Consistent Site-Specific Foraging Behaviours of Yellow-eyed Penguins/Hoiho Breeding on Stewart Island, New Zealand

Simple Summary

The yellow-eyed penguin (Megadyptes antipodes) is endemic to New Zealand and has declined c. 72% since 2008/09 within its mainland range. Population monitoring suggests yellow-eyed penguins are tracking below even the most pessimistic scenario modelled, indicating stressors may not be accurately quantified or underestimated. Fisheries-related bycatch, particularly in gillnets, has been identified as a significant contributor to the species’ decline. Mortality mitigation measures exist for penguins breeding on South Island, with a four nautical mile gillnet exclusion zone in place. Penguins breeding on Stewart Island have no protection, leaving them vulnerable to capture and drowning in gillnets. We use GPS-TDR loggers attached to adult breeding penguins from three sites across Stewart Island to track their at-sea activity, diving behaviour, and investigate the degree of foraging plasticity displayed across this range. Penguins from each site showed significant differences in their preferred habitat use and were consistent between trips and years. Results here show that foraging locations at one site cannot be used to assess habitat use by penguins at other sites. The intra-site and inter-annual consistency in preferred foraging locations observed in Stewart Island penguins reveal that implementation of marine protection may be effective in eliminating fisheries-related mortality and reduce the risk of local extinction.

Abstract

The endangered yellow-eyed penguin/hoiho (Megadyptes antipodes) predominantly forages benthically within its mainland range and shows high foraging site fidelity. Identifying consistencies in foraging locations can allow effective conservation, especially when managing bycatch risk. This study investigated the at-sea distribution of penguins breeding on Stewart Island to explore site-specific foraging strategies and inform fisheries management. During the 2020/21 season, 19 adult breeding yellow-eyed penguins from Port Pegasus, Paterson Inlet, and Codfish Island were fitted with GPS-TDR dive loggers to track their movements and diving behaviours. A total of 25,696 dives were recorded across 91 foraging trips. Birds from Port Pegasus reached significantly greater depths, spent longer at the seafloor, and performed longer dives. They also had the smallest foraging distribution, with most activity concentrated inshore. Compared to Port Pegasus, foraging radii and trip lengths were twice as large for Paterson Inlet and four times larger at Codfish Island. Despite differences in available foraging habitat, considerable individual and intra-site consistency for preferred foraging locations was observed. Localised behaviour and inter-site differences in dive metrics suggest significant plasticity in foraging ecology across their mainland range; however, individual behaviour and preferred foraging locations were extremely predictable. Thus, risk of mortality from fisheries can be quantified and managed accordingly.

The role of allochrony in influencing interspecific differences in foraging distribution during the non-breeding season between two congeneric crested penguin species

Mechanisms promoting coexistence between closely related species are fundamental for maintaining species diversity. Mechanisms of niche differentiation include allochrony which offsets the peak timing of resource utilisation between species. Many studies focus on spatial and temporal niche partitioning during the breeding season, few have investigated the role allochrony plays in influencing interspecific segregation of foraging distribution and ecology between congeneric species during the non-breeding season. We investigated the non-breeding migrations of Snares (Eudyptes robustus) and Fiordland penguins (Eudyptes pachyrhynchus), closely related species breeding between 100-350 km apart whose migration phenology differs by two months. Using light geolocation tracking, we examined the degree of overlap given the observed allochrony and a hypothetical scenario where the species commence migration simultaneously. We found that Fiordland penguins migrated to the Sub-Antarctic Frontal Zone and Polar Frontal Zone in the austral autumn whereas Snares penguins disperse westwards staying north of the Sub-Tropical Front in the austral winter. Our results suggest that allochrony is likely to be at the root of segregation because the relative profitability of the different water masses that the penguins forage in changes seasonally which results in the two species utilising different areas over their core non-breeding periods. Furthermore, allochrony reduces relatively higher levels of spatiotemporal overlap during the departure and arrival periods, when the close proximity of the two species' colonies would cause the birds to congregate in similar areas, resulting in high interspecific competition just before the breeding season. Available evidence from other studies suggests that the shift in phenology between these species has arisen from adaptive radiation and phenological matching to the seasonality of local resource availability during the breeding season and reduced competitive overlap over the non-breeding season is likely to be an incidental outcome.

How animals distribute themselves in space: energy landscapes of Antarctic avian predators

BACKGROUND

Energy landscapes provide an approach to the mechanistic basis of spatial ecology and decision-making in animals. This is based on the quantification of the variation in the energy costs of movements through a given environment, as well as how these costs vary in time and for different animal populations. Organisms as diverse as fish, mammals, and birds will move in areas of the energy landscape that result in minimised costs and maximised energy gain. Recently, energy landscapes have been used to link energy gain and variable energy costs of foraging to breeding success, revealing their potential use for understanding demographic changes.

METHODS

Using GPS-temperature-depth and tri-axial accelerometer loggers, stable isotope and molecular analyses of the diet, and leucocyte counts, we studied the response of gentoo (Pygoscelis papua) and chinstrap (Pygoscelis antarcticus) penguins to different energy landscapes and resources. We compared species and gentoo penguin populations with contrasting population trends.

RESULTS

Between populations, gentoo penguins from Livingston Island (Antarctica), a site with positive population trends, foraged in energy landscape sectors that implied lower foraging costs per energy gained compared with those around New Island (Falkland/Malvinas Islands; sub-Antarctic), a breeding site with fluctuating energy costs of foraging, breeding success and populations. Between species, chinstrap penguins foraged in sectors of the energy landscape with lower foraging costs per bottom time, a proxy for energy gain. They also showed lower physiological stress, as revealed by leucocyte counts, and higher breeding success than gentoo penguins. In terms of diet, we found a flexible foraging ecology in gentoo penguins but a narrow foraging niche for chinstraps.

CONCLUSIONS

The lower foraging costs incurred by the gentoo penguins from Livingston, may favour a higher breeding success that would explain the species' positive population trend in the Antarctic Peninsula. The lower foraging costs in chinstrap penguins may also explain their higher breeding success, compared to gentoos from Antarctica but not their negative population trend. Altogether, our results suggest a link between energy landscapes and breeding success mediated by the physiological condition.

High-coverage genomes to elucidate the evolution of penguins

BACKGROUND

Penguins (Sphenisciformes) are a remarkable order of flightless wing-propelled diving seabirds distributed widely across the southern hemisphere. They share a volant common ancestor with Procellariiformes close to the Cretaceous-Paleogene boundary (66 million years ago) and subsequently lost the ability to fly but enhanced their diving capabilities. With ∼20 species among 6 genera, penguins range from the tropical Galápagos Islands to the oceanic temperate forests of New Zealand, the rocky coastlines of the sub-Antarctic islands, and the sea ice around Antarctica. To inhabit such diverse and extreme environments, penguins evolved many physiological and morphological adaptations. However, they are also highly sensitive to climate change. Therefore, penguins provide an exciting target system for understanding the evolutionary processes of speciation, adaptation, and demography. Genomic data are an emerging resource for addressing questions about such processes.

RESULTS

Here we present a novel dataset of 19 high-coverage genomes that, together with 2 previously published genomes, encompass all extant penguin species. We also present a well-supported phylogeny to clarify the relationships among penguins. In contrast to recent studies, our results demonstrate that the genus Aptenodytes is basal and sister to all other extant penguin genera, providing intriguing new insights into the adaptation of penguins to Antarctica. As such, our dataset provides a novel resource for understanding the evolutionary history of penguins as a clade, as well as the fine-scale relationships of individual penguin lineages. Against this background, we introduce a major consortium of international scientists dedicated to studying these genomes. Moreover, we highlight emerging issues regarding ensuring legal and respectful indigenous consultation, particularly for genomic data originating from New Zealand Taonga species.

CONCLUSIONS

We believe that our dataset and project will be important for understanding evolution, increasing cultural heritage and guiding the conservation of this iconic southern hemisphere species assemblage.

Ancient DNA of crested penguins: Testing for temporal genetic shifts in the world's most diverse penguin clade

Human impacts have substantially reduced avian biodiversity in many parts of the world, particularly on isolated islands of the Pacific Ocean. The New Zealand archipelago, including its five subantarctic island groups, holds breeding grounds for a third of the world's penguin species, including several representatives of the diverse crested penguin genus Eudyptes. While this species-rich genus has been little studied genetically, recent population estimates indicate that several Eudyptes taxa are experiencing demographic declines. Although crested penguins are currently limited to southern regions of the New Zealand archipelago, prehistoric fossil and archaeological deposits suggest a wider distribution during prehistoric times, with breeding ranges perhaps extending to the North Island. Here, we analyse ancient, historic and modern DNA sequences to explore two hypotheses regarding the recent history of Eudyptes in New Zealand, testing for (1) human-driven extinction of Eudyptes lineages; and (2) reduced genetic diversity in surviving lineages. From 83 prehistoric bone samples, each tentatively identified as 'Eudyptes spp.', we genetically identified six prehistoric penguin taxa from mainland New Zealand, including one previously undescribed genetic lineage. Moreover, our Bayesian coalescent analyses indicated that, while the range of Fiordland crested penguin (E. pachyrhynchus) may have contracted markedly over the last millennium, genetic DNA diversity within this lineage has remained relatively constant. This result contrasts with human-driven biodiversity reductions previously detected in several New Zealand coastal vertebrate taxa.

High definition video loggers provide new insights into behaviour, physiology, and the oceanic habitat of a marine predator, the yellow-eyed penguin

Camera loggers are increasingly used to examine behavioural aspects of free-ranging animals. However, often video loggers are deployed with a focus on specific behavioural traits utilizing small cameras with a limited field of view, poor light performance and video quality. Yet rapid developments in consumer electronics provide new devices with much improved visual data allowing a wider scope for studies employing this novel methodology. We developed a camera logger that records full HD video through a wide-angle lens, providing high resolution footage with a greater field of view than other camera loggers. The main goal was to assess the suitability of this type of camera for the analysis of various aspects of the foraging ecology of a marine predator, the yellow-eyed penguin in New Zealand. Frame-by-frame analysis allowed accurate timing of prey pursuits and time spent over certain seafloor types. The recorded video footage showed that prey species were associated with certain seafloor types, revealed different predator evasion strategies by benthic fishes, and highlighted varying energetic consequences for penguins pursuing certain types of prey. Other aspects that could be analysed were the timing of breathing intervals between dives and observe exhalation events during prey pursuits, a previously undescribed behaviour. Screen overlays facilitated analysis of flipper angles and beat frequencies throughout various stages of the dive cycle. Flipper movement analysis confirmed decreasing effort during descent phases as the bird gained depth, and that ascent was principally passive. Breathing episodes between dives were short (<1 s) while the majority of the time was devoted to subsurface scanning with a submerged head. Video data recorded on free-ranging animals not only provide a wealth of information recorded from a single deployment but also necessitate new approaches with regards to analysis of visual data. Here, we demonstrate the diversity of information that can be gleaned from video logger data, if devices with high video resolution and wide field of view are utilized.

High definition video loggers provide new insights into behaviour, physiology, and the oceanic habitat of a marine predator, the yellow-eyed penguin

Camera loggers are increasingly used to examine behavioural aspects of free-ranging animals. However, often video loggers are deployed with a focus on specific behavioural traits utilizing small cameras with a limited field of view, poor light performance and video quality. Yet rapid developments in consumer electronics provide new devices with much improved visual data allowing a wider scope for studies employing this novel methodology. We developed a camera logger that records full HD video through a wide-angle lens, providing high resolution footage with a greater field of view than other camera loggers. The main goal was to assess the suitability of this type of camera for the analysis of various aspects of the foraging ecology of a marine predator, the yellow-eyed penguin in New Zealand. Frame-by-frame analysis allowed accurate timing of prey pursuits and time spent over certain seafloor types. The recorded video footage showed that prey species were associated with certain seafloor types, revealed different predator evasion strategies by benthic fishes, and highlighted varying energetic consequences for penguins pursuing certain types of prey. Other aspects that could be analysed were the timing of breathing intervals between dives and observe exhalation events during prey pursuits, a previously undescribed behaviour. Screen overlays facilitated analysis of flipper angles and beat frequencies throughout various stages of the dive cycle. Flipper movement analysis confirmed decreasing effort during descent phases as the bird gained depth, and that ascent was principally passive. Breathing episodes between dives were short (<1 s) while the majority of the time was devoted to subsurface scanning with a submerged head. Video data recorded on free-ranging animals not only provide a wealth of information recorded from a single deployment but also necessitate new approaches with regards to analysis of visual data. Here, we demonstrate the diversity of information that can be gleaned from video logger data, if devices with high video resolution and wide field of view are utilized.

Marathon penguins - Reasons and consequences of long-range dispersal in Fiordland penguins / Tawaki during the pre-moult period

Migratory species often roam vast distances bringing them into contact with diverse conditions and threats that could play significant roles in their population dynamics. This is especially true if long-range travels occur within crucial stages of a species’ annual life-cycle. Crested penguins, for example, usually disperse over several hundreds of kilometres after completing the energetically demanding breeding season and in preparation for the costly annual moult. A basic understanding of crested penguins’ pre-moult dispersal is therefore paramount in order to be able to assess factors affecting individual survival. The Fiordland penguin, or Tawaki, the only crested penguin species breeding on the New Zealand mainland, is currently one of the least studied and rarest penguin species in the world. We successfully satellite tracked the pre-moult dispersal of 17 adult Tawaki from a single colony located in the species’ northern breeding distribution. Over the course of 8–10 weeks the penguins travelled up to 2,500 km away from their breeding colony, covering total swimming distances of up to 6,800 km. During outbound travels all penguins headed south-west within a well-defined corridor before branching out towards two general trip destinations. Birds leaving in late November travelled towards the Subtropical Front some 800 km south of Tasmania, whereas penguins that left in December headed further towards the subantarctic front. Using K-select analysis we examined the influence of oceanographic factors on the penguins’ dispersal. Water depth, surface current velocity and sea level anomalies had the greatest influence on penguin movements at the subantarctic Front, while sea surface temperature and chlorophyll a concentration were key for birds travelling to the subtropical front. We discuss our findings in the light of anthropogenic activities (or lack thereof) in the regions visited by the penguins as well as the potential consequences of Tawaki pre-moult dispersal for the species’ breeding distribution on the New Zealand mainland.

How animals distribute themselves in space: variable energy landscapes

BACKGROUND

Foraging efficiency determines whether animals will be able to raise healthy broods, maintain their own condition, avoid predators and ultimately increase their fitness. Using accelerometers and GPS loggers, features of the habitat and the way animals deal with variable conditions can be translated into energetic costs of movement, which, in turn, can be translated to energy landscapes.We investigated energy landscapes in Gentoo Penguins Pygoscelis papua from two colonies at New Island, Falkland/Malvinas Islands.

RESULTS

In our study, the marine areas used by the penguins, parameters of dive depth and the proportion of pelagic and benthic dives varied both between years and colonies. As a consequence, the energy landscapes also varied between the years, and we discuss how this was related to differences in food availability, which were also reflected in differences in carbon and nitrogen stable isotope values and isotopic niche metrics. In the second year, the energy landscape was characterized by lower foraging costs per energy gain, and breeding success was also higher in this year. Additionally, an area around three South American Fur Seal Arctocephalus australis colonies was never used.

CONCLUSIONS

These results confirm that energy landscapes vary in time and that the seabirds forage in areas of the energy landscapes that result in minimized energetic costs. Thus, our results support the view of energy landscapes and fear of predation as mechanisms underlying animal foraging behaviour. Furthermore, we show that energy landscapes are useful in linking energy gain and variable energy costs of foraging to breeding success.

Quantifying climate change impacts emphasises the importance of managing regional threats in the endangered Yellow-eyed penguin

Climate change is a global issue with effects that are difficult to manage at a regional scale. Yet more often than not climate factors are just some of multiple stressors affecting species on a population level. Non-climatic factors—especially those of anthropogenic origins—may play equally important roles with regard to impacts on species and are often more feasible to address. Here we assess the influence of climate change on population trends of the endangered Yellow-eyed penguin (Megadyptes antipodes) over the last 30 years, using a Bayesian model. Sea surface temperature (SST) proved to be the dominating factor influencing survival of both adult birds and fledglings. Increasing SST since the mid-1990s was accompanied by a reduction in survival rates and population decline. The population model showed that 33% of the variation in population numbers could be explained by SST alone, significantly increasing pressure on the penguin population. Consequently, the population becomes less resilient to non-climate related impacts, such as fisheries interactions, habitat degradation and human disturbance. However, the extent of the contribution of these factors to declining population trends is extremely difficult to assess principally due to the absence of quantifiable data, creating a discussion bias towards climate variables, and effectively distracting from non-climate factors that can be managed on a regional scale to ensure the viability of the population.

Pollution, habitat loss, fishing, and climate change as critical threats to penguins

Cumulative human impacts across the world's oceans are considerable. We therefore examined a single model taxonomic group, the penguins (Spheniscidae), to explore how marine species and communities might be at risk of decline or extinction in the southern hemisphere. We sought to determine the most important threats to penguins and to suggest means to mitigate these threats. Our review has relevance to other taxonomic groups in the southern hemisphere and in northern latitudes, where human impacts are greater. Our review was based on an expert assessment and literature review of all 18 penguin species; 49 scientists contributed to the process. For each penguin species, we considered their range and distribution, population trends, and main anthropogenic threats over the past approximately 250 years. These threats were harvesting adults for oil, skin, and feathers and as bait for crab and rock lobster fisheries; harvesting of eggs; terrestrial habitat degradation; marine pollution; fisheries bycatch and resource competition; environmental variability and climate change; and toxic algal poisoning and disease. Habitat loss, pollution, and fishing, all factors humans can readily mitigate, remain the primary threats for penguin species. Their future resilience to further climate change impacts will almost certainly depend on addressing current threats to existing habitat degradation on land and at sea. We suggest protection of breeding habitat, linked to the designation of appropriately scaled marine reserves, including in the High Seas, will be critical for the future conservation of penguins. However, large-scale conservation zones are not always practical or politically feasible and other ecosystem-based management methods that include spatial zoning, bycatch mitigation, and robust harvest control must be developed to maintain marine biodiversity and ensure that ecosystem functioning is maintained across a variety of scales.

Straight line foraging in yellow-eyed penguins: new insights into cascading fisheries effects and orientation capabilities of marine predators

Free-ranging marine predators rarely search for prey along straight lines because dynamic ocean processes usually require complex search strategies. If linear movement patterns occur they are usually associated with travelling events or migratory behaviour. However, recent fine scale tracking of flying seabirds has revealed straight-line movements while birds followed fishing vessels. Unlike flying seabirds, penguins are not known to target and follow fishing vessels. Yet yellow-eyed penguins from New Zealand often exhibit directed movement patterns while searching for prey at the seafloor, a behaviour that seems to contradict common movement ecology theories. While deploying GPS dive loggers on yellow-eyed penguins from the Otago Peninsula we found that the birds frequently followed straight lines for several kilometres with little horizontal deviation. In several cases individuals swam up and down the same line, while some of the lines were followed by more than one individual. Using a remote operated vehicle (ROV) we found a highly visible furrow on the seafloor most likely caused by an otter board of a demersal fish trawl, which ran in a straight line exactly matching the trajectory of a recent line identified from penguin tracks. We noted high abundances of benthic scavengers associated with fisheries-related bottom disturbance. While our data demonstrate the acute way-finding capabilities of benthic foraging yellow-eyed penguins, they also highlight how hidden cascading effects of coastal fisheries may alter behaviour and potentially even population dynamics of marine predators, an often overlooked fact in the examination of fisheries’ impacts.

Heart rate responses provide an objective evaluation of human disturbance stimuli in breeding birds

Intuition is a poor guide for evaluating the effects of human disturbance on wildlife. Using the endangered Yellow-eyed penguin, Megadyptes antipodes, as an example, we show that heart rate responses provide an objective tool to evaluate human disturbance stimuli and encourage the wider use of this simple and low-impact approach. Yellow-eyed penguins are a flagship species for New Zealand's wildlife tourism; however, unregulated visitor access has recently been associated with reduced breeding success and lower first year survival. We measured heart rate responses of Yellow-eyed penguins via artificial eggs to evaluate a range of human stimuli regularly occurring at their breeding sites. We found the duration of a stimulus to be the most important factor, with elevated heart rate being sustained while a person remained within sight. Human activity was the next important component; a simulated wildlife photographer, crawling slowly around during his stay, elicited a significantly higher heart rate response than an entirely motionless human spending the same time at the same distance. Stimuli we subjectively might perceive as low impact, such as the careful approach of a 'wildlife photographer', resulted in a stronger response than a routine nest-check that involved lifting a bird up to view nest contents. A single, slow-moving human spending 20 min within 2 m from the nest may provoke a response comparable to that of 10 min handling a bird for logger deployment. To reduce cumulative impact of disturbance, any human presence in the proximity of Yellow-eyed penguins needs to be kept at a minimum. Our results highlight the need for objective quantification of the effects of human disturbance in order to provide a sound basis for guidelines to manage human activity around breeding birds.

Induction of proliferation and cytokine production in human T lymphocytes by lipopolysaccharide (LPS)

Lipopolysaccharide (LPS), also known as endotoxin, is a compound of the cell wall of Gram-negative bacteria, which has been demonstrated to induce inflammatory reactions in vitro as well as in vivo, including lethal shock. A great number of different cells have been documented to be reactive to LPS, e.g. monocytes/macrophages, vascular cells, polymorphonuclear cells, and even B lymphocytes. We have now established that T lymphocytes could also contribute to an inflammatory reaction to LPS. LPS is a potent inducer of human T-lymphocyte proliferation and cytokine production. The activation of T lymphocytes by LPS requires direct cell-to-cell contact with viable accessory monocytes. This interaction was found to be MHC-unrestricted, but strongly dependent on costimulatory signals provided by B7/CD28 interactions. The frequency of responding T lymphocytes is less than 1:1000. A very exciting finding was that not only monocytes, but also CD34+ hematopoietic stem cells, which circulate in peripheral blood in very low frequency, exert essential accessory cell activity during stimulation of T lymphocytes by LPS. In contrast, the response of T lymphocytes to conventional recall antigens is not controlled by blood stem cells. These conclusions are based on the observation that depletion of CD34-positive blood stem cells resulted in a complete loss of LPS-induced T-lymphocyte stimulation. Addition of CD34-enriched blood stem cells led to a recovery of reactivity of T lymphocyte to LPS. The characteristics of T-lymphocyte activation indicate that LPS is neither active as a mitogen, or as a superantigen, or as a classical antigen, but may activate T lymphocyte through a new, so far undescribed, mechanism. Furthermore, the involvement of hematopoietic blood stem cells in the activation of T lymphocytes by LPS demonstrates a role of these cells in inflammatory and immunological events.

In vitro generation of bacillus Calmette-Guérin-activated killer cells

Tumor regression induced in cancer patients by local instillation of bacillus Calmette-Guérin (BCG) into the bladder is considered to be mediated by cellular immune and inflammatory reactions. In an attempt to elucidate which of these effects are relevant to tumoricidal activity, an in vitro system was employed in which the immunostimulatory effects of BCG could be studied. This report describes the induction of BCG-activated killer (BAK) cells, which effectively lyse bladder tumor cells. Human peripheral blood mononuclear cells (PBMC) were stimulated with viable and sonicated BCG (v-BCG and s-BCG, respectively) to generate BAK cells. Cytotoxicity of BAK cells was comparable with the cytotoxicity exerted by lymphokine-activated killer (LAK) cells generated by interferon (IFN)-gamma but did not reach the level of interleukin-2 (IL-2)-generated LAK cells. Induction of BAK cells was possible only with v-BCG and not with s-BCG. By depletion and enrichment of defined cell populations, the cytotoxic potential of BAK cells could be attributed to a population of CD8(+) and CD56(+) double-positive lymphocytes. Macrophages and CD4(+) cells were required for the induction of killing activity but had no such activity by themselves. Furthermore, the presence of IFN-gamma and IL-2 in the supernatants harvested during the generation of BAK cells was demonstrated. Monoclonal antibodies neutralizing these cytokines abolished BCG-mediated cytotoxicity. From these results, it is concluded that the known beneficial effect of local instillation of BCG on maintenance of the relapse-free state in superficial bladder cancer may be due to local generation of BAK cells.

Lipopolysaccharide and peptidoglycan: CD14-dependent bacterial inducers of inflammation

Surface structures of bacteria contribute to the microbial pathogenic potential and are capable of causing local and generalized inflammatory reactions. Among these factors, endotoxin and peptidoglycan are of particular medical importance. Both toxic bacterial polymers are now recognized to interact with the same cellular receptor, the CD14 molecule, which is expressed on different types of immune cells, in particular, monocytes/macrophages. The interaction between these bacterial activators and CD14 leads to the production of endogenous mediators such as tumor necrosis factor alpha, interleukin 1 (IL-1), and IL-6, which are ultimately responsible for phlogistic responses. The fact that CD14 recognizes not only endotoxin and peptidoglycan but also other glycosyl-based microbial polymers suggests that this cellular surface molecule represents a lectin.

CD34(+) hematopoietic stem cells exert accessory function in lipopolysaccharide-induced T cell stimulation and CD80 expression on monocytes

CD34(+) hematopoietic stem cells, which circulate in peripheral blood with very low frequency, exert essential accessory function during lipopolysaccharide (LPS)-induced human T lymphocyte activation, resulting in interferon gamma production and proliferation. In contrast, stimulation of T cells by "conventional" recall antigens is not controlled by blood stem cells. These conclusions are based on the observation that depletion of CD34(+) blood stem cells results in a loss of LPS-induced T cell stimulation as well as reduced expression of CD80 antigen on monocytes. The addition of CD34-enriched blood stem cells resulted in a recovery of reactivity of T cells and monocytes to LPS. Blood stem cells could be replaced by the hematopoietic stem cell line KG-1a. These findings may be of relevance for high risk patients treated with stem cells or stem cell recruiting compounds and for patients suffering from endotoxin-mediated diseases.

Stimulation of human T lymphocytes by LPS is MHC unrestricted, but strongly dependent on B7 interactions

Recently, we have shown that LPS is a potent inducer of human T cell proliferation and lymphokine production. However, the activation of T cells by LPS has been demonstrated to be monocyte dependent and to require direct cell-to-cell contact. Here, we investigated the role of monocytes as accessory cells and the requirement for costimulatory signals in more detail. We found that the accessory cell activity of monocytes during LPS-induced T cell proliferation is characterized by the following features: LPS-primed monocytes are competent stimulators of T cell proliferation; interaction of LPS with monocytes during the priming step is dependent on CD14 and is sensitive to ammonia; monocyte/T cell interactions are not MHC restricted but are strongly dependent on interactions of CD28 and/or CTLA-4 on T cells and their ligands CD80 and/or CD86 on monocytes. CD80 seems to be crucial for the activation of T cells by monocytes, since monocytes expressing CD86 but not CD80 after LPS stimulation were unable to stimulate T cells; IL-12, at least as a costimulatory factor, but not IL-15, is important in LPS-induced T cell proliferation. Taken together, our results indicate that LPS acts neither as a mitogen, nor as a superantigen, nor as an Ag. The activation of human T cells by LPS requires the help of accessory functions by primed monocytes and is MHC unrestricted but needs costimulatory signals via CD28 and/or CTLA-4.

Staining pattern of seven monoclonal anti-CD26 antibodies in leprosy: implications for the use of CD26 as a surrogate marker of a human Th1-like reaction

In a previous study using the monoclonal anti-CD26 antibody MIB-DS2/7 in leprosy and other granulomatous diseases, it was shown that CD26 may be a candidate for use as an operational marker of a human Th1-like reaction. In this follow-up study, we compared seven different monoclonal anti-CD26 antibodies with respect to their staining pattern in lepromatous and tuberculoid leprosy tissues. Three distinct staining patterns became apparent in this anti-CD26 antibody panel: staining of T-lymphocytes and of connective tissue; staining of T-lymphocytes, connective tissue and macrophages; and almost no staining of T-lymphocytes but staining of connective tissue and macrophages. The two antibodies assigned to the first staining pattern, including MIB-DS2/7, were found to be most suitable for the operational discrimination between Th1-like and Th2-like reactions in leprosy. The antibodies assigned to staining patterns 2 and 3 did not allow this discrimination. Although all seven monoclonal antibodies investigated were specific for CD26, only two were found to be useful in identifying a Th1-like immune reaction in human tissue.

CD26 (dipeptidyl peptidase i.v.) on human T lymphocytes does not mediate adhesion of these cells to endothelial cells or fibroblasts

We have examined the role of CD26 (dipeptidyl peptidase IV) in the adhesion of resting and activated T lymphocytes to endothelial cells and fibroblasts. For this purpose, we ran a short-time adhesion assay under different strategies: Adhesion of T lymphocytes was determined in the presence of different anti-CD26 monoclonal antibodies, or in the presence of synthetic inhibitors of the enzymatic function of CD26. In addition, the expression of CD26 on T lymphocytes, which were adherent to endothelial cells or fibroblasts, was performed by flow cytometric analysis. We found that the anti-CD26 monoclonal antibodies tested here were not able to inhibit T cell adhesion to monolayers of endothelial cells or fibroblasts. Secondly, synthetic inhibitors of the enzymatic function of CD26 had no effect on the adhesion of T lymphocytes to endothelial cells or fibroblasts. Furthermore, CD26-positive T cells were not accumulated in the adherent population. These results suggest that CD26 on T lymphocytes plays no role in T cell adhesion to endothelial cells or fibroblasts.

Comparative study of CD26 as a Th1-like and CD30 as a potential Th2-like operational marker in leprosy

In the last years we have been able to establish CD26 as an operational marker for a human Th1-like reaction in various granulomatous diseases. Recently, CD30 was described as a marker for a Th2-type reaction, where CD30 is preferentially expressed and its soluble form released by human T cell clones producing Th2-type cytokines. To evaluate the possibility of CD30 as an eventual operational marker for a human Th2-like reaction in vivo, we performed immunohistological stainings on frozen sections of skin biopsies from patients with lepromatous and tuberculoid leprosy. A maximum of three to four CD30-positive cells was found per section, and there was no difference in the accumulation of CD30-positive cells between the tuberculoid and the lepromatous form of leprosy. With respect to CD26-positive cells, a high number was found in tuberculoid leprosy in contrast to a greatly reduced expression of CD26 in lepromatous leprosy. We conclude that, while CD26 was confirmed as an operational marker for a Th1-like reaction in leprosy, CD30 does not represent an operational Th2 marker in this disease.

Antibody-induced modulation of CD26 surface expression

The ability of different anti-CD26 monoclonal antibodies to modulate the expression of CD26 on human T lymphocytes was investigated. By means of a new non-radioactive method using fluorescein isothiocyanate (FITC)-labelled and unlabelled anti-CD26 monoclonal antibodies and flow cytometry, we measured the internalization and re-expression of CD26 on freshly isolated resting human T lymphocytes. The modulation of CD26 surface expression takes place in primarily CD26+ as well as in CD26- T lymphocytes, indicating the presence of an intracellular CD26 pool. In fact, with two different anti-CD26 monoclonal antibodies (Ta1 and M5) intracellular CD26 was detected out of which newly expressed CD26 might have originated. This intracellular CD26 pool appears to be maintained by continuous translation of CD26 mRNA.

The induction of bacillus-Calmette-Guérin-activated killer cells requires the presence of monocytes and T-helper type-1 cells

Previously we have described the induction of MHC-unrestricted killer cells against bladder tumour cells by bacillus Calmette-Guérin (BCG), termed BCG-activated killer (BAK) cells. In the present paper we deal with the accessory-cell requirement for the activation of BAK cells. We show that monocytes are required for activating BAK cells, since no cytotoxicity can be induced in the absence of monocytes. Therefore, these phagocytes may represent the first step during the activation cascade of BAK cells. Furthermore, the presence of CD4+ T cells was essential for generating BAK cells: depleting peripheral blood mononuclear cells of CD4+ cells prior to stimulation with BCG abolished the cytotoxicity against bladder tumour cells. Experiments with monoclonal antibodies (mAb) neutralizing the activity of either interleukin-2 (IL-2) or interferon gamma (IFN gamma) underlined the importance of these cytokines: both mAb blocked the induction of BAK cells. Since both cytokines are related to the so-called Th1 pattern of T cells, we consider the second step of the generation of BAK cells as follows: monocytes presenting antigens of BCG trigger Th1-like cells in a preferred manner. These Th1-like T cells secrete IL-2 and IFN gamma and, thus, activate the BAK effector cells. Since CD4+ cells are dominant in the cells infiltrating the bladder wall after intravesical instillation of BCG in vivo, we postulate an important role for the Th1 subpopulation. We further postulate that the occurrence of macrophages in this infiltrate seems to be significant in the maintenance of the relapse-free state of the patient.

Prevention of venous thromboembolism in North America: results of a survey among general surgeons

PURPOSE

The purpose of this study was to analyze current attitudes toward the prevention of postoperative venous thromboembolism among North American general surgeons.

METHODS

A survey regarding awareness of the problem of venous thromboembolism and preferred modalities of prophylaxis was sent to 3500 randomly selected Fellows of the American College of Surgeons.

RESULTS

A total of 1018 (29.1%) surveys was returned. Most of the responding surgeons consider venous thromboembolism a serious health problem. Ninety percent of the surgeons use prophylaxis against venous thromboembolism routinely. The most frequently used modalities are intermittent pneumatic compression, low-dose heparin, and elastic stocking. A combination of physical and pharmacologic methods is used by one fourth of respondents, and only 50% start pharmacologic prophylaxis before the surgical procedure. The thrombosis risk factors that are most frequently considered by surgeons when deciding about using prophylaxis are history of venous thromboembolism, immobility, and length of operation.

CONCLUSIONS

North American surgeons who responded to this survey are well aware of the problem of venous thromboembolism and their approach to prevention has been significantly modified in the last 10 years. Compared with similar European surveys this survey reveals a higher implementations of physical methods such as intermittent pneumatic compression and elastic stockings. Because of the limited response rate and possibility of sampling bias, these findings should be interpreted with caution.

Endotoxin and lipid A stimulate proliferation of human T cells in the presence of autologous monocytes

In this paper we describe a new activity of LPS and partial structures: the induction of DNA synthesis and lymphokine production of human T lymphocytes. The LPS-induced T cell proliferation is dose dependent and requires 100 to 10,000 ng/ml of LPS or synthetic lipid A (compound 506) for optimal stimulation. In contrast, the synthetic lipid A precursor Ia (compound 406) is not active but rather antagonizes LPS-induced proliferation. The proliferation is accompanied by the expression of mRNA for the Th1 cell-derived lymphokines IFN-gamma and IL-2, but not for the Th2 lymphokines IL-4, IL-5, or IL-10. Highly enriched T lymphocyte preparations with less than 0.1% monocytes are not stimulated by LPS, showing that monocytes are required for T cell proliferation. Reconstitution experiments show that only monocytes, but not B lymphocytes, are able to support induction of DNA synthesis. Separating LPS-stimulated monocytes from T lymphocytes by a membrane, permeable for cytokines but not for cells, abolishes T cell proliferation. Fixation of monocytes with paraformaldehyde also abrogates their accessory function for T cells. If the monocytes are preincubated for 2 h at 37 degrees C with LPS and then washed, they still are able to induce T cell proliferation in the absence of additional LPS. Our results indicate that human T cells respond in a monocyte-supported manner to LPS exposure by proliferation and lymphokine production. We hypothesize that this reactivity of T lymphocytes to LPS may be of clinical relevance.

Endotoxin and lipid A stimulate proliferation of human T cells in the presence of autologous monocytes

In this paper we describe a new activity of LPS and partial structures: the induction of DNA synthesis and lymphokine production of human T lymphocytes. The LPS-induced T cell proliferation is dose dependent and requires 100 to 10,000 ng/ml of LPS or synthetic lipid A (compound 506) for optimal stimulation. In contrast, the synthetic lipid A precursor Ia (compound 406) is not active but rather antagonizes LPS-induced proliferation. The proliferation is accompanied by the expression of mRNA for the Th1 cell-derived lymphokines IFN-gamma and IL-2, but not for the Th2 lymphokines IL-4, IL-5, or IL-10. Highly enriched T lymphocyte preparations with less than 0.1% monocytes are not stimulated by LPS, showing that monocytes are required for T cell proliferation. Reconstitution experiments show that only monocytes, but not B lymphocytes, are able to support induction of DNA synthesis. Separating LPS-stimulated monocytes from T lymphocytes by a membrane, permeable for cytokines but not for cells, abolishes T cell proliferation. Fixation of monocytes with paraformaldehyde also abrogates their accessory function for T cells. If the monocytes are preincubated for 2 h at 37 degrees C with LPS and then washed, they still are able to induce T cell proliferation in the absence of additional LPS. Our results indicate that human T cells respond in a monocyte-supported manner to LPS exposure by proliferation and lymphokine production. We hypothesize that this reactivity of T lymphocytes to LPS may be of clinical relevance.

On the mode of action of intravesical bacillus Calmette-Guérin: in vitro characterization of BCG-activated killer cells

Previously we had shown that, upon activation with viable bacillus Calmette-Guérin (BCG), peripheral blood mononuclear cells (PBMNC) could be rendered cytotoxic against otherwise insensitive natural killer (NK)-resistant bladder cancer cell lines. This phenomenon had been termed the BCG-activated killer (BAK) cell phenomenon. By means of depletion and enrichment procedures of mononuclear cell subpopulations derived from BCG-activated PBMNC we further characterized the cytolytic BAK effector cells functionally in an in vitro cytotoxicity assay against the bladder carcinoma cell line BT-A and phenotypically in their pathway of activation. Neither macrophages nor CD4+ T-helper/inducer cells exerted cytotoxic BAK activity. This cytotoxicity was restricted to the CD8+CD56+ subpopulation of T-cytotoxic/NK cells. Furthermore, activation of BAK cells via interferon gamma (IFN-gamma) was evidenced by the complete inhibition of BAK cell generation with an IFN-gamma antibody.

Dipeptidyl peptidase IV (CD26) on human lymphocytes. Synthetic inhibitors of and antibodies against dipeptidyl peptidase IV suppress the proliferation of pokeweed mitogen-stimulated peripheral blood mononuclear cells, and IL-2 and IL-6 production

In the present report, we describe that synthetic inhibitors of and polyclonal and monoclonal antibodies against the membrane ectoenzyme dipeptidyl peptidase IV (DP IV, CD26) inhibit the production of IL-2 and IL-6 and, concomitantly, DNA synthesis of pokeweed mitogen-stimulated peripheral blood mononuclear cells (PBMC). The release of IL-1 and TNF-alpha, was not influenced under these conditions. The data support the hypothesis that DP IV, possibly in conjunction with other peptidase, is involved in the regulation of activation and proliferation of T lymphocytes.

Induction of bacillus-Calmette-Guérin-activated killer cells from human peripheral blood mononuclear cells against human bladder carcinoma cell lines in vitro

Cytotoxicity against two human bladder carcinoma cell lines (BT-A and BT-B) was investigated using human peripheral blood mononuclear cells (PBMC) stimulated with viable bacillus Calmette-Guérin (BCG) or sonicated BCG (s-BCG). We applied a cytotoxicity assay based on radioactive labelling of tumour cells by incorporation of L[3H]methionine. The results were compared with the cytotoxicity exerted by lymphokine-activated killer (LAK) cells generated by interleukin-2 (IL-2) and interferon gamma (IFN gamma). BCG-stimulated PBMC showed a cytotoxic potential against BT-A and BT-B comparable to that of IFN gamma-generated LAK cells, but this did not reach the level of IL-2-generated LAK cells. We termed these cytotoxic effectors BCG-activated killer (BAK) cells. In contrast to their cytotoxicity against bladder tumour cells, BAK cells did not differ from unstimulated PBMC in the killing of K562 cells. Only viable but not sonicated BCG was able to induce cytotoxicity against BT-A and BT-B. We could demonstrate the presence of the cytokines IFN gamma, IL-2, tumour necrosis factor alpha (TNF alpha) and TNF beta in the supernatants harvested during the generation of BAK cells. Monoclonal antibodies neutralizing IFN gamma were able to inhibit BCG-mediated cytotoxicity, giving evidence of the involvement of IFN gamma in the induction of BAK cells. Furthermore, we performed experiments to investigate the cytotoxic potential of distinct cell populations. The cells effective in BCG-activated killing of bladder tumour cells could be localized within the CD8+/CD56+ lymphocyte subset. CD4+ cells and macrophages did not exhibit cytolytic activity. Our findings imply that the activation by BCG of CD8+/CD56+ killer cells might be an important antitumoral mechanism during BCG therapy against superficial urothelial bladder cancer.

Anti-CD26 monoclonal antibodies can reversibly arrest human T lymphocytes in the late G1 phase of the cell cycle

Three different anti-CD26 monoclonal antibodies (mAbs) are described, which specifically inhibited proliferation of human T lymphocytes after stimulation with PHA, tetanus toxoid or soluble anti-CD3 mAb. Anti-CD26 mAbs induced in T cells a dose-dependent shift of the maximum of DNA synthesis, which was due to a transitory arrest of cells in the cell cycle. This cell cycle arrest was found to occur in the late phase of G1 since the expression of the T cell activation markers CD25-, CD71-, and HLA-DR-positive cells was the same in anti-CD26 mAb-containing and control cultures. Propidium iodide staining further confirmed the assumption that the arrest occurs in the first round of the cell cycle before S phase cells were detectable. Because the cells were arrested before consuming IL-2 in the S phase, we observed in accumulation of IL-2 in anti-CD26 mAb-containing cultures, whereas IFN-gamma production by PHA-activated T lymphocytes was reduced. These data indicate that CD26 is involved in the processes of T cell activation and proliferation.

Expression of CD26 (dipeptidyl peptidase IV) on memory and naive T lymphocytes

It has been suggested that human CD26-positive T lymphocytes represent the memory pool of the cellular immune system. For proof of this suggestion we analysed the responsiveness of CD26-positive and CD26-negative T lymphocytes after antigenic stimulation in limiting dilution experiments. After stimulation with tetanus toxoid (TT) the number of proliferating cells within the CD26-positive subset was two- to sixfold higher than that within the CD26-negative subset. These differences in responsiveness were also detectable between CD4+/CD26+ and CD4+/CD26- T cells. To further investigate the memory character of the cells, human peripheral blood mononuclear cells were stimulated with TT for 7 or 14 days. Thereafter, CD26+ and CD26- T cells were isolated and restimulated with TT in limiting dilution experiments. Responding cells were found not only within the CD26-positive subset but also within the CD26-negative subset, and their number increased with time. Surface marker analysis of freshly isolated human T lymphocytes or T-cell clones indicated that CD26 is not a stable cell surface marker. Furthermore, CD26 is both absent and present on CD29-positive or CD45RA-positive cells, indicating no association of CD26 with surface markers for memory or naive T cells, respectively. These results strongly argue against the hypothesis that CD26-positive T cells represent the memory pool. We conclude that CD26 is an activation marker of T lymphocytes, which is associated with reactivity on naive and memory cells.

Expression of CD26 (dipeptidyl peptidase IV) on resting and activated human T-lymphocytes

CD26 is an activation antigen which is expressed on the surface of human T-lymphocytes. It has been characterized to be the dipeptidyl peptidase IV (DPP IV). Considerable amounts of CD26 are already present on resting T-lymphocytes. The expression of CD26 is enhanced by T-cell mitogens or antigens. A correlation of CD26 expression and of enhanced enzymatic activity was observed after T-cell activation. Our data indicate that not only the immunoreactivity, but also the enzymatic activity of CD26 are detectable on the cell surface. In addition, de novo expression of CD26 was demonstrated on CD26-negative T-cells after mitogenic or antigenic stimulation. CD26 expression is initiated during the G1 phase of the cell cycle. The expression occurs nearly simultaneously with HLA-DR, but later than CD25. Similar to CD25 and HLA-DR, CD26 is not a permanent marker on the surface of T-lymphocytes, but is down-regulated after 7 days of culture. When testing the influence of interleukin 1, interleukin 2, tumour necrosis factor, and interferon-gamma on the expression of CD26, no effect was found on unstimulated or on mitogen-stimulated T-lymphocytes. The binding of two different monoclonal antibodies against CD26 (anti-DPP IV and anti-Tal) to resting and activated T-lymphocytes revealed a different pattern of immunoreactivity. Resting T-lymphocytes reacted stronger with anti-DPP IV than with anti-Tal. However, binding of the two monoclonal antibodies to T-cell blasts did not show significant differences. These data indicate that CD26 may be expressed in differently modulated configurations on the surface of T-cells, which may be associated with a distinct status of activation and/or function.

CD26 antigen is a surface dipeptidyl peptidase IV (DPPIV) as characterized by monoclonal antibodies clone TII-19-4-7 and 4EL1C7

In this study we investigated the binding of three different monoclonal antibodies (MoAb), TII 19-4-7, 4EL1C7, and B1.19.2, which are clustered in CD26 to the ectoenzyme dipeptidyl peptidase IV (DPP IV) and to T lymphocytes. We found that all three MoAb bind to both unstimulated and mitogen-stimulated T lymphocytes. Further results indicated an inconsistency within the CD26-clustered MoAb: TII 19-4-7 and 4EL1C7, but not B1.19.2, recognized DPP IV on the surface o T lymphocytes and immobilized on solid-phase ELISA or Western blot. There was competition of binding to DPP IV between TII 19-4-7 and 4EL1C7. From these results we conclude that CD26 antigen is represented by the ectoenzyme DPP IV. TII 19-4-7 and 4EL1C7 recognize the same or partly identical epitopes on DPP IV, whereas B1.19.2 recognizes a different antigen. TII 19-4-7 and 4EL1C7, but not B1.19.2, should be clustered in CD26.

Dipeptidyl peptidase IV in human T lymphocytes. Impaired induction of interleukin 2 and gamma interferon due to specific inhibition of dipeptidyl peptidase IV

Specific inhibitors of the membrane-bound dipeptidyl peptidase IV (DP IV) and polyclonal antibodies against this enzyme were used to investigate the relationships between DP IV activity and the production and action of T cell-derived lymphokines. Production of interleukin 2 (IL-2) and gamma interferon by mitogen plus phorbol ester-stimulated mononuclear cells from human blood was found to be reduced in the presence of N-Ala-Pro-O-(nitrobenzoyl-)-hydroxylamine, epsilon-(4'-nitro) benzoxycarbonyl-Lys-Pro, and anti-(DP IV) immunoglobulin in a dose-dependent manner. Moreover, the proliferative response of mitogen-stimulated mononuclear cells to IL-2 is impaired in the presence of DP IV inhibitors. Therefore it is suggested that the membrane peptidase DP IV is involved in the induction and activation of cytokines controlling lymphocyte proliferation.