Septic syndrome is the leading cause of mortality for critically ill patients worldwide. Patients develop lymphocyte dysfunctions associated with increased risk of death and nosocomial infections. In this study, we performed preclinical experiments testing the potential of recombinant human IL-7 (rhIL-7) as a lymphostimulating therapy in sepsis. Circulating IL-7 and soluble IL-7 receptor α-chain (soluble CD127) concentrations were measured in plasma, whereas cellular CD127 expression was evaluated on circulating CD4+ and CD8+ lymphocytes from septic shock patients and healthy volunteers. Lymphocyte proliferation, IFN-γ production, STAT5 phosphorylation, and B cell lymphoma 2 induction were measured ex vivo in response to T cell stimulation in the presence or not of rhIL-7. We show that IL-7 pathway (plasmatic IL-7 concentration and cellular and soluble CD127 expressions) is not overtly altered and remains activable in septic patients. Most importantly ex vivo treatment of patients’ cells with rhIL-7 significantly improves lymphocyte functionality (CD4+ and CD8+ lymphocyte proliferations, IFN-γ production, STAT5 phosphorylation, and B cell lymphoma 2 induction after stimulation). To our knowledge, this constitutes the first report of rhIL-7 ability to restore normal lymphocyte functions in septic patients. These results support the rational for initiating a clinical trial testing rhIL-7 in septic shock.

A dramatic decrease in circulating lymphocyte number is regularly described after septic shock. However, it is unknown how early this alteration develops after diagnosis of shock and if it remains stable over time. Twenty-one septic shock patients with no comorbidities were included within 2 h after the beginning of vasopressive treatment. Flow cytometry phenotyping of circulating leukocyte subpopulations and quantitative real-time polymerase chain reaction of T-bet, GATA-3, FOXP3, and RORγ mRNA were performed in patients from the diagnosis of shock and every 6 h during the subsequent 48 h. From their admission in the intensive care unit, patients present with major alterations of circulating leukocyte count (leukocytosis, neutrophilia, and major lymphopenia). The numbers of every lymphocyte subpopulations (T, B, and natural killer cells) were diminished. Gene expression analysis of transcription factors specific for TH1, TH2, CD4CD25 regulatory, and TH17 lymphocytes showed a severe decrease in comparison with healthy individuals' values. These alterations remain stable during the first 48 h after inclusion in the protocol despite early and aggressive resuscitation and antibiotherapy administered in patients. At the time of diagnosis of shock and admission in the intensive care unit, septic patients already present with severe lymphopenia involving every lymphocyte subsets including CD4 T-cell subpopulations. No significant variation could be detected within the first 48 h. This should be taken into account in the forthcoming clinical trials testing immunomodulating therapies in septic shock patients.

Severe septic syndromes deeply impair innate and adaptive immunity and are responsible for sepsis-induced immunosuppression. Although neutrophils represent the first line of defense against infection, little is known about their phenotype and functions a few days after sepsis, when the immunosuppressive phase is maximal (i.e., between d 3 and 8). The objective of the present study was to perform, for the first time, a global evaluation of neutrophil alterations in immunosuppressed septic patients (at d 3-4 and d 6-8) using phenotypic and functional studies. In addition, the potential association of these parameters and deleterious outcomes was assessed. Peripheral blood was collected from 43 septic shock patients and compared with that of 23 healthy controls. In the septic patients, our results highlight a markedly altered neutrophil chemotaxis (functional and chemokine receptor expressions), oxidative burst, and lactoferrin content and an increased number of circulating immature granulocytes (i.e., CD10(dim)CD16(dim)). These aspects were associated with an increased risk of death after septic shock. In contrast, phagocytosis and activation capacities were conserved. To conclude, circulating neutrophils present with phenotypic, functional, and morphologic alterations a few days after sepsis onset. These dysfunctions might participate in the deleterious role of sepsis-induced immunosuppression. The present results open new perspectives in the mechanisms favoring nosocomial infections after septic shock. They deserve to be further investigated in a larger clinical study and in animal models recapitulating these alterations.

SummaryWe report the post‐transplant lymphocyte subset recovery of 226 children treated with Unrelated Cord Blood transplant (UCBT) (n = 112) or Unrelated Bone Marrow Transplant (UBMT) (n = 114) for malignant or non‐malignant diseases. Absolute numbers of natural killer (NK), B and T cells were monitored by flow cytometry up to 5 years post‐transplant. Immunological endpoints were: time to achieve a CD3+ cell count >0·5 and 1·5 × 109/l, CD4+ > 0·2 and 0·5 × 109/l, CD8+ > 0·25 × 109/l, CD19+ > 0·2 × 109/l, NK > 0·1 × 109/l. These endpoints were analysed through the use of cumulative incidence curves in the context of competing risks. CD8+ T cell recovery was delayed after UCBT with a median time to reach CD8+ T cells > 0·25 × 109/l of 7·7 months whereas it was 2·8 months in UBMT (P < 0·001). B cell recovery was better in UCBT, with a median time to reach CD19+ cells > 0·2 × 109/l of 3·2 months in UCBT and 6·4 months in UBMT (P = 0·03). Median time for CD4+ T cell and NK cell recovery was similar in UCBT and UBMT. CD4+ T cells recovery was negatively correlated to age (better reconstitution in younger patients, P = 0·002). CD8+ T cells recovery was shorter in recipients with a positive cytomegalovirus serology (P = 0·001).

Septic shock is accompanied by the development of immune dysfunctions whose intensity and duration are associated with increased risk of secondary infections and mortality. Although B lymphocytes play a pivotal role in the immune response to infections, no comprehensive exploration of circulating B cell status has been performed during the immunosuppressive phase of septic shock. Thus, our aim was to extensively characterize the phenotype and function of B cells in septic shock, including IL-10 production. Circulating B lymphocyte phenotype and function were evaluated by flow cytometry on fresh whole blood and after ex vivo stimulation in adult septic shock patients sampled at day 1, 3, and 6 after the onset of shock. The circulating B cell number was reduced in septic shock patients, whereas the B cell proportion among total lymphocytes was increased. The remaining circulating B lymphocytes presented with decreased MHC class II expression and increased CD21 CD95 exhausted-like phenotype but showed no change in maturation status. Circulating B cell functions were markedly altered after sepsis with reduced ex vivo activation and proliferation capacities. Finally, B cell response after septic shock was characterized by a clear plasmacytosis and an increased IL-10 production in remaining B cells from patients after ex vivo stimulation. During the sepsis-induced immunosuppression phase, B cell response is altered and is oriented toward an exhausted-like/immunoregulatory profile. Further studies are now needed to confirm the immunoregulatory properties of B lymphocytes and evaluate their role in sepsis-induced immunosuppression.