Climatic Change and Chicken Immunity
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(T-cells), start as a similar immature microorganisms as the B-cells. A range of Tcells is produced to perform various roles. Some T-cells act by producing chemicals
called lymphokines; others directly destroy disease organisms; some T-cells act to
enhance the response of B-cells, macrophages, or other T-cells (called helper T-cells);
while still others have the opposite effect and act to inhibit the activity of these cells
(suppressors) [58, 75, 86].
7.6 Mechanism of Heat Stress Impacting the Immune System
High environmental temperatures activate the hypothalamic-pituitary-adrenal (HPA)
axis. The stress-activated HPA axis was found to be responsible for the negative
effects of HS on broiler performance and immune function [34]. The HPA axis regulates corticotrophin releasing hormone and adrenocorticotropic hormone are released
from hypothalamic and pituitary cells [87]. In response to the physiological disruptions, more glucocorticoids are released. Glucocorticoids participate in the control of
body homeostasis and stress response of various organisms [43]. In chickens, HS has
been shown to cause elevated corticosterone concentrations [42, 44, 88, 89]. Changes
in corticosterone levels also occur due to environmental stimuli [90]. Increased corticosterone, as the final product of the HPA axis, causes numerous effects on behavior,
metabolic pathways, and immune functions [91].
7.7 Heat Stress and Heat Shock Protein
Heat-shock proteins (HSPs) are produced in abundance within the cell in response to
various stressors. Proteins are an evolutionarily conserved family of proteins whose
expression increases in response to a variety of different metabolic insults. Despite
their designation, most of the HSPs are constitutively expressed and perform essential functions [92, 93]. The function of the heat shock proteins is to activate ATP
hydrolysis and binding Hsc70 (constitutive form) to the aggregated protein [94].
HSP110 combined with HSP70 into an HSP110/HSP70 bichaperone and supported
by gene activity, creates a complex that can unfold even stably misfolded and aggregated proteins [95]. As a part of adaptation, cells are able to adjust to the changing
environmental conditions by modulating their gene expression. In chickens, transcriptomic approaches have been applied in studying heat stress with both in vivo
and in vitro models, which allowed identification of stress-related gene expression
changes in liver [96, 97], testes [98], brain [99], heart [97], muscle [97, 100] and
hepatocellular carcinoma cell line [101]. However, there has been no attempt to study
the molecular responses to heat stress and the accompanying endotoxemia directly
in the avian immune system.
Heat shock proteins greatly enhance the efficiency of intracellular protein manufacture and transport and may enhance immunity against pathogens by improving
511
(T-cells), start as a similar immature microorganisms as the B-cells. A range of Tcells is produced to perform various roles. Some T-cells act by producing chemicals
called lymphokines; others directly destroy disease organisms; some T-cells act to
enhance the response of B-cells, macrophages, or other T-cells (called helper T-cells);
while still others have the opposite effect and act to inhibit the activity of these cells
(suppressors) [58, 75, 86].
7.6 Mechanism of Heat Stress Impacting the Immune System
High environmental temperatures activate the hypothalamic-pituitary-adrenal (HPA)
axis. The stress-activated HPA axis was found to be responsible for the negative
effects of HS on broiler performance and immune function [34]. The HPA axis regulates corticotrophin releasing hormone and adrenocorticotropic hormone are released
from hypothalamic and pituitary cells [87]. In response to the physiological disruptions, more glucocorticoids are released. Glucocorticoids participate in the control of
body homeostasis and stress response of various organisms [43]. In chickens, HS has
been shown to cause elevated corticosterone concentrations [42, 44, 88, 89]. Changes
in corticosterone levels also occur due to environmental stimuli [90]. Increased corticosterone, as the final product of the HPA axis, causes numerous effects on behavior,
metabolic pathways, and immune functions [91].
7.7 Heat Stress and Heat Shock Protein
Heat-shock proteins (HSPs) are produced in abundance within the cell in response to
various stressors. Proteins are an evolutionarily conserved family of proteins whose
expression increases in response to a variety of different metabolic insults. Despite
their designation, most of the HSPs are constitutively expressed and perform essential functions [92, 93]. The function of the heat shock proteins is to activate ATP
hydrolysis and binding Hsc70 (constitutive form) to the aggregated protein [94].
HSP110 combined with HSP70 into an HSP110/HSP70 bichaperone and supported
by gene activity, creates a complex that can unfold even stably misfolded and aggregated proteins [95]. As a part of adaptation, cells are able to adjust to the changing
environmental conditions by modulating their gene expression. In chickens, transcriptomic approaches have been applied in studying heat stress with both in vivo
and in vitro models, which allowed identification of stress-related gene expression
changes in liver [96, 97], testes [98], brain [99], heart [97], muscle [97, 100] and
hepatocellular carcinoma cell line [101]. However, there has been no attempt to study
the molecular responses to heat stress and the accompanying endotoxemia directly
in the avian immune system.
Heat shock proteins greatly enhance the efficiency of intracellular protein manufacture and transport and may enhance immunity against pathogens by improving