The Hibernating Immune System

Abstract

Several physiological changes take place during hibernation, which are thought to allow animals to conserve energy and limit organ injury as might otherwise occur due to the physiological extremes of torpor and arousal. Significant changes occur in the immune system during torpor. The number of circulating leukocytes drops by *90% during entrance into torpor and seems to be driven by low body temperature. Normal cell counts restore upon arousal. Recently, we demonstrated that clearance of circulating lymphocytes is due to retention in lymphoid organs caused by a reduced plasma level of sphingosine-1-phosphate (S1P). Besides its effects on leukocyte migration, hibernation affects complement function, phagocytosis capacity, cytokine production, lymphocyte proliferation, and antibody production. The reduced immune function might play a major role in the etiology of White Nose Syndrome (WNS) in hibernating bats. Further, the ability to induce a fully reversible state of immune suppression in humans might aid the treatment of several inflammatory and immune-mediated diseases. Unraveling the

Tropical heterothermy is “cool”: The expression of daily torpor and hibernation in primates

“…Physiological functions related to immune responses may also be compromised during hibernation. Although it is unknown whether hibernating in warm conditions confers immunological protection to dwarf lemurs, immunological deficits to fight pathogens have been shown in several temperate hibernators . If this is the case, immune response during hibernation bouts in high plateau dwarf lemurs may be more jeopardized than that of dwarf lemurs hibernating in warmer environments.…”

“…Although it is unknown whether hibernating in warm conditions confers immunological protection to dwarf lemurs, immunological deficits to fight pathogens have been shown in several temperate hibernators. 61,62 If this is the case, immune response during hibernation bouts in high plateau dwarf lemurs may be more jeopardized than that of dwarf lemurs hibernating in warmer environments. Under these conditions, body temperature may reach high enough levels to fight pathogens during hibernation.…”

Thermal Ecology, Environments, Communities, and Global Change: Energy Intake and Expenditure in Endotherms

“…Parasites and pathogens may adversely impact the physiological condition of individuals and therefore may impact these individuals' tendency to undergo torpor. Hibernation alters the function of the immune system (reviewed by Bouma et al 2010Bouma et al , 2012: The number of circulating leukocytes drops by approximately 90%, and phagocytosis capacity, cytokine production, lymphocyte proliferation, and antibody production are all decreased.…”

“…The parasitized bats arouse from hibernation much more frequently than healthy bats do and so use up their fat stores too rapidly and starve to death . Thus, the reduced immune function during hibernation may play a role in the etiology of white-nose syndrome (Bouma et al 2012).…”

Modulation of mTOR and autophagy in hibernating hamster lung and the application of the potential mechanism to improve the recellularization process of decellularized lung scaffolds

“…Airway remodeling brings about structural changes in the number, mass, size and/or composition of the airway tissues which are manifested by an increase in collagen and SMA (smooth muscle actin) that could lead to peri-bronchial and peri-bronchoalveolar fibrosis and smooth muscle cell hyperplasia in asthma. The main characteristics of lung remodeling observed during torpor in the Syrian hamster are the increase in collagen and SMA accompanied by significant asthma-like structural changes such as increased matrix deposition in airway wall and increased airway smooth muscle mass leading to wall thickening together with changes in remodeling-associated proteins such as upregulation of TGF-β and ACE but without any significant involvement of immune doi: 10.7243/2050-1218-3-1 system response in the process of remodeling [2,4,5]. The changes observed in hamster lung were mainly located around the bronchioles, veins and the alveoli.…”