The impact of heat stress on the immune system in dairy cattle: A review

Floods, Hurricanes, and Other Catastrophes: A Challenge for the Immune System of Livestock and Other Animals

“…Antigens supplied with the diet stimulate the production of immunoglobulin's in the bursa (16)(17)(18). Food intake is than necessary for a correct and efficacious immune response (19).…”

“…Another common response to heat stress in different farm animal species (cattle, goats, sheep, pig, poultry) is the increase in peripheral cortisol levels (19)(20)(21)(22). Indeed, the heat stress causes the activation of the two axes hypothalamic-pituitaryadrenal (HPA) and sympathetic-adrenal-medullar (SAM), with the final release of cortisol and catecholamines that are known to influence the biology of leukocytes.…”

“…In dairy cows the activation of HPA and SAM axes induce the release of glucocorticoids and catecholamines and the following reduction of cytokine levels, particularly IL-4, IL-5, IL-6, IL-12, IFN-γ, and TNF-α (19). High levels of cortisol lead to immune suppression, overall on T cell compartment, cytokine production, and phagocytosis.…”

“…Also, catecholamines negatively affect the immune system by inhibiting IL-12 production and promotion of IL-10 release, finally promoting a Th2 response. The hyperthermia concurs to the inhibition of Th1 response, favoring the Th2 mediated humoral response (19). Cortisol aggravates the immunosuppression by inhibiting the activation of T cell, the production of cytokines and the phagocytosis (19).…”

“…The hyperthermia concurs to the inhibition of Th1 response, favoring the Th2 mediated humoral response (19). Cortisol aggravates the immunosuppression by inhibiting the activation of T cell, the production of cytokines and the phagocytosis (19). In these conditions of immunosuppression vaccination of animals is inefficacious and some latent viruses can reactivate (19).…”