Adult survivors of invasive pneumococcal disease exhibit defective B cell function

Contact dependent suppression of CD4 T cell activation and proliferation by B cells activated through IgD cross-linking

Although the co-stimulatory interaction between B and T cells is well defined, recent evidence suggests that B cells also have a regulatory role. Here, we show that B cells activated using anti-IgD conjugated to dextran (α-δ-dex) directly inhibit TCR-induced CD4 T cell activation, proliferation and cytokine production. This effect was observed in CD4 T cells activated both with and without CD28 co-stimulation. T cell viability was unaffected, and the T cell suppressive effect was mediated by contact with IgD activated purified B cells and not by IL-10 or other soluble factors. This is the first evidence of IgD activated B cells mediating inhibition of activation and proliferation of CD4 T cells in humans. This article is protected by copyright. All rights reserved.

Role of circulating lymphocytes in patients with sepsis

Sepsis is a systemic inflammatory response syndrome due to infection. The incidence rate is estimated to be up to 19 million cases worldwide per year and the number of cases is rising. Infection triggers a complex and prolonged host response, in which both the innate and adaptive immune response are involved. The disturbance of immune system cells plays a key role in the induction of abnormal levels of immunoregulatory molecules. Furthermore, the involvement of effector immune system cells also impairs the host response to the infective agents and tissue damage. Recently, postmortem studies of patients who died of sepsis have provided important insights into why septic patients die and showed an extensive depletion of CD4 and CD8 lymphocytes and they found that circulating blood cells showed similar findings. Thus, the knowledge of the characterization of circulating lymphocyte abnormalities is relevant for the understanding of the sepsis pathophysiology. In addition, monitoring the immune response in sepsis, including circulating lymphocyte subsets count, appears to be potential biomarker for predicting the clinical outcome of the patient. This paper analyzes the lymphocyte involvement and dysfunction found in patients with sepsis and new opportunities to prevent sepsis and guide therapeutic intervention have been revealed.

Early alterations of B cells in patients with septic shock

Introduction

It has recently been proposed that B lymphocytes are involved in sepsis pathogenesis. The goal of this study is to investigate potential abnormalities in a subset distribution and activation of circulating B lymphocytes in patients with septic shock.

Methods

This observational prospective study was conducted in a medical-surgical ICU. All patients with septic shock were eligible for inclusion. B-cell phenotypes (CD19+CD69+, CD19+CD23+, CD19+CD5+, CD19+CD80, CD19+CD86+, CD19+CD40 and CD19+CD95+) were assessed by quantitative flow cytometry upon admission to the ICU and 3, 7, 14 and 28 d later.

Results

Fifty-two patients were included. Thirty-six healthy volunteers matched for age and sex were used as controls. The patients had lymphopenia that was maintained during 28 d of follow-up. In patients with septic shock who died, the percentage of CD19+CD23+ was lower during the 7 d of follow-up than it was in survival patients. Moreover, the percentage of CD80+ and CD95+ expression on B cells was higher in patients who died than in survivors. Receiver operating characteristic curve analysis showed that a CD19+CD23+ value of 64.6% at ICU admission enabled discrimination between survivors and nonsurvivors with a sensitivity of 90.9% and a specificity of 80.0% (P = 0.0001).

Conclusions

Patients with septic shock who survive and those who don't have different patterns of abnormalities in circulating B lymphocytes. At ICU admission, a low percentage of CD23+ and a high of CD80+ and CD95+ on B cells were associated with increased mortality of patients with septic shock. Moreover, a drop in circulating B cells persisted during 28 d of ICU follow-up.

Correlation of group C meningococcal conjugate vaccine response with B- and T-lymphocyte activity

Despite the success of conjugate vaccination against meningococcal group C (MenC) disease, post-vaccination, some individuals still exhibit rapid waning of initially protective bactericidal antibody levels. The mechanism of this relative loss of humoral protection remains undetermined. In this report we have investigated the relationship between T- and B-cell activation and co-stimulation and the loss of protective antibody titers. We have found that healthy volunteers who lose protective MenC antibody levels one year after receipt of glycoconjugate vaccine exhibit no detectable cellular defect in polyclonal B- or T-cell activation, proliferation or the B-memory pool. This suggests that the processes underlying the more rapid loss of antibody levels are independent of defects in either initial T- or B-cell activation.