications. However, intensive care patients are heterogeneous, making patient stratification essential for a targeted treatment. In the present review, we discuss potential biomarkers of injury-induced immunoparalysis, mainly focusing on these that have been associated with poor outcome in various clinical settings. We namely present clinical data on monocyte human leukocyte antigen DR, lymphopenia, PD-1/PD-L1 and transcriptomic approach.
ABSTRACT
In several clinical contexts, the measurement of ATP concentration in T lymphocytes has been proposed as a biomarker of immune status, predictive of secondary infections. However, the use of such biomarker in lymphopenic patients requires some adaptations in the ATP dosage protocol. We used blood from healthy volunteers to determine the optimal experimental settings. We investigated technical aspects such as the type of anticoagulant for blood sampling, the effect of freeze and thaw cycles, the reagent and sample mixing sequence, and the optimal dilution buffer. We also shortened the incubation time to 8h, and even showed that a 30min incubation may be sufficient. To evaluate the ATP rise upon lymphocyte activation, the optimal dose of stimulant was defined to be 4µg/mL of phytohaemagglutinin. Lastly, we determined that the number of T cells needed for this measurement was as low as 50,000, which is compatible with the existing lymphopenia in clinical settings. This optimized protocol appears ready to be assessed in lymphopenic patients to further investigate the interconnection between T lymphocyte metabolism and impaired phenotype and functions.
