Endotoxin-induced myeloid-derived suppressor cells inhibit alloimmune responses via heme oxygenase-1

Inflammation and cancer are associated with impairment of T-cell responses by a heterogeneous population of myeloid-derived suppressor cells (MDSCs) coexpressing CD11b and GR-1 antigens. MDSCs have been recently implicated in costimulation blockade-induced transplantation tolerance in rats, which was under the control of inducible NO synthase (iNOS). Herein, we describe CD11b+GR-1+MDSC-compatible cells appearing after repetitive injections of lipopolysaccharide (LPS) using a unique mechanism of suppression. These cells suppressed T-cell proliferation and Th1 and Th2 cytokine production in both mixed lymphocyte reaction and polyclonal stimulation assays. Transfer of CD11b+ cells from LPS-treated mice in untreated recipients significantly prolonged skin allograft survival. They produced large amounts of IL-10 and expressed heme oxygenase-1 (HO-1), a stress-responsive enzyme endowed with immunoregulatory and cytoprotective properties not previously associated with MDSC activity. HO-1 inhibition by the specific inhibitor, SnPP, completely abolished T-cell suppression and IL-10 production. In contrast, neither iNOS nor arginase 1 inhibition did affect suppression. Importantly, HO-1 inhibition before CD11b+ cell transfer prevented the delay of allograft rejection revealing a new MDSC-associated suppressor mechanism relevant for transplantation.

Translating transplantation tolerance in the clinic: where are we, where do we go?

Research networks dedicated to translation of immune tolerance in the clinic currently support pilot trials aiming at immunosuppression withdrawal in kidney or liver allograft recipients. Although results obtained so far indicate that significant hurdles still need to be overcome before organ transplant recipients can be weaned off drugs safely and routinely, recent advances suggest that immunosuppression minimization on the basis of validated biomarkers might become standard practice in a near future.

Interleukin-12 family members and type I interferons in Th17-mediated inflammatory disorders

Cytokines produced by antigen-presenting cells govern the fate of helper T-cell responses. Herein, we review the impact of interleukin (IL)-23 and IL-27 on the outcome of T-helper (Th) 17 cell responses and discuss their impact in the pathogenesis of T-cell-mediated inflammatory disorders of autoimmune or allergic origin. We then discuss how type I interferons might influence the course of autoimmune diseases by tipping the balance between IL-12 family members.

Quality aspects of the tissue microarray technique in a population-based cohort with ductal carcinoma in situ of the breast

AIMS

Tissue microarray (TMA) is an efficient technique for analysis of molecular markers. Prospectively collected samples have been reported to give excellent concordance between TMA data and corresponding whole-sections. The aim was to evaluate the usefulness of TMA in a population-based cohort of 213 women with ductal carcinoma in situ of the breast (DCIS).

METHODS AND RESULTS

We studied immunohistochemical HER2, oestrogen (ER) and progesterone (PR) receptor status. The prognostic impact was similar for all markers comparing whole sections and TMAs. The proportion of positive tumours was similar regarding HER2 and ER, whereas PR tumours were more frequently positive in the TMAs (P = 0.007). The concordance was 80% (kappa value 0.63) between original sections and TMAs. The proportion of successfully analysed tumours was 70%. Smaller tumours had a lower ratio (P < 0.0001) and a larger proportion of mismatched results (P = 0.05).

CONCLUSIONS

Retrospective analyses of tumours from cohorts with long-term follow-up are indispensable. We have shown that the TMA technique is a useful tool for high-throughput analysis of DCIS. However, our study has pinpointed some technical hazards within a population-based cohort, including many small lesions and the poor condition of some donor blocks. Mismatched results may be due to tumour heterogeneity.

[Involvement of natural regulatory lymphocytes in allograft tolerance]

Naturally occurring regulatory T-cells (Tregs) play a critical role in the homeostasis of healthy immune system. A Treg deficiency is responsible for immune system dysregulation, immune hyperreactivity and autoimmunity. Herein, we investigated the role of Tregs, either in the context of antibody-induced transplantation tolerance, mixed donor/recipient chimerism or in models of spontaneous graft acceptance without immunosuppression. We also investigated their capacities to control endotoxin-mediated immune response in the context of lymphopaenia-driven homeostatic T-cell proliferation. Finally, although Tregs adequately control Th1 and Th2 immunity, they are inefficient in regulating IL-17 producing T cells in vitro and in vivo and rather promote them.

CD8+ T-Cell depletion and rapamycin synergize with combined coreceptor/stimulation blockade to induce robust limb allograft tolerance in mice

The growing development of composite tissue allografts (CTA) highlights the need for tolerance induction protocols. Herein, we developed a mouse model of heterotopic limb allograft in a stringent strain combination in which potentially tolerogenic strategies were tested taking advantage of donor stem cells in the grafted limb. BALB/c allografts were transplanted into C57BL/6 mice treated with anti-CD154 mAb, nondepleting anti-CD4 combined to either depleting or nondepleting anti-CD8 mAbs. Some groups received additional rapamycin. Both depleting and nondepleting mAb combinations without rapamycin only delayed limb allograft rejection, whereas the addition of rapamycin induced long-term allograft survival in both combinations. Nevertheless, robust donor-specific tolerance, defined by the acceptance of a fresh donor-type skin allograft and simultaneous rejection of third-party grafts, required initial CD8(+) T-cell depletion. Mixed donor-recipient chimerism was observed in lymphoid organs and recipient bone marrow of tolerant but not rejecting animals. Tolerance specificity was confirmed by the inability to produce IL-2, IFN-gamma and TNF-alpha in MLC with donor antigen while significant alloreactivity persisted against third- party alloantigens. Collectively, these results show that robust CTA tolerance and mixed donor-recipient chimerism can be achieved in response to the synergizing combination of rapamycin, transient CD8(+) T-cell depletion and costimulation/coreceptor blockade.

The stethoscope as a vector of infectious diseases in the paediatric division

AIM

Nosocomial infections are of great concern in hospital settings, and even more so in the paediatric ward. Health professionals and their medical equipment have long been known to act as vectors of infectious diseases. This study aimed at evaluating the presence of bacterial pathogens on the stethoscopes of medical personnel in the paediatric division.

METHODS

Forty-three stethoscopes belonging to senior physicians, residents, interns and medical students at the paediatric ward were sampled. Bacterial cultures and antibiotic sensitivity testing were carried out.

RESULTS

All but six bacterial cultures were positive (85.7%). Staphylococcal species were the most common contaminants (47.5%). One case of methicillin-resistant Staphylococcus aureus was encountered. Gram-negative organisms were isolated in nine different samples (21%) including one case of Acinetobacter baumannii in the neonatal intensive care unit.

CONCLUSION

Most stethoscopes harbour potential pathogens. The isolation of Gram-negative organisms pose a real risk of spreading potentially serious infections, especially in the setting of intensive care departments. Apparently, the current recommendations of regular disinfection of stethoscopes are not carried out by health personnel that participated in the study.

Interleukin-22 deficiency accelerates the rejection of full major histocompatibility complex-disparate heart allografts

Interleukin-22 (IL-22) was recently described as an effector cytokine produced by TH17 CD4(+) T lymphocytes that, cooperatively with IL-17, mediates IL-23-driven inflammation. Because there was experimental evidence for the role of IL-17 in acute rejection of vascularized allografts, we undertook the present study to assess the function of IL-22 in the process. There was an early transient expression of IL-22 in C57BL/6 mouse cardiac allografts (2-4 days posttransplantation) transplanted to BALB/c recipients. The main source of IL-22 among infiltrating leukocytes was cells expressing the macrophage/monocyte markers Mac3 and CD11b. T cells and granulocytes present in the rejected graft did not express IL-22. Surprisingly, the absence of IL-22 accelerated the rejection of fully histoincompatible hearts. Histology of rejected organs revealed the presence of intensive intragraft thrombosis and disseminated hemorrhagic necrosis. Taken together, these results demonstrated that IL-22 was not an effector lymphokine in cardiac allograft rejection, but early intragraft expression of the cytokine protected it from rejection.

Modeling human respiratory impedance in Hispanic asthmatic children

Central (large airway) and peripheral (small airway) dysfunction frequently occur in patients with asthma and chronic obstructive lung disease. Measurement of the respiratory impedance can assist with diagnosis of pathological conditions. The forced Oscillation technique (FOT) superimposes small pressure perturbations at the mouth during tidal breathing of a subject to measure lung mechanical parameters. The Impulse Oscillometry System (IOS) is a commercial instrument that measures forced oscillatory impedance. IOS can be conveniently used in children as it only requires their passive cooperation during pulmonary function testing. Forced oscillatory impedance can be analyzed with respiratory system equivalent electrical circuit models. Models of varying complexity and fidelity have been developed to provide better understanding of respiratory mechanics and enable greater specificity of the diagnosis. Parameter estimates for these models can be used as reference values for detection and diagnosis of different respiratory pathologies. Previous work by our group has evaluated several known respiratory models and a new RIC model (augmented RIC) has emerged which offers advantages over earlier models. It has been shown that one parameter of this new model (representing peripheral airway compliance) is capable of discriminating between normal and asthmatic children. In this paper, we analyzed IOS data from 40 Hispanic asthmatic children and obtained sensitive impulse oscillometric parameters of lung function as well as parameter estimates for the augmented RIC (aRIC) model to distinguish between constricted (asthmatic condition) and non-constricted (non-asthmatic condition) airways with very promising results.

A study of IOS data using two mead-related models of respiratory impedance

This paper introduces two new respiratory system models, the Mead-Cw model and the Mead-Cl model, which are 6-component models that are intermediate in complexity between the well-known 7-component Mead model and the recently proposed 5-component augmented RIC model (derived from the Mead model by eliminating both Cw and Cl). Their modeling errors were compared to the RIC, extended RIC, augmented RIC and Mead models, for component values estimated from IOS data. The two new models yielded lower errors than all the other models, except for the Mead model. However, the Mead-Cl model and the Mead-Cw model also yielded unreasonably large values for Cw and Cl, respectively, which are known disadvantages of the Mead model. Hence the augmented RIC model appears to be the most useful at present for IOS-based computer-aided detection and diagnosis of respiratory disorders.

Can asthma in children be detected by the estimated parameter values of the augmented RIC model?

This paper describes the estimation of the parameter values for the recently introduced augmented RIC respiratory system model from impulse oscillometry data obtained from both asthmatic and normal children. An analysis of these values has indicated that one of the capacitance parameters of the model provides good discrimination between these two groups of children; moreover, this finding corresponds well with current medical understanding of the pathology of asthma.

[Transplantation tolerance: European Union meets the challenge]

Recent developments in basic and translational immunology open new exciting perspectives for the induction of transplantation tolerance in the clinic. However, a number of hurdles still need to be overcome before immunosuppressive drugs can be safely withdrawn in solid organ transplant recipients. With this background, the European Commission recently launched several initiatives to tackle unmet needs in transplantation medicine. Herein, we focus attention on the RISET project, an ongoing collaborative effort across the European Union aiming at minimization of immunosuppression on the basis of validated biomarkers.

Skin biopsies in DC vaccines for stage III-IV melanoma patients: role of neutrophils?

Dendritic cell (DC) vaccines are used for the induction of anti-tumor T cell reaction in melanoma patients. DC are generated in vitro, pulsed with antigen and matured prior to injection. They are supposed to migrate to lymph nodes and to present the processed antigen to naive T cells allowing activation of tumor-specific lymphocytes. It has been suggested that intradermal injection allows a superior migration to the lymph node. Eight HLA-A2 positive patients with stage III or IV melanomas expressing NA 17 antigen were collected. They were included in a pilot trial of vaccination in which they received IL3/INFb DC presenting the NA17 A2 antigen. In each patient, a skin biopsy was performed at the injection site, 24 h after inoculation. The striking features of the biopsies were the presence of a perivascular CD3+/CD8+ T cell infiltrate with a slight population of CD4+ cells and the presence of a massive neutrophilic infiltrate associated with the injected DC still present, realizing a suppurative granuloma. The persistence of DC 24 h after the injection suggests that migration in the lymph node is not necessary for the induction of the immune response. The skin itself could be the location of a reaction starting with a massive recruitment of neutrophils.