Heat Stress Impacts on Embryo Development in Livestock PDF

Heat Stress Impacts on Embryo Development in Livestock Physiological Effects of Heat Stress on Reproduction Uterine environment: Thermoregulatory Endocrine disruptions: Heat stress changes the response: Increased Cor...

Heat Stress Impacts on Embryo Development in Livestock Physiological Effects of Heat Stress on Reproduction Uterine environment: Thermoregulatory Endocrine disruptions: Heat stress changes the response: Increased Cortisol, LH, and uterine fluid’s respiration, sweating, progesterone altered composition, affecting and reduced feed intake under heat stress. implantation. affect metabolism.  Kasimanickam & Kasimanickam Scientific Reports volume 11, Article number: 14839 (2021)  Heat Stress Impact on Embryonic Development Pre-implantation Embryo Sensitivity: Heat stress disrupts homeostasis leading to hyperthermia and affecting embryo development at multiple stages. Blastocyst stage is particularly sensitive to heat, leading to impaired cell division and differentiation.  Direct Effects on Embryo Development Early Embryonic Loss: The embryo is highly vulnerable during days 1–7 post-fertilization. Zygote stage: Heat stress disrupts mitotic divisions and causes chromosomal aberrations. Oxidative stress: ROS damage mitochondria and DNA in embryonic cells. Heat Shock Proteins: Provide temporary protection but overwhelmed by prolonged stress.  Impaired Implantation and Embryo Survival Uterine temperature increases lead to embryonic death. Reduced maternal recognition of pregnancy: Interferon tau (IFN-τ) signaling impaired. Implantation: Heat stress reduces trophoblast adhesion and implantation success.  Placental Insufficiency and Fetal Development Reduced placental blood flow: Leads to nutrient and oxygen restriction. Hypoxia: Placental insufficiency causes hypoxia, limiting fetal growth. Nutrient restriction: Reduced availability of glucose, amino acids, and fatty acids leads to IUGR.  Molecular Mechanisms Affected by Heat Stress in Embryos Reactive Oxygen Species (ROS): Heat stress induces oxidative stress through the overproduction of ROS. ROS can damage DNA, proteins, and lipids within embryonic cells, compromising cellular integrity and embryo viability. Antioxidant defense mechanisms may be overwhelmed, leading to apoptosis or necrosis in the early embryo.  Molecular Mechanisms Affected by Heat Stress in Embryos Heat Shock Proteins (HSPs): Heat stress induces the production of heat shock proteins (HSPs), particularly HSP70, which function as molecular chaperones. HSP70 helps to stabilize proteins and refold denatured proteins under stress, but its overexpression can also interfere with normal embryonic processes, including gene expression and cell division.  Molecular Mechanisms Affected by Heat Stress in Embryos Endoplasmic Reticulum (ER) Stress: ER stress and the unfolded protein response (UPR) are activated by heat stress, which may lead to impaired protein folding in embryonic cells. Prolonged UPR activation can trigger apoptosis, further reducing embryonic survival rates.  Endoplasmic Reticulum (ER) Stress The endoplasmic reticulum (ER) is an organelle responsible for protein folding and processing within cells. Under normal conditions, it ensures that newly synthesized proteins are correctly folded and functional. ER stress occurs when the ER becomes overwhelmed due to factors like heat stress, which disrupts the protein-folding process. This can lead to an accumulation of misfolded or unfolded proteins in the ER. Unfolded Protein Response (UPR): To cope with ER stress, cells initiate a protective mechanism called the Unfolded Protein Response (UPR). The UPR's primary goal is to restore normal function in the ER by: Halting protein translation to reduce the load of new proteins entering the ER. Increasing the production of molecular chaperones that help in protein folding. Degrading misfolded proteins that accumulate. Prolonged Stress Leading to Apoptosis: While the UPR is initially a protective response, prolonged or severe ER stress can overwhelm the cell’s capacity to manage the unfolded proteins.  Genetic Regulation and Genes Impacted by Heat Stress Heat Shock Protein Genes (HSPs): HSP70, HSP90, and HSP27: These genes are upregulated in response to heat stress to help maintain protein homeostasis. HSP70 is especially important, as it is involved in protecting embryonic cells from the damaging effects of heat-induced protein misfolding. Overexpression of these genes during embryonic development has been linked to decreased developmental competence, as the stress response can interfere with normal cellular functions.  Genetic Regulation and Genes Impacted by Heat Stress Apoptosis-Related Genes: BAX and BCL-2: These genes are involved in regulating the apoptotic pathway. Heat stress increases the expression of BAX (pro-apoptotic) and decreases the expression of BCL-2 (anti- apoptotic), leading to a higher rate of programmed cell death in embryos. Caspase Genes: Heat stress also upregulates the activity of caspases, a family of enzymes central to the execution of apoptosis, contributing to embryo mortality.  Genetic Regulation and Genes Impacted by Heat Stress Oxidative Stress-Related Genes: SOD1, CAT, and GPX: These genes encode antioxidant enzymes that neutralize ROS. SOD1 (superoxide dismutase) converts superoxide radicals into less harmful molecules, while CAT (catalase) and GPX (glutathione peroxidase) reduce hydrogen peroxide into water. Under heat stress, embryos exhibit increased oxidative stress, which leads to the overexpression of these genes as a compensatory response. However, when the oxidative load is too high, these systems are overwhelmed.  Genetic Regulation and Genes Impacted by Heat Stress Placental Development Genes: VEGF (Vascular Endothelial Growth Factor): This gene is crucial for angiogenesis and the establishment of the placenta. Heat stress downregulates VEGF, impairing placental vascularization, which is essential for nutrient and oxygen exchange between the mother and the developing fetus.  Genetic Regulation and Genes Impacted by Heat Stress Genes Involved in Cell Cycle and DNA Repair: P53: Known as the "guardian of the genome," P53 plays a role in DNA repair and cell cycle regulation. Heat stress upregulates P53, which can lead to cell cycle arrest in embryos as the cells attempt to repair heat- induced DNA damage. If the damage is irreparable, P53 can trigger apoptosis.  Epigenetic Changes Induced by Heat Stress Heat stress can lead to: DNA Methylation: Altered methylation patterns affect gene expression. Histone Modification: Changes in acetylation and methylation can alter gene expression and affect embryonic development.  Heat Stress and its Effects on Placentation and Fetal Development in Livestock  Introduction Heat stress significantly affects placentation in livestock, impairing the placenta's ability to support fetal development. This can lead to growth restriction, organ developmental issues, and metabolic problems in the fetus.  Pre-implantation Events Blastocyst Development: After fertilization, the zygote undergoes cleavage to form a blastocyst, which consists of an inner cell mass (future embryo) and the outer trophoblast cells (which will give rise to the placenta). In ruminants, the blastocyst undergoes significant elongation before implantation, a critical step for placental development. Trophoblast Differentiation: The trophoblast cells begin differentiating into specialized cell types such as mononuclear trophoblast cells and binucleate trophoblast cells. These cells play essential roles in forming the placenta and mediating interactions with the maternal endometrium (uterine lining). Elongation of the Conceptus Conceptus Growth: In ruminants, the conceptus (the early embryo and its extraembryonic membranes) undergoes rapid elongation during the peri-implantation period. This is critical for proper apposition to the maternal endometrium, as the embryo expands to form a long filamentous structure. Molecular Signals Involved: Interferon-tau (IFN-τ): This is a critical molecule produced by the elongating trophoblast. It acts as the primary signal for maternal recognition of pregnancy in ruminants. IFN-τ inhibits the production of prostaglandin F2α (PGF2α), which is responsible for luteolysis (regression of the corpus luteum), thus maintaining progesterone production and sustaining pregnancy. Progesterone: Produced by the corpus luteum, progesterone is essential for the maintenance of pregnancy and modulates gene expression in the uterine epithelium to support the developing conceptus. Fibroblast Growth Factors (FGFs): FGFs, especially FGF2, play a role in conceptus elongation and uterine receptivity by promoting trophoblast proliferation and differentiation. Apposition, Adhesion, and Attachment to the Uterine Epithelium Apposition: The elongated conceptus comes into close contact with the uterine luminal epithelium. This process is non-invasive in ruminants, meaning that the embryo does not deeply embed into the maternal tissue as seen in humans or rodents. Adhesion: Molecular adhesion between the trophoblast cells and the uterine luminal epithelium occurs through interactions involving adhesion molecules such as integrins and trophoblast-specific proteins. These proteins facilitate the stable attachment of the conceptus to the maternal surface. Integrins: These transmembrane receptors mediate interactions between the extracellular matrix and the cytoskeleton. In ruminants, integrins expressed by both trophoblast cells and the uterine epithelium are essential for establishing firm contact between the conceptus and the maternal tissues. Mucins (MUC1): Mucins are glycoproteins that initially act as a barrier to conceptus attachment. However, during pregnancy, their expression is downregulated in specific regions to allow adhesion of the conceptus to the uterine surface. Formation of Placentomes Cotyledon and Caruncle Interaction: In ruminants, the placenta is of the cotyledonary type, characterized by the formation of placentomes, where fetal cotyledons (on the trophoblast side) and maternal caruncles (on the uterine side) form a close functional unit. Binucleate Trophoblast Cells (BNCs): These cells originate from the trophoblast and migrate into the maternal endometrium. BNCs secrete key molecules such as placental lactogen and pregnancy-specific protein B (PSPB), which are important for maternal-fetal communication and placental development. Placental Lactogen: This hormone is involved in fetal growth and maternal metabolism during pregnancy. It also regulates nutrient partitioning between the dam and fetus. PSPB: This protein is an indicator of pregnancy in ruminants and plays a role in placental growth and function.  Vascularization and Nutrient Exchange Angiogenesis and Vascularization: As the placentomes develop, the formation of an extensive vascular network is crucial to facilitate the exchange of nutrients, gases, and waste products between the dam and the fetus. Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis in the developing placenta. VEGF: It stimulates the formation of blood vessels in both the maternal and fetal compartments of the placenta, ensuring adequate blood supply to support fetal development. Platelet-Derived Growth Factor (PDGF): PDGF also plays a role in promoting the formation of blood vessels and supporting placental development. Hormonal Influence: Progesterone and other hormones, such as estrogen and placental lactogen, influence the vascular development of the placenta and regulate the growth of both maternal and fetal tissues. Heat Stress and Placentation Effects on Placental Vascularization and Nutrient Exchange Reduced Placental Vascularization: The placenta must develop an extensive vascular network to support fetal growth and nutrient exchange. Heat stress has been shown to reduce the expression of angiogenic factors like vascular endothelial growth factor (VEGF), leading to impaired blood vessel formation in the placenta. Reduced placental vascularization decreases the capacity for efficient nutrient and oxygen exchange between the mother and fetus, which can compromise fetal development. Decreased Nutrient and Oxygen Supply: Heat stress can reduce blood flow to the uterus and placenta due to the redirection of blood flow to peripheral tissues in an effort to dissipate heat. This reduction in uterine blood flow can impair the delivery of essential nutrients and oxygen to the developing fetus, leading to restricted fetal growth and potential developmental abnormalities. Alteration of Placental Hormone Production Disruption of Progesterone Production: Progesterone is a key hormone in maintaining pregnancy and ensuring proper placental development. Heat stress can disrupt the synthesis of progesterone by the corpus luteum or placenta, leading to suboptimal placental function. Low progesterone levels may impair placental growth, vascular development, and the maintenance of pregnancy. Altered Placental Lactogen Levels: Placental lactogen, a hormone produced by the placenta, is crucial for fetal growth and maternal metabolism during pregnancy. Heat stress can reduce the expression of placental lactogen, further limiting fetal growth and nutrient partitioning between the dam and the fetus. Increased Production of Reactive Oxygen Species (ROS) Oxidative Stress: Heat stress increases the production of reactive oxygen species (ROS) in the placenta, leading to oxidative stress. This oxidative damage can impair placental cell function, cause inflammation, and reduce the capacity of the placenta to support the growing fetus. Cellular Damage: Elevated ROS levels can damage trophoblast cells (the cells that form the placenta), potentially disrupting their differentiation and migration. This can interfere with the formation of placentomes, which are essential for nutrient exchange in ruminants. Impaired Placental Attachment and Function Impaired Trophoblast Function: Heat stress can impair the differentiation and function of trophoblast cells, which are critical for establishing the maternal-fetal interface in ruminants. These cells must differentiate into mononuclear and binucleate cells to form placentomes, the primary site of nutrient and gas exchange. Any impairment in their function due to heat stress can compromise placental attachment and overall function. Altered Expression of Adhesion Molecules: Successful placentation depends on the expression of adhesion molecules such as integrins, which mediate the attachment of the trophoblast to the uterine epithelium. Heat stress can alter the expression of these molecules, reducing the strength of the conceptus-uterine attachment and potentially leading to placental insufficiency or pregnancy failure. Effects on Placental Efficiency and Fetal Growth Placental Efficiency: Heat stress can reduce the overall efficiency of the placenta in supporting fetal growth. Heat-stressed animals tend to have placentas with reduced surface area and diminished functional capacity for nutrient and oxygen exchange. This reduction in placental efficiency can lead to intrauterine growth restriction (IUGR) and lower birth weights. Reduced Fetal Growth: Due to the combination of reduced nutrient exchange, vascularization, and placental function, fetuses from heat-stressed pregnancies often exhibit lower growth rates. This can result in smaller, less viable offspring and may increase the risk of neonatal mortality. Timing of Heat Stress and Severity of Impact Early Gestation: Heat stress during the early stages of pregnancy (especially around conception and implantation) is particularly detrimental to placental development. The disruption of conceptus elongation, maternal recognition of pregnancy, and trophoblast differentiation can result in early embryonic loss or severely impaired placental function. Mid to Late Gestation: Heat stress later in pregnancy tends to impact fetal growth more directly by reducing placental efficiency and vascularization. While pregnancy loss is less common at this stage, intrauterine growth restriction and compromised fetal health are significant concerns. Impacts on Fetal Development Due to Heat Stress 1. Intrauterine Growth Restriction (IUGR): - Reduced nutrient and oxygen supply to the fetus. - Smaller placenta limits exchange of nutrients and gases. 2. Delayed Organogenesis: - Brain development: Impact on cognitive function. - Lung and heart development: Delayed maturation increases postnatal risk. - Reduced muscle mass and adipose tissue deposition. 3. Metabolic Programming: - Heat stress affects fetal metabolism, increasing the risk of postnatal disorders.  Continued Impacts on Fetal Development 4. Immune Function: - Heat stress compromises immune system development in the fetus. - Increases postnatal susceptibility to infections and diseases. 5. Thermoregulatory Capacity: - Fetal programming for reduced ability to cope with heat stress postnatally. 6. Long-term Impacts on Growth: - Lower birth weight and postnatal growth delays due to placental insufficiency. Epigenetic Effects of Heat Stress Heat stress can cause epigenetic changes in fetal development, which can have long-lasting effects. These include DNA methylation, histone modifications, and non-coding RNA alterations. 1. DNA Methylation: - Alters methylation patterns, impacting gene expression related to growth and development. - Can lead to restricted growth and metabolic changes. Histone Modifications and Non- coding RNAs 2. Histone Modifications: - Acetylation and methylation of histones affect chromatin structure and gene expression. - Can lead to repression of genes critical for placental and fetal development. 3. Non-coding RNAs (miRNAs): - Altered expression of microRNAs can impact developmental pathways. - Disruption in miRNAs involved in nutrient transport and growth regulation.  Molecular Mechanisms of Epigenetic Changes 1. Oxidative Stress: - Heat stress induces reactive oxygen species (ROS) production, damaging DNA and proteins. - ROS activate DNA methyltransferases (DNMTs) and histone deacetylases (HDACs). 2. Nutrient Sensing Pathways: - Heat stress alters nutrient availability, affecting insulin-like growth factor (IGF) pathways. - Epigenetic silencing of growth-promoting genes contributes to restricted fetal growth. Hormonal Changes and Long-Term Consequences 3. Hormonal Changes: - Reduced progesterone and estrogen disrupt placental and fetal development. - These hormones regulate epigenetic modifiers, such as miRNAs and histone modifications. Long-Term Consequences: - Animals exposed to heat stress in utero may experience lifelong metabolic and reproductive issues. - Altered gene expression due to epigenetic changes can persist into adulthood and may even affect future generations. Male Fertility  Introduction - Spermatogenesis is highly sensitive to heat and cold leading to decreased sperm quality and male infertility. 4-6 degrees C cooler than body temperature in testes  Spermatogenesis Testis: produce sperm and testosterone Gave testes back to chicken and developed male characteristics Not a lot of room for cytoplasmic events to move around- higher concentration to ROS, sensitive to environment  What does this have to do with actual production? Bull Ram Boar Stallion Man cycle (days) 13.5 10.4 8.3 12.2 16 Spermatogenesis 61 47 39 57 75 If environmental insult occurs 2 months ago, we may affect spermatogenesis  Metabolism Sperm cells rely on three primary energy pathways: Glycolysis: The anaerobic conversion of glucose to pyruvate. Pyruvate can be further converted to lactate under aerobic conditions. Krebs Cycle (Citric Acid Cycle): Takes place in mitochondria, converting pyruvate to Acetyl CoA, leading to ATP production through a series of oxidation-reduction reactions. Oxidative Phosphorylation (OXPHOS): Uses the electron transport chain (ETC) to produce ATP. NADH and FADH2 generated from the Krebs cycle donate electrons to the ETC. Short lived bc they have to rely on their environment Has a balance of ROS -free radicals build up Delicate balance between ROS & _ Role of Reactive Oxygen Species (ROS) ROS, including superoxide anion (O2 −) and hydrogen peroxide (H2O2), are byproducts of sperm metabolism, especially from the ETC in mitochondria. Although ROS can cause oxidative damage, controlled ROS production plays a regulatory role in sperm function. Overproduction or insufficient management of ROS can lead to sperm damage and dysfunction. Produce more ROS during metabolism bc it plays a regulatory role in sperm fxn Metabolic Plasticity Metabolic Flexibility: Sperm cells exhibit adaptability in energy production. They can shift between glycolysis and oxidative phosphorylation depending on available substrates and environmental conditions (e.g., glucose, lactate, or fatty acids). For example, lactate is considered more efficient than glucose in sustaining horse sperm motility  *Freezing medias Glycolysis Byproducts and Methylglyoxal (MG) Toxicity Excess glucose leads to the formation of 2-oxoaldehydes such as glyoxal and methylglyoxal, which are byproducts of glycolysis and lipid metabolism. These compounds can cause significant sperm damage due to their electrophilic nature, leading to protein and DNA modifications. High levels of glucose in semen extenders (80-300 mM) can exacerbate these effects, mirroring diabetic conditions where sperm malfunction is prevalent.  Heat Stress Effects on Bovine Fertility - Main Mechanisms: - Accumulation of reactive oxygen species (ROS), causing lipid peroxidation. - DNA damage and reduced energy production due to mitochondrial dysfunction. - Oxidative stress leading to apoptosis (cell death). Sperm metabolism Sperm need ROS in balance  Cellular Defense Mechanisms - Heat Shock Proteins (HSP): - HSPs are essential for maintaining protein stability during heat stress. - Protect cells by refolding proteins and preventing apoptosis. - HSP90 is critical for sperm motility and quality after heat exposure.  Heat Stress Hormones Reduced GnRH (LH and FSH) Reduced Testosterone Elevated prolactin levels which can further suppress Testosterone – Electrolyte balance as well prolactin playing role in electrolyte balance  Decreasing leydig cell T production Chen et al., 2023  Cold Stress Scrotal Temperature Regulation: Cold stress can impair the ability of livestock to regulate scrotal temperature. The scrotum’s Damage testicular function is to maintain optimal temperatures for sperm tissue, through production, and cold temperatures can lead to testicular frostbite constriction, reducing blood flow and damaging the tissues. Reduced Blood Flow: Prolonged exposure to cold can lead to vasoconstriction (narrowing of blood vessels), which reduces blood flow to the testes, leading to potential tissue damage, reduced oxygen supply, and oxidative stress in the testicular cells. Too long of cold stress can damage blood supply  Hormone Testosterone Levels: Cold stress can cause hormonal imbalances, particularly by reducing testosterone production. Testosterone is critical for spermatogenesis and overall male reproductive function. A decrease in testosterone levels can negatively affect libido, mating behavior, and sperm production. Altered Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH): Cold stress can also affect the secretion of LH and FSH, which are essential for the regulation of testicular function and sperm production.  Methylation Alters DNA methylation in sperm Hossain et al., 2024 DNA in cold env. Can alter DNA methylation. Short term epigenetics Gene ontology College of Agricultural, Consumer and Environmental Sciences BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Introduction to Immunology BE BOLD. Shape the Future. The College of Agricultural, Consumer and Environmental Sciences is an engine for economic and community development New Mexico State University in New Mexico, improving the lives of New Mexicans through academic, research, and Extension programs. aces.nmsu.edu Immunology Immune mechanisms range from independently acting proteins to individual cells equipped to destroy infected cells Immune system = all tissues, cells, and molecules that work together to effect an immune response* What does an immune response do? Protect the animal Regulates other physiological events BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Origin of Immune Cells White blood cells = leukocytes (all immune cells) Most arise from hematopoietic stem cells in bone marrow Some tissue-specific macrophages (microglia for example) yolk sack or fetal liver Seed before birth and regenerate in the tissue After leaving marrow travel in blood or lymphatic system Lymphatic system drains extracellular fluid and immune cells from tissue, transports them as lymph, and emptied back to blood BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Immune System “Red Blood Cells” and “White Blood Cells” Billions of cells to mount effective defense Communication is critical! Cytokines (are these hormones??) Soluble mediators Direct cell-to-cell contact 2 Major Arms Adaptive Innate BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu The Communication Signals Interleukins: inter-leukocyte (IL) Interferons: interfere (IFN) Chemokines: chemical (chemo) movement (kinos) Colony-stimulating factors: cell proliferation (CSF) Others Transforming growth factor B Tumor necrosis factor Monoamines (histamine and serotonin) Leukotrienes and prostaglandins BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Key Points Immune cells derive from hematopoietic stem cell in bone gives rise to 3 progenitor cells: myeloid, lymphoid, and erythroid/megakaryocyte Immune system can be subdivided into adaptive and innate systems Immune system utilizes chemical signals to communicate BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Intercellular and Intracellular Coordinated response to these: BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu College of Agricultural, Consumer and Environmental Sciences BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Innate Immunity BE BOLD. Shape the Future. The College of Agricultural, Consumer and Environmental Sciences is an engine for economic and community development New Mexico State University in New Mexico, improving the lives of New Mexicans through academic, research, and Extension programs. aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Cells of the Innate Immune System Cell Function Neutrophil Phagocytosis, Degranulation Eosinophil Degranulation Basophil Degranulation Monocytes Precursor—limited antimicrobe Macrophage Phagocytosis, inflammatory mediators, detect threats Dendritic Phagocytosis, inflammatory mediators, detect threats BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Cells of the Innate Immune System Cell Function Mast Cells Degranulation Natural Recognize “distressed” cell and Killer Cells kill BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Phagosome BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Macrophages Resident in almost all tissues Some reside from embryonic development Bone marrow => Monocytes => Macrophage Phagocytic function = innate Initiate inflammation and immune response = adaptive BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Granulocytes Neutrophils, eosinophils, and basophils Short lived and increase in infection Neutrophils are phagocytic and most abundant Eosinophils and basophils more for parasite infection and can cause damage in allergic reactions BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Mast Cells Histamine Begin in bone marrow but migrate to tissues: skin, intestines, and airway BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Dendritic cells Phagocytic Dendrite-like appearance Bone marrow and migrate to tissues Macropinocytosis: continually ingest extracellular fluid and contents. Degrade pathogen, process, and produce mediators to activate immune response BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Self vs. Nonself Pure proteins don’t elicit an immune response = not immunogenic Need adjuvant Macrophages, neutrophils, and dendritic cells are sensor cells Detect infection and initiate immune response PRRs: pattern recognition receptors Recognize PAMPs (mannose-rich oligosaccharides, peptidoglycans, LPS, and UNMETHYLATED CpG DNA BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Self vs Nonself PRRs (pattern recognition receptors) Toll-like Receptors: extracellular PAMPS or bacteria in intracellular vesicles NOD-like receptors (NLRs): intracellular bacterial invasion, viral RNA, host RNA in wrong location, host vs. microbial DNA, or cellular damage signals BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Pathogen Recognition BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Common Lymphoid Progenitor Antigen-specific lymphocytes (discussed next) Several innate lineages that lack antigen-specific receptors: Natural Killer Cells Like T-cells can bind to and kill pathogens Can stimulate or amplify immune response Lack specificity Several lineages have been identified = Innate Lymphoid Cells (ILCs) BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Natural Killer Cells BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Inflammation Allows leukocyte infiltration Allows access for complement and acute phase proteins Isolate damage or infection Signs Redness Swelling Heat Pain Loss of function BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu  Intro to Adaptive is Next BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu  Adaptive Immune BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Antigen-specific lymphocytes Respond to vast array of antigens Immunological memory Exposed once then will generate immediate and stronger response in future Developing effective vaccines is the challenge Response is driven by vast array of highly variable antigen receptors BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Antigen and antigen receptor interactions Two classes of lymphocytes (antigen specific) B and T cells B cells have B cell receptor; T cells have T cell receptor Circulate as small cells, few cytoplasmic organelles, and condensed inactive-appearing chromatin. Very little activity prior to stimulation = naïve lymphocytes Meet antigen, become activated, = effector lymphocytes BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu B- and T- cell receptors B-cell antigen receptor (B-cell receptor; BCR) Formed by same genes that encode antibodies or immunoglobulins (Ig) Antigen receptor can also be termed membrane immunoglobulin (mIg) or surface immunoglobulin (sIg) T-cell antigen receptor (T-cell receptor; TCR) Related to mIg but distinct structure and recognition properties BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Antigen binding to receptor B-cells Proliferate Differentiate into PLASMA cells Secrete antibodies that have same specificity as the plasma cell’s BCR Means antigen that binds to and stimulates receptor is now the target of the antibodies produced T-cells Proliferates and differentiates into one of several effector T-cells Cytotoxic T-cell (kill infected cells), Helper T-cell (activate other cells), Regulatory T-cell (suppress activity of other cells) Both cells will differentiate into memory cells; memory cells then differentiate into effector cells (rapidly) when re-exposed BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu  ITAM = Immunoreceptor tyrosine-based Variable Region activation motif Variable Region Constant Region: Effector function BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Antibodies and T-cell receptors 2 distinct regions Constant region also called fragment crystallization region or Fc 4 or 5 forms Variable region: vast number of amino acid sequences Antibody molecule 2 identical light chains and 2 identical heavy chains Variable region on the heavy and light chains form antigen binding site Each antibody has 2 identical antigen-binding sites Constant region determines how the antibody will interact with various immune cells to dispose of the antigen once bound BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Antibodies and T-cell receptors T-cell receptor Composed of TCR alpha and TCR beta chains Span the TC membrane Variable and constant region Combination of alpha and beta variable region combine to form a SINGLE antigen binding site No secreted form Interact with MHC BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Antigen Recognition Essentially any chemical structure can be an antigens Common: proteins, glycoproteins, and polysaccharides Antibody or antigen receptor recognizes small part of antigen’s molecular structure Called antigenic determinant or epitope BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu MHC molecules Antibodies can recognize almost anything T-cell receptors recognize epitope derived from partially degraded protein bound to MHC Major histocompatibility complex: cell-surface glycoprotein Antigen can derive from intracellular OR extracellular pathogens BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Antigen receptor genes Innate immune system PRR = fewer than 100 different types of proteins Antigen-specific receptors are nearly infinite but only encoded by a finite number of genes Variable region genes are inherited as sets of gene segments that encode a part of the variable region on one chain During B-cell development in bone marrow, gene segments are irreversibly joined by DNA recombination Similar for T-cells in the thymus BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Antigen receptor genes Relatively few (hundred) gene segments can combine in different ways to yield thousands of different receptor chains = combinatorial diversity Can also add or subtract nucleotides at junctions = junctional diversity BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Lymphocyte development Assembly of antigen receptor from incomplete gene segments carried out to ensure each developing lymphocyte expresses only 1 receptor specificity Gene rearrangement irreversibly changes the lymphocyte’s DNA so all clonal offspring have the same DNA At any given time, 108 different specificities can be observed in circulating lymphocytes = lymphocyte receptor repertoire Remember, only cells that experience their antigen will differentiate into effector cells BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Lymphocyte development Clonal selection then clonal expansion What about errors? Clonal deletion If lymphocyte receives too much or too little signal through antigen receptor during development, they are targeted for apoptosis BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Lymphocyte development Lymphocytes mature in bone marrow (B) or thymus (T) Circulate in blood and lymph Congregate in lymphoid tissues or lymphoid organs Organized aggregates of lymphocytes in a framework of nonlymphoid cells Central or primary lymphoid organs Generate lymphocytes: bone marrow and thymus Peripheral or secondary lymphoid organs Mature naïve lymphocytes are maintained and adaptive response initiated Lymph nodes, spleen, mucosal lymphoid of gut, nasal and resp, urogenital, etc. BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Innate and Adaptive Interact Adaptive immune cells become effector cells IF appropriate inflammatory signals support activation T-cell example: dendritic cell picks up antigen and migrates to secondary lymphoid Dendritic cells are activated by? Activation also triggers dendritic cells to express co-stimulatory molecules to support T-cell development Engulf bacteria and viral particles, process it, present via MHC = antigen-presenting cells BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Lymphocyte activation Macrophages and B cells can also act as antigen presenting cells but dendritic cells are the specialists Free antigens can also stimulate BCR but most B cells require Th for optimal antibody response Activation of naïve T-cells is essential for most adaptive responses BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Lymphatic System Antigen-lymphocyte interaction typically occurs in secondary lymphatic tissue Nodes, spleen, mucosal, etc. Dendritic cells carry to these tissues then are trapped Mature naïve lymphocytes continuously circulated through lymphatic tissue. BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Lymphatic system Infection occurs, free antigen and antigen-bearing dendritic cells travel from infection site to lymph node via AFFERENT lymphatic vessels. Activate naïve lymphocytes Effector lymphocytes leave nodes via EFFERENT lymphatic vessel. Return to blood stream and to tissue where they will act BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Lymph Node Highly organized lymphoid organs at points of convergence of vessels of the lymphatic system (remember collects extracellular fluid and returns it to blood) Lymph flows away from peripheral tissues via lymphatics (lymphatic vessels) One-way valves prevent backflow Afferent lymphatics drain tissues Chemokines facilitate dendritic cell migration Chemokines also recruit lymphocytes which enter from blood through high endothelial venules (HEVs) BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Lymph Nodes Medulla and cortex B lymphocytes are in follicles composing the outer cortex T cells diffusely distributed in paracortical areas (deep cortex or T-cell zones) Lymphocytes enter paracortical area first as does lymph containing dendritic cells and free antigen = facilitation of T-cell interaction with antigen Some B-cell follicles = germinal centers where B-cells undergoing intense proliferation and differentiation BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Spleen Lymphocytes enter and exit via BLOOD Disposes of RBC Contains zones of T-cells and B-cells Marinal zone B-cells rapidly produce antibodies with low affinity to bacterial polysaccharides Blood-borne microbes, soluble antigens, and antigen:antibody complexes are filtered BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Mucosal Mucosal-associated lymphoid tissues (MALT) Gut-associated lymphoid tissues (GALT); includes tonsils, adenoids, appendix, and Peyer’s patches Nasal-associated lymphoid tissue NALT Bronchus-associated lymphoid tissue (BALT) Many of these contain M cells (microfold): specialized epithelial cells that collect antigen BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu  Lymphocytes continued and Start Innate BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Effector Mechanisms Effector mechanism must be tailored to individual pathogen Defenses against different pathogen types are organized into effector modules based Tell and humoral mechanisms, both innate and Collection of cell-mediated me adaptive, that coordinate to combat a pathogen BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Antibodies Protect against pathogens AND toxic products rattlesnakevaccineagainstvenom Found in plasma and extracellular fluids Body fluids once known as humors: antibodies known as humoral immunity 5 forms of the constant region of an antibody Classes or isotypes Determines functional properties BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu  Antibodies binds Bind to pathogens and block access to cells = Neutralization Abiobdhgdsrectf.la Many bacteria can still replicate despite antibody binding and evade phagocytes because of outer coat. Antibodies bind outer coat and Fc receptors on phagocytes bind constant region to facilitate phagocytosis. A Coating of pathogens = Opsonization Function to activate complement system complement systemactivated to lyse RBC CH50Assay BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu  bindstopathogen BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu T Cells 9 Facilitate removal of intercellular pathogens Cell-mediated immunity of adaptive immune response Where do T-cells develop? thymus Characterized by type of T-cell receptor 2 main classes CD8 or CD4 (CD = cluster of differentiation) CD4 and CD8 function in antigen recognition by recognizing different regions of MHC molecules then coordinating T-cell response = coreceptors T cellssignal high cytokinestorm BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu  T-cells MHC class I and MHC class II Peptides trapped in elongated groove (internal) then peptide:MHC complex translocates to cell membrane. CD8 recognizes MHC class I CD4 recognizes MHC class II different immune cells have differentgeneexpression profiles more T cells w CD4 than CD8 way samplefrom have to use flow cytometry to sort profiles changeso after fast taking animal BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu T-cells activated Cytotoxic T-cells: effector cells that directly kill infected cell CD8/MHC class I CD4 T-cells recognize MHC class II which is common on antigen presenting cells (dendritic cells, macrophages, and B-cells) Recognize pathogens taken up by phagocytosis Largely compose T-helper cells (Th) which drive cytokine profiles In lymphoid tissue T follicular helper (TFH) interact with B cells to regulate antibody production killedvaccinesdont stimulate T cells v much BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu  throughcytokines BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu  College of Agricultural, Consumer and Environmental Sciences BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Innate Immunity BE BOLD. Shape the Future. The College of Agricultural, Consumer and Environmental Sciences is an engine for economic and community development New Mexico State University aces.nmsu.edu in New Mexico, improving the lives of New Mexicans through academic, research, and Extension programs.  nonspecific firstline ofdefense barrierfails gainimElites there is no response BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu  mostchallengedline ofdefense animalsresponse sometimesworse thedisease 15h BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu  Pathogenic mechanism codes viralgenome something thecauses theproblem cytopathetic effectscan change wenvironment BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu 1st Barrier: Epithelial Surfaces Epithelial cells held together by tight junctions Internal epithelial are mucosal epithelia that secrete...? washe Contains glycoproteins that contain mucins coatbacteria soapcoatsbacteria themaway Coat bacteria Peristalsis and other mechanical movements prevent attachment Presence of commensal bacteria goodbacteria Epithelial cells can also produce antimicrobial proteins and chemical barriers (digestive enzymes, bile salts, fatty acids, etc.) BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu 1st Barrier: Epithelial Surfaces Antimicrobial Enzymesmast wilddogslickingtheirwounds Lysozyme: tears, saliva, and phaygocytes Breaks down peptidoglycan in bacterial cell wall Antimicrobial Peptides Defensins, cathelicidins, histatins Short peptides around 30 to 40 amino acids Disrupt cell membranes of bacteria and fungi and the cell envelope of some viruses Thought to create pores in membrane that can contribute to pathogen drought littlewater dustdisrupts these barriers invasion BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu 1st Barrier: Epithelial Surfaces Carbohydrate-binding proteins Called Lectins C-type lectins require Ca for carbohydrate-recognition domain Bind peptidoglycan on bacteria and elicit bactericidal effect provides another layerof protection BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Complement System After breaching epithelial defenses, next major defense is complement system Composed of more than 30 different proteins produced mainly by liver Circulate in inactive form oncecompi Interaction with pathogen or antibody-coated pathogen activates protein 3 pathways of complement activation 95 Classical: Antibody-triggered activation Alternate: Activated by pathogen alone 1 Lectin: activated by lectin-type proteins BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Complement System Proteolysis: means of activation of antimicrobial proteins. Digests proteins to their active form In complement system, activation by proteolysis is inherent where complement proteins successively cleave and activate one another Proteases of compliment system are synthesized as inactive pro- enzymes (zymogens) and are activated by proteolytic cleavage 3 main methods to address pathogen Inflammation Phagocytosis Membrane Attack 1st cleaves itself leads toactivationof others BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu ordedby howthey are in cascade  indivic orcleavageproducts proteins oink cEffinger  College of Agricultural, Consumer and Environmental Sciences BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu Induced Responses of Innate Immunity BE BOLD. Shape the Future. The College of Agricultural, Consumer and Environmental Sciences is an engine for economic and community development New Mexico State University aces.nmsu.edu in New Mexico, improving the lives of New Mexicans through academic, research, and Extension programs.  swineindustryhaveselectedawayfromimmuneresponse notexposed atall verysusceptibletodisease Innate proinflammatory cytokines biosecurity heavy purveyfor pathogens Produced mainly by tissue macrophages and dendritic cells Mast cells, endothelial cells, and some epithelial cells produce them fomm.toneighbor Most act paracrine; sever cases systemic level rise (endocrine) Consider that relative to animal science Serve several roles Induce inflammation goodthing bewewant to getrid ofthe pathogen Inhibit viral replication Promote T-cell response THI4THZ cytokine profile differentiates them Limit innate response Many cytokines are produced by T-lymphocytes as well (IL17, IL5, IFN- gamma, TNF etc.) BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu TNF-alpha Produced primarily by macrophages and dendritic cells Two receptors TNF-RI and TNF-RII Both are typically present on cells Exist as trimers in membrane bot involvedin Depending on signal, can induce apoptosis or induce gene transcription Stimulated by PAMPs and DAMPs (think TLRs, NLRs, etc.) Contributor to autoimmune/inflammatory diseases arthritistreatment piffers High levels can be secreted toofar where response is worse thaninfection BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu  joints arthritis in BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu IL-1 Major source is activated phagocytic mononuclear cells (local/systemic) Also produced by neutrophils, epithelial cells, and endothelial cells IL-1 alpha and IL-1 beta Less than 30% homology but bind same receptor and same activities Main form secreted in infection is IL-1 beta Induced by TLR and NLR; also by TNF action on phagocytes and other cells Type I IL-I receptor (endothelial, epithelial, leukocytes) Type IIRec is decoy modeofregulation hormone regulationitself or canbind up 14 effect totalcontrol of 121 BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu  Nod-like receptor family, pyrin domain containing 3 NLRP3 Apoptosis-associated Speck-like protein containing a CARD Caspase activation and recruitment domain 9third Inflammasome processes precursors for IL-1B and IL-18 form converstate BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu  IL Cannon alarge varietyo Impacts BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu IL-6 Local and systemic effects Induces synthesis of acute phase proteins Stimulates neutrophil production Promotes differentiation of IL-17 producing Th cells Synthesized by mononuclear phagocytes, DCs, vascular endothelial cells, fibroblasts, and other cells PAMPs, IL-I, and TNF can drive production BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu  suppresides enny are BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu  are is m iE made BE BOLD. Shape the Future. New Mexico State University aces.nmsu.edu immune system interaction w in AP limitsgrowth performance due to cytokine intersection  fever shiveringso it is energycostly using alot ofAA  PABJstem highblood glucose if too far some bacteria thrive in high glucose levels  immunecells have the glucose to work environment but some bacteria thrive in highglucose PI W BVD calves have inflammation I dont grow very well Heat and Cold Immune Environmental Stress Heat stress occurs when heat dissipation mechanisms are overwhelmed, leading to hyperthermia and oxidative stress. Cold stress challenges homeotherms to maintain core body temperature, redirecting metabolic energy towards heat generation. Both types of stress can suppress immune function and impair disease resistance. rerouting bloodflow for heat coldstress Cellular and Molecular Responses to Heat Stress give dex to limit inflammation Heat stress occurs when the ambient temperature exceeds an animal’s thermo-neutral zone (TNZ), leading to elevated core temperatures. This activates the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic-adrenal-medullary (SAM) axis, causing increased secretion of cortisol and catecholamines cortisol is generate immune suppressor  cort.int atearlypregnancy didnt effect it Glucocorticoid Pathway and Immune Suppression The HPA axis leads to the release of glucocorticoids (primarily steroid cortisol). These hormones bind to glucocorticoid receptors (GR) on immune cells, affecting gene expression by interacting with Internal of NF-κB and inhibiting pro-inflammatory cytokines such as TNF- cell α, IL-6, and IL-12 This shifts immune response from cell-mediated immunity (Th1) towards humoral immunity (Th2), leading to weakened defense against pathogens heatstress upregulates pro inflammatory cytokines whatglucocorticoids arethought to do to the beaves Eiii block 14,6 TN FX general immune suppression  upggten.tt t0 pathway NF-κB Pathway Tredrivepointcytolane Heat stress activates the NF-κB pathway, primarily through toll-like receptor 4 (TLR4). 1,1Yates Under stress, TLR4 binds to MyD88, initiating the phosphorylation cascade involving IRAK, TRAF6, and TAK1, which eventually activates the NF-κB complex. Activated NF-κB translocates to the nucleus and promotes transcription of pro-inflammatory cytokines 1cytokines MAPK Pathway Mitogen-activated protein kinases (MAPKs), including ERK1/2, JNK, and p38, are activated by heat stress. These kinases regulate the production of cytokines and heat shock proteins (HSPs), which play a critical role in protecting cells from oxidative damage during hyperthermia MADKS HSP TLR4 Heat-Induced Oxidative Stress Heat stress increases the production of reactive oxygen can modulate species (ROS) in mitochondria. Elevated ROS levels lead immune n to oxidative stress, which exacerbates tissue damage and causemore suppresses immune function. ROS can activate redox- tissuedamage sensitive transcription factors like NF-κB and AP-1 exacerbated DAMPS release ROS drives NF KB pathway  Dairy cattle are particularly vulnerable to heat stress because of their ton of heatprod.be high metabolic heat production during lactation. This affects immune of lactation function by reducing dry matter intake (DMI) and increasing DMI susceptibility to mastitis and other infections susceptible todisease Heat stress also disrupts the intestinal barrier, allowing endotoxins (e.g., LPS) to enter the bloodstream, triggering systemic inflammation. This involves an infiltration of macrophages into the gut and activation of TLR signaling, further impairing immunity  Koch, et al. 2019 leaksthroughtightjunctions 99 Titons HScanshiftto move balancebetweenthese humoral response  Other General Physiological Outcomes willalterthe Productionwhether It is put or down dependent on situation biphasicrespons cyokineeffects todecreasemusclegrowth cytokinestorm limitstheir growth multipletreatments Pilfeance 50 lbs less than otherhealthy peers can get them there but will take longer a cytokines aregoingto shiftthese processes leukocytes all immunecells  WE When we break down to diff populations we see diff  virus in a want THI towork Activation of the Hypothalamic- Pituitary-Adrenal (HPA) Axis Dogma butexp conditions can makeoutgoother way Heat stress triggers the HPA axis, releasing cortisol. Suppresses immune responses by shifting from Th1 (cell-mediated) immunity to Th2 (humoral) immunity, reducing the effectiveness of immune cells like cytotoxic T cells, macrophages, and natural killer (NK) cells This decreases the body’s ability to fight infections takesawhilefor Abtogetgoing torpatheemiegeem't Inhibition of pro-inflammatory cytokines like TNF-α, IL-6, and IFN-γ. Lower production of reactive T cells, macrophages, and neutrophils Heat stress increases reactive oxygen species (ROS) and reduces the activity of antioxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase ROS can damage tissues and lead to systemic inflammation. Humoral Shift The shift toward Th2-mediated humoral immunity results in: Increased antibody production by B cells but reduced cellular response to pathogens. Weaker resistance to intracellular pathogens (viruses, certain bacteria) shift away allows virus to have an effect Reduced Cytokine Production Cold stress reduces the production of key cytokines like IL-2 and IgA, weakening the adaptive immune response. This means lower immune surveillance and increased susceptibility to infections Cold stress elevates TNF-α levels, leading to chronic inflammation and tissue damage howdoyoudiff effect of TNFα from effect of decreasedenergy Growth Hormone (GH) and Its Interactions with Immune Function Heat stress leads to a suppression of GH secretion. This occurs due to the HPA axis activation, which increases cortisol production and leads to a shift in metabolic priorities (favoring thermoregulation and energy conservation over growth and reproduction) Immune Suppression: Growth hormone has immunomodulatory effects, stimulating the proliferation of T cells and enhancing macrophage function. Under heat stress, reduced GH levels impair the adaptive immune response, resulting in fewer effective cytotoxic T cells and B cells Oxidative Stress and GH: Heat stress increases ROS levels, which, in turn, can inhibit GH secretion by inducing oxidative damage in GH-producing cells in the pituitary gland. This further exacerbates immune suppression The reduction in GH under heat stress leads to impaired growth, reduced lean muscle mass, and weakened immune function due to reduced T-cell and macrophage activity. theoretic idea in livestock asseen in rodent Insulin and Immune Function Under Stress Heat stress induces insulin resistance. This is due to elevated cortisol levels, which impair insulin signaling pathways. As a result, glucose uptake by tissues, particularly muscles, is reduced Immune and Metabolic Dysfunction: Insulin plays an important role in immune cell metabolism by facilitating glucose uptake. Immune cells such as macrophages and lymphocytes require glucose for energy, and insulin resistance impairs their function. Insulin and Inflammation: Heat stress also promotes the release of pro-inflammatory cytokines (e.g., IL-6, TNF-α), which further exacerbate insulin resistance. This creates a feedback loop where metabolic dysfunction feeds into immune dysfunction, and vice versa. Physiological Outcome: Insulin resistance leads to compromised immune cell function, reducing the effectiveness of macrophages, neutrophils, and T cells in combating infections. inhibit theirability touptake glucose I reducetheirabilityto fightinf  Insulin-like Growth Factor 1 (IGF-1) is 8 tod afterenteringfeedlot IGFI super low Heat stress reduces IGF-1 levels, primarily due to decreased GH secretion. IGF-1 is critical for stimulating cell proliferation, differentiation, and survival in both muscle and immune cells Immune Function: IGF-1 enhances the function of T cells, macrophages, and B cells by promoting cell proliferation and survival. A reduction in IGF-1 under heat stress leads to impaired immune cell proliferation and reduced immune surveillance ROS and IGF-1: Heat stress increases oxidative stress, which negatively impacts IGF-1 receptor signaling pathways. This further diminishes the ability of IGF-1 to support immune cell activity and muscle growth. Physiological Outcome: Lower IGF-1 levels under heat stress contribute to reduced immune cell function, weaker growth performance, and impaired overall health. environmental conditions effect IGF levels t t impactimmunefxntofhf.tt Vialard and Olivier, 2020 Lulu Shi, et al. 2022 indefeaxedos outdofen indeed