Heat Stress Causes Immune Abnormalities via Massive Damage to Effect Proliferation and Differentiation of Lymphocytes in Broiler Chickens

Abstract

Broiler chickens are highly sensitive to high ambient temperatures due to their feathers, lack of skin sweat glands, and high productivity. Heat stress (HS) is a major concern for the poultry industry because it negatively affects growth as well as immune functions, which increase the potential risk of infectious disease outbreaks. Therefore, it is vital to elucidate HS's effect on the avian immune system, especially considering the global rise in average surface temperature. Our study identified a series of immunological disorders in heat-stressed broiler chickens. We exposed 22-day-old broiler chickens to a continuous HS condition (34.5 ± 0.5 • C) for 14 days and immunized them with a prototype bovine serum albumin (BSA) antigen. The plasma and lymphoid tissues (thymus, bursa of Fabricius, and spleen) were harvested at the end of the experiments to investigate the induction of BSA-specific immune responses. Our results revealed that plasma titers of immunoglobulin (Ig)Y, IgM, and IgA antibodies specific for BSA were lower than those of thermoneutral chickens immunized with BSA. Furthermore, the spleens of the heat-stressed broiler chickens displayed severe depression of Bu1 + B cells and CD3 + T cells, including CD4 + T cells and CD8 + T cells, and lacked a fully developed germinal center (GC), which is crucial for B cell proliferation. These immunological abnormalities might be associated with severe depression of CD4 − CD8 − or CD4 + CD8 + cells, which are precursors of either helper or killer T cells in the thymus and Bu1 + B cells in the bursa of Fabricius. Importantly, HS severely damaged the morphology of the thymic cortex and bursal follicles, where functional maturation of T and B cells occur. These results indicate that HS causes multiple immune abnormalities in broiler chickens by impairing the developmental process and functional maturation of T and B cells in both primary and secondary lymphoid tissues.

Effect of a Synbiotic Supplement on Fear Response and Memory Assessment of Broiler Chickens Subjected to Heat Stress

“…Heat stress has a profound deleterious impact on broiler health and well-being. It suppresses immunity and disrupts physiological homeostasis, leading to hypersensitivity to neuroinflammation and metabolic disorders; consequently, production performance is impaired and diminished body weight, body weight gain, and increased feed conversion ratios are noted [50]. These alterations have a harmful effect on neurons and their function, causing brain ultrastructural damage and dysfunction, including mental and emotional disorders expressed at both memory and fear responsive levels [51,52].…”

Modulation of Heat-Shock Proteins Mediates Chicken Cell Survival against Thermal Stress

“…In poultry, growing research has specifically demonstrated the negative effects of high ambient temperatures on the immune response. Heat stress also induces several immune defects in the broiler by affecting the maturation of T and B cells in lymphoid tissue [ 30 ].…”

In Ovo and Oral Administration of Probiotic Lactobacilli Modulate Cell- and Antibody-Mediated Immune Responses in Newly Hatched Chicks

“…However, there is some evidence that post-hatch feed restriction can seriously impact performance and immune responses in neonatal chickens 2 . Additionally, post-hatch environmental stressors such as hatchery processing, treatments and vaccine administration, beak trimming, transportation, heat, and high stocking density can negatively in uence the immune system of newly hatched chicks, making them vulnerable to many pathogens 3,4 .…”