Expression of the serpin serine protease inhibitor 6 protects dendritic cells from cytotoxic T lymphocyte-induced apoptosis: differential modulation by T helper type 1 and type 2 cells

Dendritic cells (DCs) play a central role in the immune system as they drive activation of T lymphocytes by cognate interactions. However, as DCs express high levels of major histocompatibility complex class I, this intimate contact may also result in elimination of DCs by activated cytotoxic T lymphocytes (CTLs) and thereby limit induction of immunity. We show here that immature DCs are indeed susceptible to CTL-induced killing, but become resistant upon maturation with anti-CD40 or lipopolysaccharide. Protection is achieved by expression of serine protease inhibitor (SPI)-6, a member of the serpin family that specifically inactivates granzyme B and thereby blocks CTL-induced apoptosis. Anti-CD40 and LPS-induced SPI-6 expression is sustained for long periods of time, suggesting a role for SPI-6 in the longevity of DCs. Importantly, T helper 1 cells, which mature DCs and boost CTL immunity, induce SPI-6 expression and subsequent DC resistance. In contrast, T helper 2 cells neither induce SPI-6 nor convey protection, despite the fact that they trigger DC maturation with comparable efficiency. Our data identify SPI-6 as a novel marker for DC function, which protects DCs against CTL-induced apoptosis.     

Classification, functions, and clinical relevance of extracellular vesicles

Both eukaryotic and prokaryotic cells release small, phospholipid-enclosed vesicles into their environment. Why do cells release vesicles? Initial studies showed that eukaryotic vesicles are used to remove obsolete cellular molecules. Although this release of vesicles is beneficial to the cell, the vesicles can also be a danger to their environment, for instance in blood, where vesicles can provide a surface supporting coagulation. Evidence is accumulating that vesicles are cargo containers used by eukaryotic cells to exchange biomolecules as transmembrane receptors and genetic information. Because also bacteria communicate to each other via extracellular vesicles, the intercellular communication via extracellular cargo carriers seems to be conserved throughout evolution, and therefore vesicles are likely to be a highly efficient, robust, and economic manner of exchanging information between cells. Furthermore, vesicles protect cells from accumulation of waste or drugs, they contribute to physiology and pathology, and they have a myriad of potential clinical applications, ranging from biomarkers to anticancer therapy. Because vesicles may pass the blood-brain barrier, they can perhaps even be considered naturally occurring liposomes. Unfortunately, pathways of vesicle release and vesicles themselves are also being used by tumors and infectious diseases to facilitate spreading, and to escape from immune surveillance. In this review, the different types, nomenclature, functions, and clinical relevance of vesicles will be discussed.     

Efficient ways exist to obtain the optimal sample size in clinical trials in rare diseases

OBJECTIVE: Recruitment of pediatric patients in randomized clinical trials is hampered by the rarity of many conditions and by ethical constraints. The objective of this paper is to give an overview of design options to obtain a statistically valid result while including a minimum number of subjects. STUDY DESIGN AND SETTING: Overview and discussion of several approaches to conduct valid randomized clinical trials in rare diseases and vulnerable populations. RESULTS: Sequential designs have been developed as efficient ways to evaluate accumulating information from a clinical trial, thereby reducing the average size of trials. Different sequential procedures exist, including group sequential designs, boundaries designs, and adaptive designs. The sample size attained at the end of the trial is unknown at the start. The sample size for a given set of alpha, beta, and effect size may turn out to be larger than with a classical fixed sample size approach. Simulations have shown that on average, sample sizes are smaller. CONCLUSION: There are several possibilities to optimize the number of subjects in a clinical trial. The rarity of many disorders in children and the ethical requirements in this patient population should not obstruct the performance of well-designed research to support clinical decision making.     

Biomechanics of slow running and walking with a rocker shoe

Evidence suggests a link between the loading of the Achilles tendon and the magnitude of the ankle internal plantar flexion moment during late stance of gait, which is clinically relevant in the management of Achilles tendinopathy. Some studies showed that rocker shoes can reduce the ankle internal plantar flexion moment. However, the existing evidence is not conclusive and focused on walking and scarce in running. Sixteen healthy runners participated in this study. Lower extremity kinetics, kinematics and electromyographic (EMG) signals of triceps surae and tibialis anterior were quantified for two types of shoes during running and walking. The peak ankle plantar flexion moment was reduced significantly in late stance of running (0.27 Nm/kg; p < 0.001) and walking (0.24 Nm/kg; p < 0.001) with the rocker shoe compared to standard shoe. The ankle power generation and plantar flexion moment impulse were also reduced significantly when running and walking with the rocker shoe (p < 0.001). No significant changes in the knee and hip moments were found in running and walking. A significant delay of the EMG peak, approximately 2% (p < 0.001), was present in the triceps surae when walking with rocker shoes. There were no significant changes in the EMG peak amplitude of triceps surae in running and walking. The peak amplitude of tibialis anterior was significantly increased (64.7 μV, p < 0.001) when walking with rocker shoes. The findings show that rocker shoes reduce the ankle plantar flexion moment during the late stance phase of running and walking in healthy people.     

Splenectomy in children with idiopathic thrombocytopenic purpura: A prospective study of 134 children from the Intercontinental Childhood ITP Study Group

BACKGROUND: Splenectomy is an effective procedure for children and adults with severe or refractory idiopathic thrombocytopenic purpura (ITP). Data regarding pediatric patients are limited. PROCEDURE: Sixty-eight Intercontinental Childhood ITP Study Group (ICIS) investigators from 57 institutions in 25 countries participated in a splenectomy registry. Data from 153 patients were submitted, of whom 134 had a splenectomy and were analyzed. RESULTS: The median age at splenectomy was 11.8 (2.7-20.7) years. The median postsplenectomy follow-up was 2.0 (0.1-4.5) years. Pre-splenectomy vaccination was not administered in 21 children (15.7%). Open and laparoscopic splenectomy procedures were performed in 67 and 65 evaluable children, respectively. Surgical technique was not reported in two children. Overall immediate platelet response to splenectomy was achieved in 113 patients (86.3%). Eighty percent of responders maintained their status of response during the following 4 years. Older age, longer duration of ITP, and male gender correlated with a complete response. Post-splenectomy sepsis was reported in seven patients without lethal outcome, although sepsis might be differently defined at participating institutions. CONCLUSIONS: Splenectomy is effective in children with ITP. Management varies greatly in different institutions. These Registry data may serve as a basis for future clinical trials to assess the indication and timing of splenectomy.     

Human papilloma virus specific T cells infiltrating cervical cancer and draining lymph nodes show remarkably frequent use of HLA-DQ and -DP as a restriction element

Human papillomavirus (HPV)-induced malignancies are frequently infiltrated by lymphocytes. To comprehend the contribution of HPV-specific T cells in this anti-tumor response we developed a method that allowed the analysis of the presence and specificity of cervix-infiltrating and draining lymph node resident T cells in a group of 74 patients with cervical malignancies, 54 of which were induced by HPV16 or HPV18. We detected the presence of HPV16 or HPV18-specific T cells in at least 23 of the 54 HPV-16 or -18 positive patients, and not in the 20 controls. Detailed studies resulted in the identification of 17 novel CD4+ and CD8+ T cell epitopes and their HLA-restriction elements, and also revealed that the HPV-specific immune response was aimed at both E6 and E7 and showed no preferential recognition of immunodominant regions. Unexpectedly, the vast majority of the CD4+ T cell epitopes were presented in the context of the less abundantly expressed HLA-DQ and HLA-DP molecules. Since the identified T cell epitopes constitute physiological targets in the immune response to HPV16 and HPV18 positive tumors they will be valuable for detailed studies on the interactions between the tumor and the immune system. This is crucial for the optimization of cancer immunotherapy in patients with pre-existing tumor-immunity.