Sea water acclimation of rainbow trout (Oncorhynchus mykiss) modulates the mucosal transcript immune response induced by Vibrio anguillarum and Aeromonas salmonicida vaccine, and prevents further transcription of stress-immune genes in response to acute stress.

Mucosal tissues appear to be more important in fish than in mammals due to living in a microbial-rich aquatic milieu, yet the complex interaction between the immune and the neuroendocrine system in these tissues remains elusive. The aim of this work was to investigate the mucosal immune response in immunized rainbow trout vaccinated with Alpha ject vaccine (bivalent), kept in fresh water (FW) or transferred to seawater (SW), and to evaluate their response to acute stress (chasing). Acute stress resulted in higher levels of plasma cortisol (Sham + Stress and Vaccine + Stress). A similar response was observed in skin mucus, but it was lower in Vaccine + Stress compared with stressed fish. With a few exceptions, minimal alterations were detected in the transcriptomic profile of stress-immune gene in the skin of vaccinated and stressed fish in both FW and SW. In the gills, the stress elicited activation of key stress-immune components (gr1, mr, ß-ar, hsp70, c3, lysozyme, α-enolase, nadph oxidase, il1ß, il6, tnfα, il10 and tgfß1) in FW, but fewer immune changes were induced by the vaccine (nadph oxidase, il6, tnfα, il10 and igt) in both SW and FW. In the intestine, an array of immune genes was activated by the vaccine particularly those related with B cells (igm, igt) and T cells (cd8α) in FW with no stimulation observed in SW. Therefore, our survey on the transcriptomic mucosal response demonstrates that the immune protection conferred by the vaccine to the intestine is modulated in SW. Overall, our results showed: i) plasma and skin mucus cortisol showed no additional stress effect induced by prolonged SW acclimation, ii) the stress and immune response were different among mucosal tissues which indicates a tissue-specific response to specific antigens/stressor. Further, the results suggest that the systemic immune organs may be more implicated in infectious events in SW (as few changes were observed in the mucosal barriers of immunized fish in SW) than in FW.

Decrease in preferred temperature in response to an immune challenge in lizards from cold environments in Patagonia, Argentina.

In ectotherms, the likelihood of surviving an infection is determined by the efficiency of thermoregulation, the availability of a variety of thermal microenvironments, the individual's health status, and the virulence of the infective agent. Physiological and behavioral demands related to an efficient immune response entail a series of costs that compete with other vital activities, specifically energy storage, growth, reproduction, and maintenance functions. Here, we characterize the thermal biology and health status by the presence of injuries, ectoparasites, body condition, and individual immune response capacity (using phytohemagglutinin in a skin-swelling assay) of the southernmost lizards of the world, Liolaemus sarmientoi, endemic to a sub-optimal, cold environment in Patagonia, Argentina. In particular, we study the effect of a bacterial endotoxin (lipopolysaccharide; LPS-treatment) on thermoregulation. We found that the field-active body temperature (Tb) was much lower than the preferred body temperature (Tp) obtained in the laboratory. All the individuals were in good body condition at the beginning of the experiments. The phytohemagglutinin test caused detectable thickening in sole-pads at 2 h and 24 h post-assay in males and non-pregnant females, indicating a significant innate immune response. In the experimental immune challenge, the individuals tended to prefer a low body temperature after LPS-treatment (2 h post-injection) and developed hypothermia, while the control individuals injected with phosphate buffered saline (PBS), maintained their body temperature throughout the trial. In both the LPS-treatment and PBS-control individuals, BC declined during the experiment. Hypothermia may allow this southernmost species to optimize the use of their energetic resources and reduce the costs of thermoregulation in a cold-temperate environment where they rarely attain the mean Tp (35.16 °C) obtained in laboratory.

Acclimation to cold and warm temperatures is associated with differential expression of male carp blood proteins involved in acute phase and stress responses, and lipid metabolism.

The environmental temperature affects plasma biochemical indicators, antioxidant status and hematological and immunological parameters in fish. So far, only single blood proteins have been identified in response to temperature changes. The aim of this study was to compare the proteome of carp blood plasma from males acclimated to warm (30 °C) and cold (10 °C) temperatures by two-dimensional differential gel electrophoresis followed by MALDI-TOF/TOF mass spectrometry. A total of 47 spots were found to be differentially regulated by temperature (>1.2-fold change, p < 0.05): 25 protein spots were more abundant in warm-acclimated males and 22 were enriched in cold-acclimated males. The majority of differentially regulated proteins were associated with acute phase response signalling involved in: i) activation of the complement system (complement C3-H1), ii) neutralization of proteolytic enzymes (inter-alpha inhibitor H3, fetuin, serpinA1, antithrombin, alpha2-macroglobulin), iii) scavenging of free hemoglobin and radicals (haptoglobin, Wap65 kDa), iv) clot-formation (fibrinogen beta and alpha chain, T-kininogen) and v) the host's immune response modulation (ApoA1 and ApoA2). However, quite different sets of these proteins or proteoforms were involved in response to cold and warm temperatures. In addition, cold acclimation seems to be related to the proteins involved in lipid metabolism (apolipoproteins A and 14 kDa) and stress response (corticosteroid binding globulin). We discovered a strongly regulated protein Cap31 upon cold acclimation, which can serve as a potential blood biomarker of cold response in carp. These studies significantly extend our knowledge concerning mechanisms underlying thermal adaptation in poikilotherms.

Short-term heat acclimation prior to a multi-day desert ultra-marathon improves physiological and psychological responses without compromising immune status.

Multistage, ultra-endurance events in hot, humid conditions necessitate thermal adaptation, often achieved through short term heat acclimation (STHA), to improve performance by reducing thermoregulatory strain and perceptions of heat stress. This study investigated the physiological, perceptual and immunological responses to STHA prior to the Marathon des Sables. Eight athletes (age 42 ± 4 years and body mass 81.9 ± 15.0 kg) completed 4 days of controlled hyperthermia STHA (60 min·day‒1, 45°C and 30% relative humidity). Pre, during and post sessions, physiological and perceptual measures were recorded. Immunological measures were recorded pre-post sessions 1 and 4. STHA improved thermal comfort (P = 0.02), sensation (P = 0.03) and perceived exertion (P = 0.04). A dissociated relationship between perceptual fatigue and Tre was evident after STHA, with reductions in perceived Physical (P = 0.04) and General (P = 0.04) fatigue. Exercising Tre and HR did not change (P > 0.05) however, sweat rate increased 14% (P = 0.02). No changes were found in white blood cell counts or content (P > 0.05). Four days of STHA facilitates effective perceptual adaptations, without compromising immune status prior to an ultra-endurance race in heat stress. A greater physiological strain is required to confer optimal physiological adaptations.

Post-capture immune gene expression studies in the deep-sea hydrothermal vent mussel Bathymodiolus azoricus acclimatized to atmospheric pressure.

Deep-sea hydrothermal vents are extreme habitats that are distributed worldwide in association with volcanic and tectonic events, resulting thus in the establishment of particular environmental conditions, in which high pressure, steep temperature gradients, and potentially toxic concentrations of sulfur, methane and heavy metals constitute driving factors for the foundation of chemosynthetic-based ecosystems. Of all the different macroorganisms found at deep-sea hydrothermal vents, the mussel Bathymodiolus azoricus is the most abundant species inhabiting the vent ecosystems from the Mid-Atlantic Ridge (MAR). In the present study, the effect of long term acclimatization at atmospheric pressure on host-symbiotic associations were studied in light of the ensuing physiological adaptations from which the immune and endosymbiont gene expressions were concomitantly quantified by means of real-time PCR. The expression of immune genes at 0 h, 12 h, 24 h, 36 h, 48 h, 72 h, 1 week and 3 weeks post-capture acclimatization was investigated and their profiles compared across the samples tested. The gene signal distribution for host immune and bacterial genes followed phasic changes in gene expression at 24 h, 1 week and 3 weeks acclimatization when compared to other time points tested during this temporal expression study. Analyses of the bacterial gene expression also suggested that both bacterial density and activity could contribute to shaping the intricate association between endosymbionts and host immune genes whose expression patterns seem to be concomitant at 1 week acclimatization. Fluorescence in situ hybridization was used to assess the distribution and prevalence of endosymbiont bacteria within gill tissues confirming the gradual loss of sulfur-oxidizing (SOX) and methane-oxidizing (MOX) bacteria during acclimatization. The present study addresses the deep-sea vent mussel B. azoricus as a model organism to study how acclimatization in aquaria and the prevalence of symbiotic bacteria are driving the expression of host immune genes. Tight associations, unseen thus far, suggest that host immune and bacterial gene expression patterns reflect distinct physiological responses over the course of acclimatization under aquarium conditions.

Thermal acclimation in the perch (Perca fluviatilis L.) immunity.

Fish immune systems must be able to cope with pathogens over a wide temperature range. Earlier research suggest that fish are more dependent on innate immune responses based on pattern recognition than acquired functions with specific recognition. If this applies to phagocytes, then opsonins (serum factors that augment phagocytosis e.g. immunoglobulins and complement proteins) attached on zymosan (Z) particles should be recognized better at higher temperatures than Z only. Z is recognized by glucan receptor representing pattern recognition. In this study perch were acclimated to 5 °C or 16 °C for 3-5 weeks. The recognition and activation of respiratory burst reaction of peripheral blood phagocytes was examined at seven different measurement temperatures (5, 10, 16, 20, 24 27, and 30 °C) when the cells were stimulated with Z and serum opsonized zymosan (OZ). Respiratory burst was measured as luminol chemiluminescence (CL) from diluted whole blood. OZ-induced CL per volume of blood was on average approximately 4.6 times higher in 16 °C acclimated fish than 5 °C acclimated perch (P<0.0001). Z-induced CL was approximately 3 times higher at lower temperatures in 16 °C acclimated perch than 5 °C acclimated fish and 6-9 times higher at 27 °C and 30 °C (P<0.001), respectively. CL reaction kinetics were faster in perch acclimated to 5 °C than 16 °C -acclimated fish, especially at low temperatures (P<0.001). Thermal acclimation caused a 3-4 °C shift in temperature response curves of CL towards the acclimation temperature (P<0.0001 and P<0.053 in Z and OZ-induced CL, respectively). Serum opsonins activated perch phagocytes substantially better at higher temperatures in both acclimation groups, which is consistent with an earlier study in rainbow trout (O. mykiss). However, opsonin recognition was significantly better in 16 °C acclimated perch than 5 °C acclimated fish, which was seen as higher CLs for OZ compared to Z, especially at higher temperatures. This is opposite to previously reported results in rainbow trout. Differences between rainbow trout and perch in opsonin recognition by blood phagocytes suggest that the living habits of perch, which prefers approximately a 10 °C higher temperature than rainbow trout, may be reflected in immune cell functions. Results of the present examination suggest that also in fish phagocytes pattern recognition is the prevailing system at low temperatures, and specific recognition is more effective at high temperatures.

Investigation of immunoglobulins in skin of the Antarctic teleost Trematomus bernacchii.

The presence and production of IgM in the skin of the Antarctic teleost Trematomus bernacchii were investigated in this study. Immunoglobulins purified from cutaneous mucus and analysed by SDS-PAGE run under non-reducing and reducing conditions, were composed of heavy and light chains of 78 kDa and 25 kDa respectively, with a relative molecular mass of 830 kDa indicating that mucus IgM are tetramers as the serum IgM. Mature transcripts encoding the constant domains of both the secretory and membrane-bound Igµ chain were seen in T. bernacchii skin using a PCR strategy and the expression of the secretory Igµ chain in the skin was compared with that in other tissues by Real-time PCR. Cytological investigations revealed the presence of either immunoglobulins or their transcripts in occasional lymphocytes distributed close to the basal membrane. IgM once produced here, enters the filament-containing cells and is released into the mucus when these cells degenerate and detach from the epidermis. Our findings indicate that a cutaneous defence mechanism, functioning as anatomical and physiological barrier under subzero conditions, is present in this Antarctic species as an important component of the immune system.

The effects of elevated temperature on the sexual traits, immunology and survivorship of a tropical ectotherm.

In 2007, the Intergovernmental Panel on Climate Change projected an average global air temperature increase of 1.1-6.4°C by the end of the 21st century. Although the tropics are predicted to experience less extreme temperature increases than regions of higher latitude, tropical ectotherms live close to their thermal limits, and are thus particularly vulnerable to increases in temperature. In this study, we examined how predicted patterns of global warming will affect survival and sexual traits in the Trinidadian guppy (Poecilia reticulata). Guppies were exposed from birth to one of four temperature treatments: 23, 25 (control), 28 or 30°C. We measured brood survival and, at sexual maturity, male ornamentation, sperm traits and immune response. Our results show that increases in temperature result in guppies that have shorter, slower sperm but that there is an optimum temperature for ornamental hue at 28°C. Given the importance of sperm quality for reproduction, these results suggest population viability could be affected by warming. However, we found no difference in brood survival or immune response to a novel antigen across the treatments, indicating that survival may not be as vulnerable as previously thought. Overall, our data suggest that male sexual traits, and in particular sperm performance, are more sensitive than survival to a warming environment.

Effects of naproxen on the hypobaric hypoxia-induced immune changes in male rats.

Some cell-mediated immune responses are altered in hypobaric hypoxic (HH) condition in rats. Prostaglandins (PGs) are increased in hypobaric hypoxia and non-steroidal anti-inflammatory drugs are used to facilitate acclimatization in high altitude by inhibiting PGs. The present study explores the role of PGs in hypobaric hypoxia-induced immune responses by inhibiting its synthesis with different doses of naproxen. The rats were exposed to HH condition at 18,000 ft in a simulated chamber for 8 h/day for 6 days. The phagocytic activity of circulating blood WBC, measured by fluorescein isothiocyanate-tagged bacterial cell, was increased in HH and this change was blocked after administration of naproxen. There was reduction of natural killer cell cytotoxicity of splenic mononuclear cell and delayed type of hypersensitivity responses to bovine serum albumin in rats exposed to HH condition but these immune responses were blocked after administration of naproxen in HH condition. The leukocytes adhesive inhibition index was not altered in HH condition and after administration of naproxen in HH condition. The serum corticosterone (CORT) concentration was increased in rats exposed to HH condition and this elevated CORT concentration was blocked after administration of naproxen in HH condition. The observed HH-induced immune changes are inhibited by naproxen in a dose-dependent manner. The study indicates that hypobaric hypoxia-induced immune changes are mediated by PGs.

Functional and metabolic characterization of hemocytes of the green mussel, Perna viridis: in vitro impacts of temperature.

The green mussel, Perna viridis, is a bivalve mollusk native to Asia and was recently introduced to Florida, USA. Since its first observation in 1999 in Tampa Bay, Florida, green mussel population has expanded considerably, to reach the Atlantic coast of Florida, Georgia and South Carolina. Most of currently available studies about the ecology and biology of green mussels were performed in the Indian and Pacific oceans. Very recently, it has been suggested that due to a weak low temperature resistance, green mussels might have already reached the Northern edge of their distribution in the USA. However, there is currently an obvious lack of data about the adaptation capacities of Perna viridis to environmental conditions in Florida, especially at the physiological and cellular levels. In the present work, we determined and characterized the populations of circulating hemocytes, and the cellular components of hemolymph involved in various physiological functions, including immunity. Two main populations were characterized, hyalinocytes and granulocytes. Granulocytes accounted for 60% of circulating cells, and displayed higher phagocytic capacities, lysosomal content and basal oxidative metabolism than hyalinocytes. Hemocyte parameters were not influenced by the size of green mussels. In addition, hemocytes were subjected to acute temperature challenges (10, 20 and 30 °C) and their immune-related functions and metabolism analyzed. Our results showed that 10 °C represent a stressful condition for the Floridian green mussels, as depicted by a low phagocytosis capacity and an increase of oxidative metabolism.

Effects of relocation on immunological and physiological measures in female squirrel monkeys (Saimiri boliviensis boliviensis).

In the present study, we have quantified the effects of transport, relocation and acclimate/adapt to their new surroundings on female squirrel monkey. These responses are measured in blood samples obtained from squirrel monkeys, at different time points relative to their relocation from their old home to their new home. A group of squirrel monkeys we transported, by truck, for approximately 10 hours. Peripheral blood mononuclear cells (PBMCs) were assayed in order to evaluate the phenotype of lymphocyte subsets by flow, mitogen-specific immune responses of PBMCs in vitro, and levels of cytokines at various time points including immediately before transport, immediately upon arrival, and after approximately 150 days of acclimation. We observed significant changes in T cells and subsets, NK and B cells (CD4+, CD8+, CD4+/CD8+, CD16+, and CD20+). Mitogen specific (e.g. PHA, PWM and LPS) proliferation responses, IFN-γ by ELISPOT assay, and cytokines (IL-2, IL-4 and VEGF) significant changes were observed. Changes seen in the serum chemistry measurements mostly complement those seen in the hematology data. The specific goal was to empirically assess the effects of relocation stress in squirrel monkeys in terms of changes in the numbers and functions of various leukocyte subsets in the blood and the amount of time required for acclimating to their new environment. Such data will help to determine when newly arrived animals become available for use in research studies.

Zebrafish fin immune responses during high mortality infections with viral haemorrhagic septicemia rhabdovirus. A proteomic and transcriptomic approach.

BACKGROUND: Despite rhabdoviral infections being one of the best known fish diseases, the gene expression changes induced at the surface tissues after the natural route of infection (infection-by-immersion) have not been described yet. This work describes the differential infected versus non-infected expression of proteins and immune-related transcripts in fins and organs of zebrafish Danio rerio shortly after infection-by-immersion with viral haemorrhagic septicemia virus (VHSV). RESULTS: Two-dimensional differential gel electrophoresis detected variations on the protein levels of the enzymes of the glycolytic pathway and cytoskeleton components but it detected very few immune-related proteins. Differential expression of immune-related gene transcripts estimated by quantitative polymerase chain reaction arrays and hybridization to oligo microarrays showed that while more transcripts increased in fins than in organs (spleen, head kidney and liver), more transcripts decreased in organs than in fins. Increased differential transcript levels in fins detected by both arrays corresponded to previously described infection-related genes such as complement components (c3b, c8 and c9) or class I histocompatibility antigens (mhc1) and to newly described genes such as secreted immunoglobulin domain (sid4), macrophage stimulating factor (mst1) and a cluster differentiation antigen (cd36). CONCLUSIONS: The genes described would contribute to the knowledge of the earliest molecular events occurring in the fish surfaces at the beginning of natural rhabdoviral infections and/or might be new candidates to be tested as adjuvants for fish vaccines.

Rapid thermal immune acclimation in common musk turtles (Sternotherus odoratus).

As infectious diseases in ectothermic vertebrates increasingly threaten wild populations, understanding how host immune systems are affected by the environment is key to understanding the process of infection. In this study, we investigated how temperature change and simulated bacterial infection (via lipopolysaccharide [LPS] injection) interacted to regulate innate immunity, as measured by bactericidal ability (BA), phagocytosis rate, and heterophil:lymphocyte ratio (HLR) in common musk turtles (Sternotherus odoratus). We found that LPS stimulated an acute immune response, as measured by an increase in BA, phagocytosis rate, and HLR. When exposed to a 5 or 10°C temperature change for 48 hr, turtles rapidly acclimated to the new temperature by adjusting their immune output. This acclimation was compensatory as seen by elevated rates of immune output in colder animals and decreased rates of immune output in warmer animals. These results indicate that while temperature change may be a constraint on some animals, S. odoratus have the ability to rapidly adjust immunity to match environmental thermal demand. This rapid ability to adjust immunity may be related to the broad geographic distribution of musk turtles. Future research should focus on how immune acclimation in ectotherms varies both intraspecifically and interspecifically across regional scales and geographic distributions.

Effect of suboptimal temperature on the regulation of endogenous antigen presentation in a rainbow trout hypodermal fibroblast cell line.

Rainbow trout (Oncorhynchus mykiss) face low environmental temperatures over winter months and during extreme low temperature events. Suboptimal temperatures are known to negatively impact the teleost immune system, although there is mixed evidence in rainbow trout as to the effect on the endogenous antigen processing and presentation pathway (EAPP). The EAPP is an important pathway for antiviral defense that involves the presentation of endogenous peptides on the cell surface for recognition by cytotoxic T cells. Using a rainbow trout hypodermal fibroblast (RTHDF) cell line as an in vitro model, we determined that constitutive EAPP transcript levels are not impaired at low temperature, but induction of up-regulation of these transcripts is delayed at the suboptimal temperature following exposure to poly(I:C) or viral haemorrhagic septicaemia virus IVb, which was still able to enter and replicate in the cell line at 4 °C, albeit with reduced efficiency. The delay in the induction of EAPP mRNA level up-regulation following poly(I:C) stimulation coincided with a delay in ifn1 transcript levels and secretion, which is important since interferon-stimulated response elements were identified in the promoter regions of the EAPP-specific members of the pathway, implying that IFN1 is involved in the regulation of these genes. Our results suggest that the ability of rainbow trout to mount an effective immune response to viral pathogens may be lessened at suboptimal temperatures.

Lag of Immunity Across Seasonal Acclimation States in Gopher Tortoises (Gopherus Polyphemus).

Disease outbreaks are of increasing importance to ectothermic vertebrates as one of numerous results of global change. Anthropogenic climate change is predicted to increase climatic instability, thereby altering natural thermal environments. In this study, we evaluated the direct effects of rapid temperature change on immunity in Gopher Tortoises (Gopherus polyphemus). Specifically, we tested the lag hypothesis, which predicts significant misalignment of optimal and realized immunity when temperature rapidly changes. We assayed constitutive innate immunity, B-cell humoral responses, and heterophil: lymphocyte ratios in response to rapid temperature changes corresponding to realistic changes in body temperature between winter and summer. We found that during summer, rapid temperature reduction caused a series of changes in immunity, including reduced bactericidal ability (P = 0.002), reduced humoral response (P < 0.0001), and increased heterophil:lymphocyte ratios (P < 0.0001). During winter, we found that a temperature increase provided no benefit to immunity. Specifically, there was no increase in bactericidal ability as was predicted by the lag hypothesis. In winter, humoral responses were significantly reduced as a result of rapid warming (P = 0.011) and the rapid warming caused a significant reduction in heterophil:lymphocyte ratios (P < 0.0001). Independent of temperature, we found a significant acclimation effect of winter relative to summer conditions in humoral response (P < 0.001), which showed an overall increase in this parameter during winter. Our findings demonstrate that rapid temperature change, regardless of its direction, is a constraint on immunity in ectothermic vertebrates.

Seasonal Acclimation of Constitutive Immunity in Gopher Tortoises Gopherus polyphemus.

Studies have suggested a role for natural seasonal change to drive patterns of disease, especially within ectothermic vertebrates. In light of recent climate change, it is important to understand baseline disease resistance in a seasonal context to further understand the role that changes in seasonal weather patterns may have in increasing disease frequency. Herein we found support for the seasonal acclimation hypothesis in Gopherus polyphemus (gopher tortoise), which indicated that natural seasonal variation causes differences in baseline immune function across seasonal acclimation states. We found that an innate immune parameter, bactericidal ability (BA), was significantly elevated in the summer (P < 0.00001). Circulating leukocyte profiles varied significantly among seasons, with heterophils and monocytes increased (P = 0.00019 and P = 0.0001, respectively) and lymphocytes decreased (P < 0.00001) during winter. We assayed baseline glucocorticoid concentration (e.g., corticosterone [CORT]) across seasons and sampling conditions to test whether CORT drove the seasonal pattern in immunological acclimation. CORT was significantly lowest during winter and in animals temporarily maintained in seminatural conditions. These changes in CORT occurred independently of the immunological adjustments, suggesting that the seasonal pattern of immunity was not mediated by CORT secretion. The reduction in lymphocytes and BA and also BA during winter suggest that seasonal acclimation is likely a restraint on energetic output when temperature is low and physiological performance is thermally constrained. While these parameters were reduced in winter, the increase in heterophils and monocytes may indicate a compensatory immune adjustment to increase the number of innate phagocytic cells.

Effect of temperature on macrophage activation and the production of macrophage activating factor by rainbow trout (Oncorhynchus mykiss) leucocytes.

Production of macrophage activating factor (MAF) by rainbow trout leucocytes has been shown to be temperature dependent in vivo and in vitro. Cells from fish held at 14 degrees C and stimulated to produce MAF immediately after isolation were capable of secreting MAF down to 6 degrees C (the lowest temperature tested). However, after 48 h at 6 degrees C, these leucocytes show impaired MAF secretion. Acclimation of fish to low temperatures (7 degrees C) did not recover the inhibitory effects of low in vitro temperatures on MAF production, but if these leucocytes were preincubated at 10 or 18 degrees C for 48 h, MAF was produced from these cells. Interestingly, macrophages isolated from fish kept at 7 or 14 degrees C and cultured at low temperatures (6 degrees C) were responsive to MAF-containing supernatants, and showed a higher relative increase in respiratory burst activity compared with their counterparts cultured at 10 and 18 degrees C. Such observations clearly demonstrate that a major impairment of bactericidal activity at low temperatures resides within the specific immune compartment of fish. The implications for fish health are discussed.

Relationship between cold tolerance and generation of suppressor macrophages during acute cold stress.

Acute cold stress induces suppressor macrophages expressing large numbers of receptors to the crystallizable fragment (Fc) portion of immunoglobulin G (MAC-1+ FcgammaRII/IIIbright cells), resulting in the immunosuppression of splenocyte mitogenesis. The generation of MAC-1+ FcgammaRII/IIIbright cells is mediated by the action of glucocorticoids (GCs) through the GC-receptor. In the present study, the generation of MAC-1+ FcgammaRII/IIIbright cells in peritoneal exudate cells was closely related to the decrease of rectal temperature during 3-day exposure to 5 degrees C. We next investigated the effects of improved cold tolerance on the generation of MAC-1+ FcgammaRII/IIIbright cells during acute cold stress. Mice were adapted to cold by exposure to 5 degrees C for 3 wk (cold-acclimated mice) and then reexposed to 5 degrees C for 3 h (acute cold stress) after living at 25 degrees C for 24 h. The rectal temperature of cold-acclimated mice was not decreased by the acute cold stress. In addition, the proportion of MAC-1+ FcgammaRII/IIIbright cells in peritoneal exudate cell population from cold-acclimated mice was unaffected by the acute cold stress. The cold acclimation significantly attenuated the increases in serum corticosterone levels and the expression of the GC-receptor mRNA on peritoneal exudate cells in response to acute cold stress. These results suggest that the altered GC response to acute cold stress by the improvement of cold tolerance inhibits the generation of suppressor macrophages during acute cold stress.

Role of melatonin in mediating seasonal energetic and immunologic adaptations.

Winter is energetically demanding and stressful; thermoregulatory demands increase when food availability usually decreases. Physiological and behavioral adaptations, including termination of breeding, have evolved among nontropical animals to cope with the energy shortages during winter. Presumably, selection for the mechanisms that permit physiological and behavioral anticipation of seasonal ambient changes have led to current seasonal breeding patterns for many populations. In addition to the well-studied seasonal cycles of mating and birth, there are also significant seasonal cycles of illness and death among field populations of mammals and birds. Energetically challenging winter conditions can directly induce death via hypothermia, starvation, or shock; surviving these demanding conditions likely puts individuals under great physiological stress. The stress of coping with energetically demanding conditions may increase adrenocortical steroid levels that could indirectly cause illness and death by compromising immune function. Individuals would enjoy a survival advantage if seasonally recurring stressors could be anticipated and countered by bolstering immune function. The primary environmental cue that permits physiological anticipation of season is daily photoperiod, a cue that is mediated by melatonin. However, other environmental factors may interact with photoperiod to affect immune function and disease processes. Immune function is compromised during the winter in field studies of birds and mammals. However, laboratory studies of seasonal changes in mammalian immunity consistently report that immune function is enhanced in short day lengths. To resolve this apparent discrepancy, we hypothesize that winter stressors present in field studies counteract short-day enhancement of immune function. Prolonged melatonin treatment mimics short days, and also enhances rodent immune function. Reproductive responsiveness to melatonin appears to affect immune function. In sum, melatonin may be part of an integrative system to coordinate reproductive, immunologic, and other physiological processes to cope successfully with energetic stressors during winter.

Stress and sensitization in children: a controlled prospective psychophysiological study of children exposed to international relocation.

This controlled prospective study investigated the development of sensitization as a result of international relocation in children, using the analyzing system Phadiatop. The effects of climate and predisposition to allergy were also measured. Children were examined prior to and during their first year of living abroad. A control group living at home was also examined during the same period. Participants answered a questionnaire before and after 1 year abroad, and blood samples were collected to determine sensitization. Before going abroad, there were no significant differences in atopic sensitization between groups nor in other key variables. After 1 year abroad, the proportion of children showing sensitization had increased significantly as compared with the control group at home. The exposed group reported an increase in skin symptoms during the year abroad. This study suggests that unidentified factors associated with foreign relocation increase the risk of sensitization in predisposed children. Stress might be one factor.