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Infrared Thermography for the Detection of Changes in Brown Adipose Tissue Activity
Published on: September 28, 2022
Body temperature during hibernation is highly correlated with a decrease in circulating innate immune cells in the
Berolla Sahdo1, Alina L Evans, Jon M Arnemo
1Department of Clinical Medicine, School of Health and Medical Sciences, Örebro University, SE-701 82 Örebro, Sweden.
International Journal of Medical Sciences
|March 28, 2013
Summary
Hibernating bears show reduced innate immune cells, with body temperature, not just torpor, driving immune changes across species. This suggests a regulated suppression of the immune system during winter dormancy.
Area of Science:
- Comparative immunology
- Mammalian physiology
- Hibernation biology
Background:
- Hibernation involves suppressed metabolism and reduced body temperature (Tb).
- Small hibernating mammals (<5kg) exhibit leukopenia, raising questions about whether torpor or low Tb causes decreased leukocyte counts.
- Brown bears (Ursus arctos), experiencing shallow Tb drops during torpor, were studied to differentiate these effects.
Purpose of the Study:
- To investigate immune cell count changes in brown bears during hibernation.
- To determine if decreased body temperature (Tb) or torpor itself drives immune cell reduction in hibernators.
- To compare immune function regulation across hibernating species.
Main Methods:
- White blood cell counts analyzed via flow cytometry in 13 brown bears over two years (summer vs. winter).
- Body temperature (Tb) monitored during hibernation.
- Data compared with 10 studies on 9 other hibernating species.
Main Results:
- Brown bears' Tb decreased from 39.6°C to 33.5°C during hibernation.
- Neutrophil and monocyte counts were significantly lower during hibernation.
- Body temperature decline strongly correlated with decreased innate immune cells across species (R²=0.83, p<0.0001).
Conclusions:
- Brown bears exhibit fewer circulating innate immune cells during hibernation, indicating potential immune suppression.
- Body temperature (Tb) appears to be the primary regulator of immune function during winter dormancy in both small and large hibernators.
- The unchanged lymphocyte counts in bears warrant further investigation into their role during hibernation.
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