Ground squirrel splenic macrophages bind lipopolysaccharide over a wide range of temperatures at all phases of their annual hibernation cycle (original) (raw)
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Performance of bat-derived macrophages at different temperatures
Frontiers in Veterinary Science
Heterothermy, as a temperature-dependent physiological continuum, may affect host-pathogen interactions through modulation of immune responses. Here, we evaluated proliferation and functional performance of a macrophage cell line established from the greater mouse-eared (Myotis myotis) bat at 8, 17.5, and 37°C to simulate body temperatures during hibernation, daily torpor and euthermia. Macrophages were also frozen to −20°C and then examined for their ability to proliferate in the immediate post-thaw period. We show that bat macrophages can proliferate at lower temperatures, though their growth rate is significantly slower than at 37°C. The cells differed in their shape, size and ability to attach to the plate surface at both lower temperatures, being spheroidal and free in suspension at 8°C and epithelial-like, spindle-shaped and/or spheroidal at 17.5°C. While phagocytosis at temperatures of 8 and 17.5°C amounted to 85.8 and 83.1% of the activity observed at 37°C, respectively, ful...
American Journal of …, 2002
Golden-mantled ground squirrels (Spermophilus lateralis) undergo seasonal hibernation during which core body temperature (Tb) values are maintained 1-2°C above ambient temperature. Hibernation is not continuous. Squirrels arouse at ϳ7-day intervals, during which Tb increases to 37°C for ϳ16 h; thereafter, they return to hibernation and sustain low Tbs until the next arousal. Over the course of the hibernation season, arousals consume 60-80% of a squirrel's winter energy budget, but their functional significance is unknown and disputed. Host-defense mechanisms appear to be downregulated during the hibernation season and preclude normal immune responses. These experiments assessed immune function during hibernation and subsequent periodic arousals. The acute-phase response to bacterial lipopolysaccharide (LPS) was arrested during hibernation and fully restored on arousal to normothermia. LPS injection (ip) resulted in a 1-1.5°C fever in normothermic animals that was sustained for Ͼ8 h. LPS was without effect in hibernating squirrels, neither inducing fever nor provoking arousal, but a fever did develop several days later, when squirrels next aroused from hibernation; the duration of this arousal was increased sixfold above baseline values. Intracerebroventricular infusions of prostaglandin E2 provoked arousal from hibernation and induced fever, suggesting that neural signaling pathways that mediate febrile responses are functional during hibernation. Periodic arousals may activate a dormant immune system, which can then combat pathogens that may have been introduced immediately before or during hibernation. circannual rhythms; Spermophilus lateralis; neural-immune interactions MAINTENANCE OF IMMUNE FUNCTION requires considerable energy expenditure (42, 62) and may limit or constrain the extent to which animals engage in other energetically demanding activities . Large seasonal
Seasonal changes in the intestinal immune system of hibernating ground squirrels
Developmental & Comparative Immunology, 2007
Hibernation is associated with a prolonged fast (5-8 mo) which has the potential to affect intestinal immunity. We examined several aspects of the intestinal immune system in summer (non-hibernating) and hibernating ground squirrels. Peyer's patches were largely unaffected by hibernation, but numbers of intraepithelial lymphocytes (IEL) and lamina propria leukocytes (LPL) were greater in hibernators compared with summer. Hibernator IEL were less mature as demonstrated by low numbers of cells expressing activation-associated markers and co-receptors. Compared with summer, the percentage of B cells was higher and percentage of T cells was lower in the hibernator LPL. Hibernation was associated with greater mucosal levels of IFN-g, TNF-a, IL-10 and IL-4, but IL-6 and TGF-b were unchanged. Mucosal IgA levels were greater in entrance and torpid hibernators compared with summer. The results suggest that modifications of the intestinal immune system during hibernation may help preserve gut integrity throughout the winter fast. r
International Journal of Medical Sciences, 2000
Background: Hibernation involves periods of severely depressed metabolism (torpor) and decreases in body temperature (Tb). Small arctic mammals (<5kg), in which Tb generally drop drastically, display leukopenia during hibernation. This raised the question of whether the decreased leukocyte counts in mammalian hibernators is due to torpor per se or is secondary to low Tb. The present study examined immune cell counts in brown bears (Ursus arctos), where torpor is only associated with shallow decreases in Tb. The results were compared across hibernator species for which immune and Tb data were available. Methods and Results: The white blood cell counts were determined by flow cytometry in 13 bears captured in the field both during summer and winter over 2 years time. Tb dropped from 39.6±0.8 to 33.5±1.1°C during hibernation. Blood neutrophils and monocytes were lower during hibernation than during the active period (47%, p= 0.001; 43%, p=0.039, respectively), whereas no change in lymphocyte counts was detected (p=0.599). Further, combining our data and those from 10 studies on 9 hibernating species suggested that the decline in Tb explained the decrease in innate immune cells (R 2 =0.83, p<0.0001). Conclusions: Bears have fewer innate immune cells in circulation during hibernation, which may represent a suppressed innate immune system. Across species comparison suggests that, both in small and large hibernators, Tb is the main driver of immune function regulation during winter dormancy. The lack of a difference in lymphocyte counts in this context requires further investigations.
Journal of Zoology, 2011
Fever is part of an acute phase response that organisms launch to defend themselves against an invasion by microbial pathogens such as bacteria and viruses. The elevation of an individual's body temperature necessary to achieve a fever is considered energetically costly and variation in the expression of the febrile response has been reported with respect to season, sex and the reproductive status of an animal. The effect of these parameters on fever responses are well characterized for laboratory rodents but comparable data from wild rodents are currently lacking. We evaluated the febrile response of wild highveld mole-rats (Cryptomys hottentotus pretoriae) to lipopolysaccharide (LPS) during winter and summer. This social rodent retains its breeding potential throughout the year and exhibits a reproductive division of labour. Highveld mole-rats increased their body temperature to a greater degree in response to a dose of 1 mg kg-1 LPS than to saline or handling alone. The fever response did not differ between seasons while the stress-induced hyperthermia in response to handling was greater in summer compared winter. In contrast, males and breeders exhibited larger changes in body temperature following LPS administration than females and non-breeders, respectively. These findings are in accordance with those reported for laboratory species and suggest that general principlesgovern the modulation of innate immune responses such as fever among small mammals.
Photoperiod and Temperature Interact to Affect Immune Parameters in Adult Male Deer Mice
Journal of Biological Rhythms, 1996
Nontropical rodents often experience large seasonal fluctuations in both food availability and energy demands. The energy required for thermoregulation is highest during the winter when food availability may be at an annual minimum. Failure to cope with winter probably accounts, in part, for the increased prevalence of disease and death relative to that in summer. Winter conditions may elevate circulating glucocorticosteroid levels, which can compromise immune function. To increase the odds of surviving the energetic demands of winter, individuals of some rodent species appear to enhance immune function before conditions deteriorate. Previous laboratory studies suggest that immune enhancement can be induced by short days. These findings contrast with the results of several field studies reporting suppressed immune function during the winter. To resolve this conflict, the authors hypothesized that winter stressors present in field studies counteracted the short-day enhancement of imm...
Physiology & Behavior, 1997
HUSBAND. The effects of lipopolysacchride (LPS) on fever response in rats at different ambient temperatures. PHYSIOL BEHAV 62(6) [1197][1198][1199][1200][1201] 1997.-There is a complex interplay between the immune system, nervous system, and sleep. When an organism is challenged with lipopolysacchride (LPS), the immune system is stimulated, producing a fever response that is independent of ambient temperature, and an increase in slow-wave sleep (SWS). The study investigated sleep patterns of immune-challenged rats during the light phase cycle to determine the effects of various ambient temperatures. It was hypothesised that fever response would occur independently of ambient temperatures. Also, the febrile response would be monophasic, and there would be an increase in slow-wave sleep (SWS) and a decrease in rapid-eyemovement (REM) sleep. Thirty Wistar rats were randomly placed in 3 different ambient temperature groups, 22ЊC, 15ЊC, and 30ЊC. Within each of these conditions, the same subjects served as control and experimental groups. Four animals were placed in 4 subsections of 2 standard boxes that were placed in the ambient-temperature box. The electrodes were connected to the analog to digital computer board, where all the data was processed and stored on a hard drive. The animals were injected IP with saline and recorded for a period of 6 h to establish a baseline. On Day 2, the same animals were injected IP with LPS and recorded for 6 h to determine the febrile effects of LPS on the immune system; the same procedure was repeated in the other ambient temperatures. The results have shown that animals experienced a monophasic fever response in low and normal temperatures, but not in the high temperatures. Although there was no increase in SWS, there was a significant decrease in REM sleep in 3 groups. ᭧ 1997 Elsevier Science Inc.