Biomedical Engineering Reference
In-Depth Information
Heat Stress and Immune Function
Contents
1
Abstract
Heat stress suppresses different components
of the immune system and thereby enhances
susceptibility of an animal to various diseases.
Some of the responses of heat stress can be
prevented or overcome through alternative
management practices and some nutritional
strategies. Thermal stress imposes significant
economic burden on the productivity of cows
and buffaloes. Homeothermic processes within
a reasonable limit bring back the immune
system to a baseline response level after an
immune challenge due to heat stress. Haemato-
poietic system reacts by decreasing erythro-
cytes, haemoglobin and packed cell volume
during heat stress. The responses of the
immune system are of innate and adaptive
type. Livestock species of signi fi cant economic
importance like cattle and buffaloes have a
large population of lymphocytes in their blood,
and T-lymphocytes recognise antigens through
membrane receptors and are responsible for
the regulation of the immune response. The
immune system of cows contains a large pro-
portion of g d T-lymphocytes, and the number
varies with age and is considerably higher in
young animals than in adults, where they con-
stitute 5-10% of the total peripheral blood
lymphocytes. The higher concentration of
catecholamine exhibits a negative impact on
immunity of heat-exposed cells through IL-1a
and IL-1b. Glucocorticoids and catechola-
mines, through their effects on Th1 and Th2
cytokine secretion, may cause suppression of
Introduction
....................................................
114
2
Innate and Adaptive Immunity
.....................
115
3
Heat Stress and Cell-Mediated
Immunity
........................................................ 116
4
Role of Glucocorticoids
and Catecholamines in Regulation
of Stress Response
.......................................... 117
4.1 Role of Cytokines ................................... 117
4.2 Effect of Stress Hormones ...................... 118
4.3 Colostral Ig.............................................. 119
5
Acute and Chronic Stressors
.........................
119
6
Mechanism of Action of Heat
Stress on Immunity
........................................
120
7
Nutrition and Immunity
................................ 121
7.1 Vitamins .................................................. 122
7.2 Minerals .................................................. 124
8
Effect of Free Radical Production
on Immunity and Role of Antioxidants
........
128
9
Conclusions
.....................................................
130
References
...............................................................
130
