On the mechanical significance of vascular imprints of the human neurocranium when impacted at 11 m/s

The course of the middle meningeal vessels can be traced through imprints on the inner table of the human neurocranium. It is as yet unexplored whether these notches lower the load-bearing capacity of the bone when compared to areas that are free of vascular imprints. Here, 310 temporo-parietal samples with and without vascular imprints, from 52 human Crosado-embalmed cadavers, were tested in a three-point bending setup with a half-cylindrical impactor (1 mm radius of curvature) contacting the sample at 11 m/s. The maximum forces before breaking, and the thicknesses of the samples, were statistically compared, including comparing the avascular group to several groups with vascular imprints of different orientations. Furthermore, the influence of sample length and impact location were investigated. To investigate structure and mechanical function of vascular imprints concomitantly, scanning electron microscopy was performed on selected samples in two different planes. The results showed that avascular samples were on average thicker (p < 0.001) and stronger (p ≤ 0.050) compared to samples with vascular imprints. When only thickness-matched samples were analysed, the observed maximum forces of vascular and avascular samples were statistically similar (p ≥ 0.531). Regarding the load-bearing capacity of samples with vascular imprints, it was irrelevant whether the imprint was placed parallel to and directly underneath the impactor, parallel to and offset from the impactor, or perpendicular to the impactor (p > 0.999). The overall results of this study were statistically unrelated to both sample length (p ≥ 0.720) and impact location (p > 0.999). Scanning electron microscopy revealed that vascular imprints are formed through a curve of the inner table. Perforating holes of the inner table are present in avascular areas, however, they are considerably larger in size and higher in number within vascular imprints. In conclusion, vascular imprints are formed through curving of the inner table. In numerical models of human head mechanics, vascular imprints can be accounted for through a simple thinning of the bone assuming the same load-bearing capacity as for the surrounding imprint-free areas.

The Influence of Saliva and Blood Contamination on Bonding Between Resin-modified Glass Ionomer Cements and Resin Composite

OBJECTIVE

To investigate the influence of blood and saliva contamination on the microshear bond strength (μSBS) between resin-modified glass ionomer cement (RMGIC) and resin composite (RC).

METHODS AND MATERIALS

Eighty RMGIC discs were allocated into four groups (n=20). Group 1 received universal dental adhesive application in a self-etch mode followed by a build-up with RC. Group 2 received saliva as a contaminant, Group 3 received blood as a contaminant, Group 4 received a 1:1 blood-saliva mixture as a contaminant. Specimens from Groups 2, 3, and 4 were submerged into their respective contaminants for 15 seconds and dried prior to the adhesive application, followed by the protocol for Group 1. All specimens were stored in distilled water for 24 hours. Subsequently, the bonded specimens were subjected to μSBS testing using a universal testing machine. Failure mode of the debonded RMGIC surfaces was examined using scanning electron microscopy.

RESULTS

The μSBS from groups 1-4 were 10.76 ± 3.03 MPa, 9.36 ± 2.54 MPa, 6.55 ± 1.67 MPa and 8.42 ± 2.79 MPa, respectively. Contamination by blood and blood-saliva significantly decreased the μSBS (p<0.001, p=0.029). Saliva contamination alone had no statistically significant effect on the μSBS (p=0.524). A statistically significant difference in the mode of failure was detected between the experimental groups (p=0.012).

CONCLUSION

Saliva contamination has no influence on μSBS between RMGIC and RC when it is dried thoroughly, while blood and blood-saliva contamination reduced μSBS between RMGIC and RC even when dried thoroughly.

Dynamic load response of human dura mater at different velocities

Despite of its assumed role to mitigate brain tissue response under dynamic loading conditions, the human dura mater is frequently neglected in computational and physical human head models. A reason for this is the lack of load-deformation data when the dura mater is loaded dynamically. To date, the biomechanical characterization of the human dura mater predominantly involved quasi-static testing setups. This study aimed to investigate the strain rate-dependent mechanical properties of the human dura mater comparing three different velocities of 0.3, 0.5 and 0.7 m/s. Samples were chosen in a perpendicular orientation to the visible main fiber direction on the samples' surface, which was mostly neglected in previous studies. The elastic modulus of dura mater significantly increased at higher velocities (5.16 [3.38; 7.27] MPa at 0.3 m/s versus 44.38 [35.30; 74.94] MPa at 0.7 m/s). Both the stretch at yield point λ_f (1.148 [1.137; 1.188] for 0.3 m/s, 1.062 [1.054; 1.066] for 0.5 m/s and 1.015 [1.012; 1.021] for 0.7 m/s) and stress at yield point σ_f of dura mater (519.14 [366.74; 707.99] kPa for 0.3 m/s versus 300.52 [245.31; 354.89] kPa at 0.7 m/s) significantly decreased with increasing velocities. Conclusively, increasing the load application velocity increases stiffness and decreases tensile strength as well as straining potential of human dura mater between 0.3 and 0.7 m/s. The elastic modulus of human dura mater should be adapted to the respective velocities in computational head impact simulations.

On the correlations of biomechanical properties of super-imposed temporal tissue layers and their age-, sex-, side- and post-mortem interval dependence

Obtaining biomechanical properties of biological tissues for simulation purposes or graft developments is time and resource consuming. The number of samples required for biomechanical tests could be reduced if the load-deformation properties of a given tissue layer could be estimated from adjacent layers or if the biomechanical parameters were unaffected by age, bodyside, sex or post-mortem interval. This study investigates for the first time potential correlations of multiple super-imposed tissue layers using the temporal region of the human head as an area of broad interest in biomechanical modelling. Spearman correlations between biomechanical properties of the scalp, muscle fascia, muscle, bone and dura mater from up to 83 chemically unfixed cadavers were investigated. The association with age, sex and post-mortem interval was assessed. The results revealed sporadic correlations between the corresponding layers, such as the maximum force (r = 0.43) and ultimate tensile strength (r = 0.33) between scalp and muscle. Side- and age-dependence of the biomechanical properties were different between the tissue types. Strain at maximum force of fascia (r = -0.37) and elastic modulus of temporal muscle (r = 0.26) weakly correlated with post-mortem interval. Only strain at maximum force of scalp differed significantly between sexes. Uniaxial biomechanical properties of individual head tissue layers can thus not be estimated solely based on adjacent layers. Therefore, correlations between the tissues' biomechanical properties, anthropometric data and post-mortem interval need to be established independently for each layer. Sex seems not to be a relevant influencing factor for the passive tissue mechanics of the here investigated temporal head tissue layers.

Computed tomography osteoabsorptiometry-based investigation on subchondral bone plate alterations in sacroiliac joint dysfunction

Sacroiliac joint dysfunction (SIJD) is an underappreciated source of back pain. Mineralization patterns of the sacroiliac (SIJ) subchondral bone plate (SCB) may reflect long-term adaptations to the loading of the joint. Mineralization densitograms of 27 SIJD patients and 39 controls, were obtained using CT osteoabsorptiometry. Hounsfield unit (HU) values of the SCB mineralization of superior, anterior and inferior regions on the iliac and sacral auricular surfaces were derived and statistically compared between SIJD-affected and control cohorts. Healthy controls showed higher HU values in the iliac; 868 ± 211 (superior), 825 ± 121 (anterior), 509 ± 114 (inferior), than in the sacral side; 541 ± 136 (superior), 618 ± 159 (anterior), 447 ± 91 (inferior), of all regions (p < 0.01). This was similar in SIJD; ilium 908 ± 170 (superior), 799 ± 166 (anterior), 560 ± 135 (inferior), sacrum 518 ± 150 (superior), 667 ± 151 (anterior), 524 ± 94 (inferior). In SIJD, no significant HU differences were found when comparing inferior sacral and iliac regions. Furthermore, HU values in the inferior sacral region were significantly higher when compared to the same region of the healthy controls (524 ± 94 vs. 447 ± 91, p < 0.01). Region mineralization correlated negatively with age (p < 0.01). SIJD-affected joints reflect a high mineralization of the sacral inferior region, suggesting increased SIJD-related mechanical stresses. Age-related SCB demineralization is present in all individuals, regardless of dysfunction.

On the morphological relations of the Achilles tendon and plantar fascia via the calcaneus: a cadaveric study

Current treatments of plantar fasciitis are based on the premise that the Achilles tendon (AT) and plantar fascia (PF) are mechanically directly linked, which is an area of debate. The aim of this study was to assess the morphological relationship between the AT and PF. Nineteen cadaveric feet were x-ray imaged, serially sectioned and plastinated for digital image analyses. Measurements of the AT and PF thicknesses and cross-sectional areas (CSA) were performed at their calcaneal insertion. The fiber continuity was histologically assessed in representative subsamples. Strong correlations exist between the CSA of the AT and PF at calcaneal insertion and the CSA of PF's insertional length (r = 0.80), and between the CSAs of AT's and PF's insertional lengths. Further correlations were observed between AT and PF thicknesses (r = 0.62). This close morphological relationship could, however, not be confirmed through x-ray nor complete fiber continuity in histology. This study provides evidence for a morphometric relationship between the AT and PF, which suggests the presence of a functional relationship between these two structures following the biological key idea that the structure determines the function. The observed morphological correlations substantiate the existing mechanical link between the AT and PF via the posterior calcaneus and might explain why calf stretches are a successful treatment option for plantar heel pain.

Assessment of plantaris and peroneus tertius tendons as graft materials for ankle ligament reconstructions - A cadaveric biomechanical study

Both the plantaris tendon and the peroneus tertius tendon are used as auto- and allogenous graft materials to reconstruct the ankle ligament complex. However, it is unclear to what extent these graft materials resemble the load-deformation behavior of the ankle ligaments. A total of 34 human ankle ligaments and 35 tendons were assessed mechanically deploying a quasi-static tensile testing setup. Tendons were significantly stiffer (median elastic moduli: plantaris tendon = 465.7 MPa, peroneus tertius tendon = 338.5 MPa, medial ligament = 61.4 MPa, lateral ligament = 49.3 MPa; p ≤ 0.035), but more distensible (median strain at maximum force: plantaris tendon = 15.1%, peroneus tertius tendon = 15.3%, medial ligament = 9.3%, lateral ligament = 9.6%; p ≤ 0.008) and mechanically tougher (median ultimate tensile strength: plantaris tendon = 51.0 MPa, peroneus tertius tendon = 40.5 MPa, medial ligament = 4.1 MPa, lateral ligament = 3.5 MPa; p ≤ 0.033) when compared to medial and lateral ankle ligaments. The lateral ligaments of the right ankle were significantly tougher compared to the left side (p = 0.015). The elastic modulus of the medial ligament (r = 0.489, p = 0.045) and the peroneus tertius tendon (r = 0.517, p = 0.014) yielded an age-dependent increase. Both tendons seem biomechanically suitable graft materials to replace the medial and lateral ankle ligaments during physiological loading. The age-dependent increase in tissue elastic properties of the medial vs. lateral ankle ligaments, and differences in ultimate tensile strength between the lateral ligaments left vs. right, may reflect the complex asymmetric loading behavior of both ankle ligaments.

Morphometric and density comparisons of Bos taurus scapulae as a proxy to human frontal crania

Background

In the absence of cadaveric tissues, forensic simulation, trauma modelling, and cranial surgical training necessitates a surrogate for the human calvaria. This study investigates the validity of Bos taurus scapulae as a proxy for human frontal bones by comparing the laminar and cancellous bone thickness, as well as the bone mineral density (BMD) of cadaveric frontal bones and adult Bos taurus scapulae.

Results

This study aimed to validate the bovine scapulae as a valid proxy for forensic experiments, which benefit researchers and investigators who need to recreate forensic scenarios where synthetic proxies are found unsuitable due to their non-viscoelastic nature and cadaveric human models are unavailable due to ethical restrictions. Our results identified different total thicknesses of the relative bones, but non-different cortical measurements between human frontal bone and bovine scapulae. The bone mineral density is similar between both groups.

Conclusion

This study has found Bos taurus scapulae to be a suitable proxy for human frontal bones as it has a similar morphology with regard to thickness and structure as well as a comparable density. However, there is a significant difference between the cancellous bone, and therefore, the overall thickness.

Suicide by the intraoral blast of firecrackers - experimental simulation using a skull simulant model

Suicides committed by intraorally placed firecrackers are rare events. Given to the use of more powerful components such as flash powder recently, some firecrackers may cause massive life-threatening injuries in case of such misuse. Innocuous black powder firecrackers are subject to national explosives legislation and only have the potential to cause harmless injuries restricted to the soft tissue. We here report two cases of suicide committed by an intraoral placement of firecrackers, resulting in similar patterns of skull injury. As it was first unknown whether black powder firecrackers can potentially cause serious skull injury, we compared the potential of destruction using black powder and flash powder firecrackers in a standardized skull simulant model (Synbone, Malans, Switzerland). This was the first experiment to date simulating the impacts resulting from an intraoral burst in a skull simulant model. The intraoral burst of a "D-Böller" (an example of one of the most powerful black powder firecrackers in Germany) did not lead to any injuries of the osseous skull. In contrast, the "La Bomba" (an example of the weakest known flash powder firecrackers) caused complex fractures of both the viscero- and neurocranium. The results obtained from this experimental study indicate that black powder firecrackers are less likely to cause severe injuries as a consequence of intraoral explosions, whereas flash powder-based crackers may lead to massive life-threatening craniofacial destructions and potentially death.

Pulmonary artery perforation and coronary air embolism-two fatal outcomes in percutaneous left atrial appendage occlusion

Percutaneous left atrial appendage (LAA) closure is a routinely performed method to reduce the risk of stroke in patients suffering from atrial fibrillation, when an oral anticoagulation is no longer indicated due to relevant bleeding complications. Currently, the Amplatzer Amulet and the Watchman system are two equally used systems. While there is an acute success rate of more than 95 per cent for this intervention, several minor and major complications such as pericardial effusions, air embolism, vascular lesions in proximity to the heart or even death can occur. Here, we report two cases of very rare fatal outcomes in percutaneous LAA occlusion. Eight hours after deployment of an Amplatzer Amulet a patient died, after the pulmonary trunk was perforated by a hook of the occluder device causing pericardial tamponade. In the second case during final radiological position control of the deployed Watchman occluder air was injected accidentally. The patient immediately died due to coronary air embolism. Forensic autopsies are necessary to solve the cause and manner of death, to evaluate and develop medical devices and to rule out medical malpractice. Thus, a close collaboration of legal medicine and the various cardiologic departments is proposed.

Circulating microparticles in patients with benign and malignant ovarian tumors

BACKGROUND

Microparticles are known to be increased in various malignancies. In this prospective study, microparticle levels were evaluated in patients with benign and malignant ovarian lesions.

PATIENTS AND METHODS

Microparticles from platelets/megakaryocytes, activated platelets and endothelial cells, tissue factor exposing microparticles and D-dimer values were examined in patients with newly diagnosed ovarian lesions before surgery, and were correlated with tumor histology.

RESULTS

Higher counts of CD63-positive microparticles were detected in patients with ovarian cancer [mean=276×10(6) (range: 64-948)/l; n=12] as compared to patients with benign ovarian tumors [146×10(6) (45-390)/l; n=21; p=0.014]. D-dimer values were also increased in patients with cancer [860 (180-4500) ng/l versus 280 (170-2720) ng/l; p=0.001].

CONCLUSION

Elevated levels of CD63-positive microparticles and D-dimer reflect the procoagulant phenotype of these patients. However, for the discrimination between benign and malignant ovarian tumors, measuring preoperative levels of microparticles does not seem to be helpful.

Mast cell activation is characterized by upregulation of a functional anaphylatoxin C5a receptor

BACKGROUND

Mast cells (MC) are key effector cells of allergic diseases and resistance to helminthic parasites and induce or amplify diverse innate and adaptive immune responses. The signals controlling MC mobilization during inflammation are not fully understood.

RESULTS

Since anaphylatoxins are attractive candidates as MC chemoattractants, we investigated expression and function of anaphylatoxin receptors in murine MC. Precursor cell-derived MC cultured with IL-3 in the presence or absence of SCF did not express significant amounts of surface C5a receptor (C5aR) or C3a receptor (C3aR). MC required approximately 4 h of stimulation with Ag (DNP-albumin, following preincubation with IgE anti-DNP), ionomycin, or PMA to enable a strong chemotactic response towards C5a, paralleled by a distinct C5aR upregulation. Likewise, C5a induced intracellular calcium fluxes solely in activated MC. In contrast, C3a proved to be a weak MC chemotaxin and unable to increase intracellular calcium. Primary peritoneal MC did not express detectable amounts of anaphylatoxin receptors, however, similar to precursor cell-derived MC, stimulation with Ag or ionomycin for 4 h induced a prominent surface expression of C5aR whereas C3aR remained undetectable.

CONCLUSION

Collectively, our results suggest that Ag-dependent as well as -independent activation induces an inflammatory MC phenotype which is distinguished by neoexpression of a functional C5aR as a novel effector mechanism in MC-mediated pathogenesis.

Chemoattraction of macrophages, T lymphocytes, and mast cells is evolutionarily conserved within the human alpha-defensin family

Human defensins are natural peptide antibiotics. On the basis of the position and bonding of six conserved cysteine residues, they are divided into two families, designated alpha- and beta-defensins. Human alpha-defensins are expressed predominantly in neutrophils (human neutrophil peptides (HNP) 1-4) or intestinal Paneth cells (human defensins (HD) 5 and 6). Although alpha-defensins have been implicated in the pathogenesis of inflammatory bowel disease, their immunomodulatory functions are poorly understood. In the present study, HNP-1, HNP-3, and HD5 were found to be potent chemotaxins for macrophages but not dendritic cells using Galphai proteins and MAPK as signal transducers. Alpha-defensins were also chemoattractive for the human mast cell line HMC-1 but lacked, in contrast to beta-defensins, the ability to induce intracellular calcium fluxes. Furthermore, HNP-1, HNP-3, and HD5 comparably mobilized naive as well as memory T lymphocytes. Using the protein kinase C (PKC) inhibitors GF109 and Gö6976, we observed a PKC-independent functional desensitization to occur between human alpha-defensins, which suggests a common receptor for HNP-1, HNP-3, and HD5 on immune cells. This alpha-defensin receptor was subject to heterologous desensitization by the PKC activator PMA and to PKC-dependent cross-desensitization by human beta-defensins. Conversely, alpha-defensins desensitized beta-defensin-mediated migration of immune cells in a PKC-dependent manner, suggesting unique receptors for both defensin families. Taken together, our observations indicate that chemoattraction of macrophages, T lymphocytes, and mast cells represents an immunomodulatory function which is evolutionarily conserved within the human alpha-defensin family and tightly regulated by beta-defensins.

beta-Defensins chemoattract macrophages and mast cells but not lymphocytes and dendritic cells: CCR6 is not involved

beta-Defensins are natural peptide antibiotics whose immunomodulatory functions are poorly understood. In the present study, macrophages were found to migrate to human beta-defensins (HBD)-1 to -4 using Galpha(i) proteins as well as MAPK ERK, p38 and JNK as signal transducers. In addition, mast cells responded to HBD-1 to -4 with calcium fluxes as well as chemotaxis, which increased upon stimulation with IgE plus antigen or ionomycin. In contrast, human beta-defensins were unable to induce migration of memory lymphocytes and dendritic cells (DC). Similar to HBD, the murine beta-defensin (mBD)-8 mobilized macrophages and lacked the ability to recruit memory T cells. These findings were unexpected as CCR6 on memory T cells and DC has been previously observed to be a receptor for human beta-defensins. In support of our findings, however, RBL-2H3 as well as 300.19 cells stably expressing CCR6 proved to be unresponsive to HBD-2 and -3. Intriguingly, our observation of a PKC-independent homologous desensitization between HBD-1 to -4 suggests a common receptor for HBD. In summary, chemoattraction of macrophages and mast cells is evolutionary conserved within the beta-defensin family despite a considerable sequence variation and distinct antimicrobial activities. However, CCR6 is not a functional receptor for beta-defensins.

Abrogation of CCL21 chemokine function by transgenic over-expression impairs T cell immunity to local infections

The CC chemokine receptor 7 (CCR7) and its two ligands, CCL21 and CCL19, play an important role in migration of immune cells to lymphoid tissue. To analyze the function of CCR7 in T cell immunity to infectious agents in vivo, transgenic (tg) mice expressing CCL21 in an ubiquitous fashion were generated. These mice contained high amounts of CCL21 in the serum ( approximately 0.3 microg/ml that resulted in CCR7 down-regulation and in a strongly impaired migration of T cells toward CCL21 in vitro. Lymph nodes in CCL21-tg mice were reduced in size but with intact microanatomy and normal distribution of T and B cells. CCL21-tg mice showed a significantly decreased CD8 T cell response to lymphocytic choriomeningitis virus after footpad infection, whereas the response after systemic infection was not altered. Likewise, the CD4 T cell response to footpad infection with Leishmania major was considerably lowered and CCL21-tg mice failed to clear parasites from infected skin. Taken together, these data demonstrate the importance of CCR7 in mediating T cell immunity to viral and parasitic pathogens after local infection.

TNF controls the infiltration of dendritic cells into the site of Leishmania major infection

TNF-negative C57BL/6 (B6.TNF(-/-)) mice are highly susceptible to Leishmania (L.) major infection and succumb rapidly to fatal leishmaniasis. A T helper type 1 (Th1) cell-mediated immune response is central for protective anti-leishmanial immunity. Therefore, the observed susceptibility of B6.TNF(-/-) mice to L. major parasites could be caused by a deficiency in mounting a Th1 response. Analysis of infected footpads revealed, that B6.TNF(-/-) mice exhibited a substantially diminished formation of DCs at the site of infection. Furthermore, Th1 cytokines such as IFN-gamma were reduced in footpads of infected B6.TNF(-/-) mice. Cutaneous reconstitution of B6.TNF(-/-) mice with either bone marrow derived DCs (BM-DCs) or recombinant TNF simultaneous to infection resulted in an increased expression of cytokines such as IFN-gamma and in an enhanced presence of Leishmania-antigen in skin draining lymph nodes. In addition, the individual time of survival was doubled. In conclusion we demonstrate that the expression of dermal TNF is necessary to provide an environment that initiates a local inflammatory response, but is not sufficient to induce protective immunity.

Use of monoclonal antibodies to assess expression of anaphylatoxin receptors in rat and murine models of lung inflammation

The anaphylatoxins C3a and C5a are involved in the pathophysiology of microbial as well as allergic inflammation in the lungs. Besides their expression in leukocytes, receptors for C3a and C5a (C3aR and C5aR) have been noted in alveolar and bronchial epithelial cells, bronchial smooth muscle cells as well as in vascular endothelial and smooth muscle cells of normal and inflamed human and murine lungs. Recently, however, expression of anaphylatoxin receptors in parenchymal cells of the lung (and kidney) has been challenged. Using well-characterized monoclonal antibodies (mabs) against murine and rat anaphylatoxin receptors, we reexamined the pulmonary distribution of C3aR and C5aR. Immunohistochemistry was performed on frozen sections of lung tissues from normal mice and rats as well as from animals subjected to lipopolysaccharide (LPS)-induced inflammation or from MRL/lpr mice suffering from autoimmune disease. Furthermore, ovalbumin (OVA)-induced models of allergic asthma in the rat and mouse were investigated. Prominent expression of both anaphylatoxin receptors was detectable in resident as well as infiltrating leukocytes. No C3aR protein was observed in alveolar macrophages. Upon LPS- and OVA-challenge as well as in autoimmune inflammation, numbers of infiltrating leukocytes expressing prominent amounts of anaphylatoxin receptors increased. Even under these highly inflammatory conditions, however, expression of C3aR and C5aR was not inducible in parenchymal cells. Thus, our findings identify infiltrating leukocytes as a prominent source of anaphylatoxin receptors in inflamed lungs. A direct involvement of parenchymal cells in anaphylatoxin-mediated pulmonary inflammation is unlikely.

Use of monoclonal antibodies to assess expression of anaphylatoxin receptors in tubular epithelial cells of human, murine and rat kidneys

To assess published evidence of anaphylatoxin receptor expression in renal tubular epithelial cells, monoclonal antibodies (mAbs) against human, mouse and rat receptors for C5a and C3a (C5aR, C3aR) were raised using receptor-expressing transfectants as immunogens. Applying these reagents in immunohistochemistry, we observed that mAbs with reactivities against three distinct epitopes of human C5aR N-terminus recognized tissue macrophages but not at all renal tubular epithelial cells. These findings were surprising, as strong tubular staining had been previously demonstrated by mAbs raised against a synthetic N-terminal C5aR peptide. To extend our study to mammalian kidneys, renal specimens from normal rats as well as LPS-treated Balb/c and MRL/lpr mice, which suffered from lupus-type nephritis, were examined. Similar to humans, mAbs against murine or rat C5aR strongly recognized infiltrating leukocytes in situ whereas tubular epithelial cells remained negative. As a mAb has been previously used to document C3aR expression in renal tubular epithelial cells, kidney specimens were examined using newly established mAbs against different epitopes of human, murine and rat C3aR. In contrast to published evidence, C3aR was detectable exclusively in interstitial leukocytes but not in epithelial tubular cells of normal and diseased tissues. Taken together, our findings question a direct involvement of tubular epithelial cells in anaphylatoxin-mediated renal inflammation. Furthermore, as we demonstrate in the case of anaphylatoxin receptors, cross-reactivities of mAbs may constitute as yet underestimated pitfalls in immunohistochemical antigen detection.

Induction of C3 and CCL2 by C3a in keratinocytes: a novel autocrine amplification loop of inflammatory skin reactions

The complement fragment-3a (C3a) acts via a G protein-coupled C3aR and is of importance in allergic and inflammatory diseases. Recent studies suggest the presence of complement proteins in the epidermal compartment and synthesis of some of these proteins (C3, factor B, and factor H) by human primary keratinocytes (KCs) during inflammation. However, expression of C3aR and its role in human KCs is not elucidated thus far. In this study, we demonstrate the expression of C3aR on KCs as detected by quantitative real-time RT-PCR and flow cytometry. IFN-gamma and IFN-alpha strongly up-regulated the surface expression of C3aR on KCs among all other cytokines tested. After up-regulation of C3aR by IFN-gamma and IFN-alpha, we observed the induction of five genes (CCL2, CCL5, CXCL8, CXCL10, and C3) after stimulation of KCs with C3a in microarray analysis. We confirmed the induction of C3 and CCL2 at RNA and protein levels. Furthermore, incubation of C3 with skin mast cells tryptase resulted in the generation of C3 fragments with C3a activity. In conclusion, our data illustrate that epidermal KCs express functional C3aR. The increases of C3 and CCL2 synthesis by C3a and C3 activation by skin mast cell tryptase delineates a novel amplification loop of complement activation and inflammatory responses that may influence the pathogenesis of allergic/inflammatory skin diseases.

Human C5aR knock-in mice facilitate the production and assessment of anti-inflammatory monoclonal antibodies

Complement component C5a binds C5a receptor (C5aR) and facilitates leukocyte chemotaxis and release of inflammatory mediators. We used neutrophils from human C5aR knock-in mice, in which the mouse C5aR coding region was replaced with that of human C5aR, to immunize wild-type mice and to generate high-affinity antagonist monoclonal antibodies (mAbs) to human C5aR. These mAbs blocked neutrophil migration to C5a in vitro and, at low doses, both prevented and reversed inflammatory arthritis in the murine K/BxN model. Of approximately 40 mAbs generated to C5aR, all potent inhibitors recognized a small region of the second extracellular loop that seems to be critical for regulation of receptor activity. Human C5aR knock-in mice not only facilitated production of high-affinity mAbs against an important human therapeutic target but were also useful in preclinical validation of the potency of these antagonists. This strategy should be applicable to other important mAb therapeutics.

Functional specialization of memory Th cells revealed by expression of integrin CD49b

Infection or immunization induces heterogeneous memory T cell subsets, but their origin and protective value against infection are unclear. In this study, we report the functional characterization of two memory Th subsets, defined by expression of integrin CD49b. Stable CD49b expression is induced in up to one-half of all memory Th cells. More importantly, the CD49b- and CD49b+ subsets display distinct helper activities, typified by the production of IL-10 and TNF-alpha, respectively. Although the inflammatory properties of the CD49b+ subset are protective against intracellular bacterial infection, they are associated with immunopathology in acute viral infection. Modulation of the CD49b-defined memory Th subsets may provide infection type-specific interventions, where either enhancement of the inflammatory response or reduction of immunopathology is essential.

Human plasmacytoid dendritic cells express receptors for anaphylatoxins C3a and C5a and are chemoattracted to C3a and C5a

The presence of plasmacytoid dendritic cells (pDC) was recently demonstrated in lesions of inflammatory skin diseases. Since anaphylatoxins or their precursors were also found in such lesions, we investigated a possible interaction between pDC and anaphylatoxins C3a and C5a. pDC precursors isolated from peripheral blood did not express the receptors for C3a and C5a, complement C3a receptor (C3aR) and complement C3a receptor (C5aR). If these pDC precursors were cultured with IL-3, the resultant immature pDC expressed both receptors. Expression of C3aR and C5aR could also be demonstrated on pDC in lesions of cutaneous lupus erythematosus and allergic contact dermatitis. Such pDC were immature since they lacked the expression of the maturation marker CD83. Blood-derived pDC matured with CpG oligonucleotides downregulated the receptors. Immature pDC responded to C3a and C5a (but not C3adesArg) stimulation with increased F-actin polymerization and chemotactic migration. In contrast, interferon alpha production, surface molecule expression, and T-cell stimulatory capacity were not significantly modulated by C3a or C5a. Thus, immature pDC represent another type of antigen-presenting cell that express C3aR and C5aR, and respond to anaphylatoxins with chemotaxis. This might be relevant in the direction of pDC to cutaneous lesions of inflammation, for example, in lupus erythematosus or contact dermatitis.

A regulatory role for the C5a anaphylatoxin in type 2 immunity in asthma

Complement component 5 (C5) has been described as either promoting or protecting against airway hyperresponsiveness (AHR) in experimental allergic asthma, suggesting pleomorphic effects of C5. Here we report that local pharmacological targeting of the C5a receptor (C5aR) prior to initial allergen sensitization in murine models of inhalation tolerance or allergic asthma resulted in either induction or marked enhancement of Th2-polarized immune responses, airway inflammation, and AHR. Importantly, C5aR-deficient mice exhibited a similar, increased allergic phenotype. Pulmonary allergen exposure in C5aR-targeted mice resulted in increased sensitization and accumulation of CD4+ CD69+ T cells associated with a marked increase in pulmonary myeloid, but not plasmacytoid, DC numbers. Pulmonary DCs from C5aR-targeted mice produced large amounts of CC chemokine ligand 17 (CCL17) and CCL22 ex vivo, suggesting a negative impact of C5aR signaling on pulmonary homing of Th2 cells. In contrast, C5aR targeting in sensitized mice led to suppressed airway inflammation and AHR but was still associated with enhanced production of Th2 effector cytokines. These data suggest a dual role for C5a in allergic asthma, i.e., protection from the development of maladaptive type 2 immune responses during allergen sensitization at the DC/T cell interface but enhancement of airway inflammation and AHR in an established inflammatory environment.

Cell-derived anaphylatoxins as key mediators of antibody-dependent type II autoimmunity in mice

Complement C5a, a potent anaphylatoxin, is a candidate target molecule for the treatment of inflammatory diseases, such as myocardial ischemia/reperfusion injury, RA, and the antiphospholipid syndrome. In contrast, up until now, no specific contribution of C5a and its receptor, C5aR, was recognized in diseases of antibody-dependent type II autoimmunity. Here we identify C5a as a novel key mediator of autoimmune hemolytic anemia (AIHA) and show that mice lacking C5aR are partially resistant to this IgG autoantibody-induced disease model. Upon administration of anti-erythrocyte antibodies, upregulation of activating Fcgamma receptors (FcgammaRs) on Kupffer cells, as observed in WT mice, was absent in C5aR-deficient mice, and FcgammaR-mediated in vivo erythrophagocytosis was impaired. Surprisingly, in mice deficient in FcgammaRI and FcgammaRIII, anti-erythrocyte antibody-induced C5 and C5a production was abolished, demonstrating the existence of a previously unidentified FcgammaR-mediated C5a-generating pathway. These results show that the development of a full-blown antibody-dependent autoimmune disease requires C5a--produced by and acting on FcgammaR--and may suggest therapeutic benefits of C5 and/or C5a/C5aR blockade in AIHA and other diseases closely related to type II autoimmune injury.

Complement: a novel factor in basal and ischemia-induced neurogenesis

Through its involvement in inflammation, opsonization, and cytolysis, the complement protects against infectious agents. Although most of the complement proteins are synthesized in the central nervous system (CNS), the role of the complement system in the normal or ischemic CNS remains unclear. Here we demonstrate for the first time that neural progenitor cells and immature neurons express receptors for complement fragments C3a and C5a (C3a receptor (C3aR) and C5a receptor). Mice that are deficient in complement factor C3 (C3(-/-)) lack C3a and are unable to generate C5a through proteolytic cleavage of C5 by C5-convertase. Intriguingly, basal neurogenesis is decreased both in C3(-/-) mice and in mice lacking C3aR or mice treated with a C3aR antagonist. The C3(-/-) mice had impaired ischemia-induced neurogenesis both in the subventricular zone, the main source of neural progenitor cells in adult brain, and in the ischemic region, despite normal proliferative response and larger infarct volumes. Thus, in the adult mammalian CNS, complement activation products promote both basal and ischemia-induced neurogenesis.

S19 ribosomal protein dimer augments metal-induced apoptosis in a mouse fibroblastic cell line by ligation of the C5a receptor

To analyze the role of S19 ribosomal protein (RP S19) in apoptosis, murine NIH3T3 were transfected with either hemagglutinin peptide-tagged (HA) wild-type human RP S19 or a mutant (Gln137Asn) that is resistant to transglutaminase-catalyzed cross-linked-dimerization. Transfection with the mutant HA-RP S19 inhibited manganese (II) (Mn II)-induced apoptosis whereas the wild-type HA-RP S19 augmented apoptosis and a mock transfection had no effect. Release of the wild-type HA-RP S19 dimer but not the mutant HA-RP S19 was observed during the apoptosis. The reduced rate of apoptosis of the cells transfected with the mutant HA-RP S19 was overcome by addition of extracellular wild-type RP S19 dimer. The apoptosis rates in cells transfected with either form of human HA-RP S19 and in mock transfectants were reduced to about 40% by the presence of anti-RP S19 antibody in the culture medium. Immunofluorescence staining and fluorescence-activated cell sorting (FACS) analysis showed that the cell surface expression of the receptor for cross-linked RP S19 dimer, C5a receptor, increased during apoptosis, concomitant with phosphatidylserine exposure. The expression of the C5a receptor gene also increased twofold. Apoptosis rates in the transfected and control cell lines were also reduced by the presence of an anti-mouse C5a receptor monoclonal antibody or of a peptide C5a receptor antagonist. These results indicated the presence of an RP S19 dimer- and C5a receptor-mediated autocrine-type augmentation mechanism during Mn II-induced apoptosis in the mouse fibroblastic cell line. In contrast to the RP S19 dimer, C5a actually inhibited apoptosis, suggesting that signaling through the C5a receptor varies depending on the ligand bound.

Macrophages induce the inflammatory response in the pulmonary Arthus reaction through G alpha i2 activation that controls C5aR and Fc receptor cooperation

Complement and FcgammaR effector pathways are central triggers of immune inflammation; however, the exact mechanisms for their cooperation with effector cells and their nature remain elusive. In this study we show that in the lung Arthus reaction, the initial contact between immune complexes and alveolar macrophages (AM) results in plasma complement-independent C5a production that causes decreased levels of inhibitory FcgammaRIIB, increased levels of activating FcgammaRIII, and highly induced FcgammaR-mediated TNF-alpha and CXCR2 ligand production. Blockade of C5aR completely reversed such changes. Strikingly, studies of pertussis toxin inhibition show the essential role of G(i)-type G protein signaling in C5aR-mediated control of the regulatory FcgammaR system in vitro, and analysis of the various C5aR-, FcgammaR-, and G(i)-deficient mice verifies the importance of Galpha(i2)-associated C5aR and the FcgammaRIII-FcgammaRIIB receptor pair in lung inflammation in vivo. Moreover, adoptive transfer experiments of C5aR- and FcgammaRIII-positive cells into C5aR- and FcgammaRIII-deficient mice establish AM as responsible effector cells. AM lacking either C5aR or FcgammaRIII do not possess any such inducibility of immune complex disease, whereas reconstitution with FcgammaRIIB-negative AM results in an enhanced pathology. These data suggest that AM function as a cellular link of C5a production and C5aR activation that uses a Galpha(i2)-dependent signal for modulating the two opposing FcgammaR, FcgammaRIIB and FcgammaRIII, in the initiation of the inflammatory cascade in the lung Arthus reaction.

Dendritic cells: limited potential in immunotherapy

Dendritic cells (DC) represent the most potent antigen-presenting cells (APC) of the immune system for their unique capability of presenting antigen to T-cells. Their use as cellular vaccines after charging with antigen ex vivo has been shown to induce protective and therapeutic anti-tumor immunity with regression of tumor manifestations in animal models of experimental cancer therapy. Human monocyte-derived DC (MoDC) generated in vitro in the presence of GM-CSF and IL-4 are regarded equivalent to immature DC. They can be induced to mature under various experimental conditions. MoDC, in their immature as well as mature state have been widely used for experimental as well as for clinical purposes. However, unequivocal proof for the clinical efficiency of MoDC-based anti-tumor vaccinations is still missing. There is now increasing experimental evidence demonstrating that MoDC may be hampered in their ability to migrate in response to inflammatory as well as homeostatic chemataxins. We therefore suggest that MoDC may not represent the equivalent of migratory DC in vivo limiting their use as magic bullets in tumor immunotherapy.

Impaired dendritic-cell homing in vivo in the absence of Wiskott-Aldrich syndrome protein

Regulated migration and spatial localization of dendritic cells (DCs) are critical events during the initiation of physiologic immune responses and maintenance of tolerance. Here we have used cells deficient in the Wiskott-Aldrich syndrome protein (WASp) to demonstrate the importance of dynamic remodeling of the actin cytoskeleton for these trafficking processes to occur in vitro and in vivo. On fibronectin-coated surfaces, WASp-null immature murine DCs exhibited defects both of attachment and detachment, resulting in impaired net translocation compared with normal cells. The chemokinetic response to CCL21, which is critical for normal lymphatic trafficking, was also abrogated in the absence of WASp. In vivo in both fluorescein isothiocyanate (FITC) and oxazolone contact hypersensitivity models, WASp-null Langerhans cell (LC) migration was compromised, as judged by exit from the skin as well as by homing to the draining lymph node (LN). Furthermore, following systemic challenge with lipopolysaccharide (LPS) or toxoplasma-derived antigen, WASp-null DCs showed incomplete redistribution to T-cell areas in the spleen. Instead, they were retained ectopically in the marginal zone. DC trafficking in vivo is therefore dependent on a normally regulated actin cytoskeleton, which performs an essential function during maintenance of physiologic immunity and when disturbed may contribute significantly to the immunopathology of Wiskott-Aldrich Syndrome.

C5a initiates the inflammatory cascade in immune complex peritonitis

Immune complex (IC)-induced inflammation is integral to the pathogenesis of several autoimmune diseases. ICs activate the complement system and interact with IgG FcgammaR. In this study, we demonstrate that activation of the complement system, specifically generation of C5a, initiates the neutrophilic inflammation in IC peritonitis. We show that ablation of C5a receptor signaling abrogates neutrophil recruitment in wild-type mice and prevents the enhancement of neutrophil migration seen in FcgammaRIIB(-/-) mice, suggesting that C5aR signaling is the crucial initial event upstream of FcgammaR signaling. We also provide evidence that C5a initiates the inflammatory cascade both directly, through C5aR-mediated effector functions on infiltrating and resident peritoneal cells, and indirectly, through shifting the balance between activating and inhibitory FcgammaRs on resident cells toward an inflammatory phenotype. We conclude that complement activation and C5a generation are prerequisites for IC-induced inflammation through activating FcgammaR, which amplifies complement-induced inflammation in autoimmunity.

CCR7 governs skin dendritic cell migration under inflammatory and steady-state conditions

The CC chemokine receptor CCR7 has been identified as a key regulator of homeostatic B and T cell trafficking to secondary lymphoid organs. Data presented here demonstrate that CCR7 is also an essential mediator for entry of both dermal and epidermal dendritic cells (DC) into the lymphatic vessels within the dermis while this receptor is dispensable for the mobilization of Langerhans cells from the epidermis to the dermis. Moreover, a distinct population of CD11c(+)MHCII(high) DC showing low expression of the costimulatory molecules CD40, CD80, and CD86 in wild-type animals was virtually absent in skin-draining lymph nodes of CCR7-deficient mice under steady-state conditions. We provide evidence that these cells represent a semimature population of DC that is capable of initiating T cell proliferation under conditions known to induce tolerance. Thus, our data identify CCR7 as a key regulator that governs trafficking of skin DC under both inflammatory and steady-state conditions.

Analysis of the CCR7 expression on murine bone marrow-derived and spleen dendritic cells

About 40% of bone marrow-derived dendritic cells (BM-DCs) generated from stem cells of C57BL/6 (B6.WT) mice differentiate in the presence of granulocyte macrophage-colony stimulating factor (GM-CSF) without further stimuli to mature DCs. These cells are characterized by high levels of major histocompatibility complex class II, CD40, and CD86 on their surface. Recent studies have revealed that tumor necrosis factor (TNF) is crucial for maturation of BM-DCs. However, once matured, the phenotype of mature TNF-negative C57BL/6 (B6.TNF-/-) and B6.WT BM-DCs is comparable. Both expressed high levels of CD40 and CD86 and were positive for mRNA of the chemokine receptor (CCR)7. To extend our studies, we generated a monoclonal antibody (mAb) specific for mouse CCR7. This mAb allowed us to analyze the surface expression of CCR7 during maturation of B6.WT and B6.TNF-/- BM-DCs in the presence of GM-CSF and stimulated with TNF or lipopolysaccharide (LPS) and to compare it with the CCR7 expression on ex vivo-isolated splenic DCs with or without additional stimulation. Our results showed that CCR7 expression on murine BM-DCs is an indication of cell maturity. Incubation with LPS induced the maturation of all BM-DCs in culture but increased the number of mature CCR7+ splenic DCs only marginally.

Human monocyte-derived dendritic cells are chemoattracted to C3a after up-regulation of the C3a receptor with interferons

The anaphylatoxin C3a is an important inflammatory mediator in the innate and adaptive immune systems. Recent reports in various animal models have fostered the role of C3a in mediating allergic reactions such as pulmonary allergies. However, data in humans are limited and the cellular targets for C3a are not fully understood. We sought to explore human dendritic cells as a new target for C3a, because C3a receptor (C3aR) expression has been described on myeloid cells, and dendritic cells are likely make contact with C3a at sites of inflammatory reactions. In this study, we demonstrated the expression of the C3aR on human monocyte-derived dendritic cells (MoDC) and its up-regulation by interferon (IFN)-alpha, IFN-gamma and prostaglandin E2 (PGE2). The strongest up-regulation was yielded by the combination of IFN-alpha+ IFN-gamma. Tumour necrosis factor-alpha (TNF-alpha) down-regulated the C3aR. After up-regulation of the C3aR by IFN-alpha+ IFN-gamma, C3a significantly up-regulated the surface expression of CD54, CD83 and CD86, but not of CD40, CD80 or human leucocyte antigen (HLA)-DR. C3a had no effect on the production of interleukin (IL)-10 or IL-12p70, or on the capacity of MoDC to stimulate autologous T-cell proliferation. However, C3a had a direct migratory effect on MoDC, as indicated by the induction of F-actin polymerization and migration in Boyden chamber experiments, which was pronounced after up-regulation of the C3aR with IFN-alpha+ IFN-gamma. Therefore, dendritic cells represent another group of target cells that might be recruited by C3a to areas of inflammation, in particular under conditions where IFNs are increased in the surrounding environment.

Up-regulation of C5a receptor expression and function on human monocyte derived dendritic cells by prostaglandin E2

The expression of the C5a-receptor (C5aR) on dendritic cells, its regulation and function have not been well established thus far. We show that the C5aR is expressed on human monocyte-derived dendritic cells (DC) and can be down-regulated by maturation stimuli such as tumour necrosis factor-alpha (TNF-alpha), lipopolysaccharide (LPS) or CD40L and by the T helper 1-cytokine interferon-gamma (INF-gamma). Prostaglandin E2 (PGE2), a proinflammatory mediator supporting dendritic cell activation and necessary for adequate DC migration, leads to the up-regulation of C5aR expression when incubated alone and prevents down-regulation when given in combination with TNF-alpha or LPS. Stimulation of C5aR on DC triggered F-actin polymerization, indicating the chemotactic potential of DC elicited by C5a. C5a induced F-actin polymerization was increased when C5aR was up-regulated by PGE2. Stimulation of DC with C5a resulted in interleukin-10 production which was significantly increased after C5aR up-regulation with TNF-alpha and PGE2. Therefore, up-regulation of the C5aR on human DC alters their chemotactic and immunologic response to C5a.

Anaphylatoxin C5a induces monocyte recruitment and differentiation into dendritic cells by TNF-alpha and prostaglandin E2-dependent mechanisms

Although monocytes can be directed to develop into dendritic cells (DC) in vitro, the molecular mechanisms that induce their transformation in vivo are largely unknown. In the present study we employed an in vivo SCID mouse model to investigate the impact of two proinflammatory chemotaxins, the anaphylatoxin C5a and the chemokine macrophage inflammatory protein-1alpha (CCL3), on the differentiation of human monocytes and immature DC generated from monocytes in the presence of GM-CSF and IL-4. Both C5a and macrophage inflammatory protein-1alpha recruited human monocytes and immature DC into the peritoneal cavity of SCID mice, but only C5a induced their differentiation into phenotypically mature DC by 48 h after injection. Macrophages derived from monocytes by in vitro culture were resistant to C5a-mediated transformation in vivo. The effect of C5a was indirect, since C5a-stimulated TNF-alpha and PGE(2) were found to be obligatory as well as sufficient to induce differentiation of monocytes. In contrast to monocytes, in vitro generated immature DC required TNF-alpha, but not PGE(2), for their C5a-mediated maturation in vivo. C5a-transformed monocytes represented an inflammatory type of DC, as they constitutively secreted high amounts of TNF-alpha, but also retained the capacity to release the Th1 cytokine IL-12 p70 upon stimulation with CD40 ligand. In summary, we identified for the first time a cascade of inflammatory signals that can induce the transformation of monocytes into DC in vivo. This novel function emphasizes the important immunoregulatory role of C5a at the interface of innate and adaptive immunity.

Characterization of C5aR expression on murine myeloid and lymphoid cells by the use of a novel monoclonal antibody

The anaphylatoxin C5a is a potent proinflammatory stimulus with immunomodulatory activities. Expression of its receptor C5aR (CD88) has been detected on cells of myeloid origin such as granulocytes and monocytes/macrophages. However, controversial results exist on the expression of C5aR on T and B lymphocytes as well as on mature dendritic cells (DC). The aim of the present study was to characterize expression of C5aR protein on myeloid and lymphoid cells in the mouse. For this purpose, rat monoclonal antibodies with specificity against the murine C5aR were generated. Using these reagents a distinct amount of C5aR antigen was observed on neutrophils and macrophages. In contrast, C5aR protein was not detectable on resting or stimulated murine T or B lymphocytes. Furthermore, no C5aR protein could be observed on splenic CD11c positive DC which have been classified in the literature as relatively mature. Taken together, our results suggest that in the mouse expression of C5aR protein may be restricted to leukocytes of myeloid origin whereas previous evidence for C5aR expression on lymphoid cells may be reevaluated.

IL-4 down-regulates anaphylatoxin receptors in monocytes and dendritic cells and impairs anaphylatoxin-induced migration in vivo

Anaphylatoxins mobilize leukocytes to the sites of inflammation. In the present study we investigated the impact of GM-CSF, IL-4, and IFN-gamma on anaphylatoxin receptor expression in monocytes and dendritic cells (DC). IL-4 was identified as the strongest down-regulator of the receptors for C5a and C3a in monocytes and monocyte-derived DC (MoDC). To study the impact of IL-4 on anaphylatoxin-induced chemotaxis, an in vivo migration model was established. For this purpose, human monocytes and MoDC were injected i.v. into SCID mice that at the same time received anaphylatoxins into the peritoneal cavity. A peritoneal influx of human monocytes could be demonstrated by 4 h after injections of C5a and C3a. In line with receptor down-regulation, IL-4 treatment inhibited in vivo mobilization of human monocytes and MoDC in response to C5a and C3a. In addition to its effects on human cells, IL-4 reduced C5a receptors in murine bone marrow-derived DC and impaired recruitment of labeled bone marrow-derived DC in syngeneic BALB/c mice to i.p. injected C5a. Overall, these data suggest that inhibition of a rapid anaphylatoxin-induced mobilization of monocytes and DC to inflamed tissues represents an important anti-inflammatory activity of the Th2 cytokine IL-4.

C5a anaphylatoxin is a major regulator of activating versus inhibitory FcgammaRs in immune complex-induced lung disease

IgG Fc receptors (FcgammaRs, especially FcgammaRIII) and complement (in particular, C5a anaphylatoxin) are critical effectors of the acute inflammatory response to immune complexes (ICs). However, it is unknown whether and how these two key components can interact with each other in vivo. We use here a mouse model of the acute pulmonary IC hypersensitivity reaction to analyze their potential interaction. FcgammaRIII and C5aR are coexpressed on alveolar macrophages (AMs), and both FcgammaRIII and C5aR mutant mice display impaired immune responses. We find that recombinant human C5a (rhC5a) can control inverse expression of various FcgammaRs, and costimulation of ICs with rhC5a results in strong enhancement of FcgammaRIII-triggered cellular activation in vitro and in vivo. Moreover, we show here that early IC-induced bioactive C5a, and its interaction with C5aR, causes induction of activating FcgammaRIII and suppression of inhibitory FcgammaRII on AMs that appears crucial for efficient cytokine production and neutrophil recruitment in lung pathology. Therefore, C5a, which is a potent chemoattractant, has a broader critical function in regulating the inhibitory/activating FcgammaRII/III receptor pair to connect complement and FcgammaR effector pathways in immune inflammation.

C5a anaphylatoxin is a major regulator of activating versus inhibitory FcgammaRs in immune complex-induced lung disease

IgG Fc receptors (FcgammaRs, especially FcgammaRIII) and complement (in particular, C5a anaphylatoxin) are critical effectors of the acute inflammatory response to immune complexes (ICs). However, it is unknown whether and how these two key components can interact with each other in vivo. We use here a mouse model of the acute pulmonary IC hypersensitivity reaction to analyze their potential interaction. FcgammaRIII and C5aR are coexpressed on alveolar macrophages (AMs), and both FcgammaRIII and C5aR mutant mice display impaired immune responses. We find that recombinant human C5a (rhC5a) can control inverse expression of various FcgammaRs, and costimulation of ICs with rhC5a results in strong enhancement of FcgammaRIII-triggered cellular activation in vitro and in vivo. Moreover, we show here that early IC-induced bioactive C5a, and its interaction with C5aR, causes induction of activating FcgammaRIII and suppression of inhibitory FcgammaRII on AMs that appears crucial for efficient cytokine production and neutrophil recruitment in lung pathology. Therefore, C5a, which is a potent chemoattractant, has a broader critical function in regulating the inhibitory/activating FcgammaRII/III receptor pair to connect complement and FcgammaR effector pathways in immune inflammation.

6-Sulfo LacNAc, a novel carbohydrate modification of PSGL-1, defines an inflammatory type of human dendritic cells

The monoclonal antibody M-DC8 defines a major subset of human blood dendritic cells (DCs). Here we identify the M-DC8 structure as 6-sulfo LacNAc, a novel carbohydrate modification of the P selectin glycoprotein ligand 1 (PSGL-1). In contrast to previously described blood DCs, M-DC8+ DCs lack the cutaneous lymphocyte antigen (CLA) on PSGL-1 and fail to bind P and E selectin. Yet they express anaphylatoxin receptors (C5aR and C3aR) and the Fcgamma receptor III (CD16), which recruit cells to inflammatory sites. While sharing with DC1 the expression of myeloid markers and a potent capacity to prime T cells in vitro, M-DC8+ DCs produce far more TNF-alpha in response to the bacterial endotoxin lipopolysaccharide (LPS). Thus, 6-sulfo LacNAc-expressing DCs appear as a novel proinflammatory DC subset.

Quantitative, phenotypic, and functional evaluation of basophils in myelodysplastic syndromes

BACKGROUND

The myelodysplastic syndromes (MDS) are a group of clonal haematological disorders characterized by cytopenia(s), reduced differentiation-capacity of myeloid cells, and impaired leukocyte function. However, little is known so far about basophil granulocytes in MDS.

DESIGN

We have compared the numbers, phenotype and function of basophils in MDS patients with those in healthy subjects. A total numer of 23 patients with MDS (refractory anaemia, n = 8; refractory anaemia with ringsideroblasts, n = 7; refractory anaemia with excess of blasts/refractory anaemia with excess of blasts in transformation, n = 8) and 20 healthy donors were included.

RESULTS

The numbers of blood basophils in MDS patients (34.6 +/- 62.9 microL-1) was lower compared to healthy controls (58.6 +/- 64.9 microL-1). Correspondingly, whole blood histamine levels were lower in MDS patients (MDS 34.1 +/- 29.1 ng mL-1 vs. normal donors 72.0 +/- 36.9 ng mL-1). Like "normal" basophils, basophils in MDS expressed interleukin-3 receptor alpha (CD123), E-NPP3 (CD203c), CR1 (CD35), CR3 (CD11b), CR4 (CD11c), membrane co-factor protein (CD46), decay-accelerating factor (CD55) and membrane attack complex inhibitory factor (CD59), as well as receptors for C3a, C5a (CD88), and IgE. Recombinant human (rh) C5a and anti-IgE induced significant release of histamine from basophils in both groups of donors without significant differences between MDS and healthy controls.

CONCLUSIONS

The absolute numbers of basophils in MDS patients are lower than in normal donors. However, basophils in MDS do not differ from their "normal counterparts" in terms of complement receptor expression, IgE-receptor expression, or functional responses to respective ligands.

Detection of anaphylatoxin receptors on CD83+ dendritic cells derived from human skin

Dendritic cells (DC) are recruited to sites of inflammation for the initiation of immune responses. As the anaphylatoxins C5a and C3a are important mediators of inflammation, we investigated the expression of their receptors (C3aR and C5aR) on human DC. DC were isolated from human skin or generated from purified blood monocytes and were identified by their expression of CD1a or CD83. Freshly isolated or cultured dermal CD1a+ and CD83+ DC bound anti-C5aR and anti-C3aR monoclonal antibodies (mAbs), as detected by flow cytometry. C5a induced calcium fluxes in dermal CD1a+ and CD83+ DC, which could be inhibited by C17/5, an anti-C5a mAb. C3a did not induce calcium fluxes in these cells. Anaphylatoxin receptor expression was down-regulated on dermal DC by adding tumour necrosis factor-alpha (TNF-alpha) to the culture medium. On CD1a+ CD83- cells generated from isolated blood monocytes by culture with 6.25 ng/ml of granulocyte-macrophage colony-stimulating factor (GM-CSF) and 125 U/ml of interleukin-4 (IL-4), expression of both C5aR and C3aR was observed. In these cells, both C5a and C3a induced calcium fluxes. After addition of TNF-alpha to the culture medium, the majority of the CD1a+ cells expressed CD83+. These cells - expressing a phenotype of 'mature DC' - down-regulated the expression of the anaphylatoxin receptors and lost their reactivity to the respective ligands. Our results demonstrate the expression of the anaphylatoxin receptors C5aR and C3aR on human skin-derived DC and blood-derived cells expressing the DC-associated membrane molecule, CD1a. Furthermore, the expression of anaphylatoxin receptors on CD83+ dermal DC is indicative of an intermediate stage of maturation of these cells, which was not observed on in vitro-differentiated CD83+ cells.

C5a and C5a(desArg) enhance the susceptibility of monocyte-derived macrophages to HIV infection

Mononuclear phagocytes, which include circulating blood monocytes and differentiated tissue macrophages, are believed to play a central role in the sexual transmission of HIV infection. The ability of HIV to productively infect these cells may be influenced by action of exogenous or host-derived substances at the site of viral entry. Given the potent capacities of inflammatory mediators to stimulate anaphylatoxic and immunomodulatory functions in mucosa, the effects of complement-derived anaphylatoxins on the susceptibility of monocytes and monocyte-derived macrophages (MDM) to HIV-1 infection were examined. In our in vitro system, the susceptibility to infection was up to 40 times increased in MDM that had been exposed to C5a or C5a(desArg), but not to C3a or C3a(desArg), for 2 days before adding of virus. By contrast, the treatment with complement anaphylatoxins did not affect HIV replication in fresh monocytes. Stimulatory effect of C5a and its desArg derivative on HIV infection correlated with the increase of TNF-alpha and IL-6 secretion from MDM. All these functional effects of C5a and C5a(desArg) were reversible by treatment of cells with the mAb that functionally blocks C5aR. Taken together, these results indicate that C5a and C5a(desArg) may increase the susceptibility of MDM to HIV infection through stimulation of TNF-alpha and IL-6 secretion from these cells.

Activated human T lymphocytes express a functional C3a receptor

The C3a molecule is an anaphylatoxin of the C system with a wide spectrum of proinflammatory effects predominantly on cells of myeloid origin. In this study we investigated the expression of the high affinity receptor for C3a (C3aR) in human T lymphocytes using receptor-specific mAb. C3aR expression was detected in CD4(+) and CD8(+) blood- or skin-derived T cell clones (TCC) from birch pollen-sensitized patients with atopic dermatitis. No significant difference in C3aR expression in CD4(+) or CD8(+) TCCs could be observed. In contrast to C3a(desArg), C3a led to a transient calcium flux in TCCs expressing the C3aR, whereas C3aR-negative TCCs were unreactive. Circulating T cells from patients suffering from severe inflammatory skin diseases expressed the C3aR, whereas no expression of C3aR could be found in unstimulated T lymphocytes from patients with mild inflammatory skin diseases or from healthy individuals. Type I IFNs, which are potent stimulators of cellular immunity, were identified as up-regulators of C3aR expression in vitro in freshly isolated or cloned T lymphocytes. Moreover, C3aR(+) T cells were found at the sites of injection in IFN-beta-treated patients with multiple sclerosis. These data provide direct evidence for the expression of C3aR on activated human T lymphocytes; this may point to a biological function of C3a in T cell-dependent diseases.

The C5a receptor is expressed in normal renal proximal tubular but not in normal pulmonary or hepatic epithelial cells

C5a, a 74 amino acid peptide cleaved from the complement protein C5, is an extremely potent anaphylatoxin. Expression of the receptor for the anaphylatoxin C5a (C5aR) has been thought to be restricted to cells of myeloid origin. However, recent evidence suggests that the C5aR is also expressed in hepatocytes as well as in pulmonary epithelial, endothelial and smooth muscle cells. In the present study, we investigated the tissue distribution of C5aR by immunohistochemistry in normal human lung, liver, intestine and kidney using well-defined monoclonal antibodies (mAbs) directed against the extracellular N-terminus of the receptor. In all tissues examined, macrophages displayed an abundant expression of C5aR protein. However, in the normal human lung, C5aR expression was not detectable in bronchial and alveolar epithelial cells or in vascular smooth muscle or endothelial cells. In the normal human liver, no C5aR protein was detected in hepatocytes, whereas Kupffer cells strongly expressed the C5aR. In normal human kidney, the C5aR was detectable only in proximal tubular cells. C5aR gene transcription in Kupffer cells and proximal tubular cells was confirmed by in situ hybridization. Thus, our results point to an as yet unknown role of the C5aR in normal renal physiology. In the normal lung and liver, however, previous evidence for the ubiquitous expression of C5aR in epithelial, endothelial and smooth muscle cells in situ should be re-evaluated.