Adrenal Gland. MEDULLA Epinephrine CORTEX. Zona reticularis --adrenal androgen. Zona fasciculata --glucocorticoids

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1 STRESS AND IMMUNITY

2 STRESS Defined as life under tension Homeostatic range: normal physiological balance Stressors: physical and emotional stimuli that disrupt homeostasis Eustress vs Distress Stress response: a physiological and behavioral response to stressors

3 Adrenal Gland MEDULLA Epinephrine CORTEX Zona reticularis --adrenal androgen Zona fasciculata --glucocorticoids Zona glomerulosa --mineralcorticoids

4 Control of the Adrenal Cortex Hypothalamus CRF (corticotrophin releasing factor) Anterior Pituitary ACTH (adrenal corticotrophin hormone) Adrenal Cortex Cholesterol Progesterones Androgens Glucocorticoids Mineralcorticoids

5 Mineralocorticoids Aldosterone Maintains electrolytic balance Retains sodium in kidney; draws in water by osmosis Stimulus Dehydration Decrease in blood pressure Adrenalectomy Exogenous electrolytes

6 Glucocorticoids Corticosterone rodents and rabbits Cortisol hamsters, primates, cats, dogs Maintain blood glucose levels Increased levels required for physical activity Stimulus Circadian rhythm Physical or emotional stress

7 Glucocorticoid Rhythms in Nocturnal Animals Stress Glucocorticoid levels Food intake 6 am 6 pm Dark phase 6 am

8 Circannual glucocordicoid response Glucocordicoid levels are potentially higher in the winter due to increase stress of low temperatures and decreased availability of food Melatonin inhibits the adrenal gland response to ACTH to counteract this affect.

9 Adrenal gland mediated stress responses SAMS Sympathetic--adrenal medullary system First response Short term Defense Catecholamines Norepinephrine Epinephrine HPA Hypothalamus pituitary adrenal cortex axis Later response Long term Defeat Glucocorticoids Corticosterone Cortisol

10 SAMS STIMULI -exercise -physical stress -emotional stress BRAIN Adrenal medulla EPINEPHRINE -increase tidal volume in lungs -increase cardiac output -vasodilate vessels to heart and skeletal muscles -vasoconstrict abdominal vessels -decrease GI motility -increase conversion of glycogen to glucose

11 HPA Hypothalamus CRF Pituitary ACTH Adrenal Cortex Glucocorticoids Circulating blood Liver 1) converts glycogen to glucose 2) gluconeogenesis Skeletal muscle & adipose tissue Release amino acids & fatty acids Pancreas decreases insulin secretion

12 Acute Stress Causes Handling GC levels can double in 30 seconds Novelty Changing cages Enrichment Testing arenas Restraint devices Measurement Difficulties

13 Acute Stress Aggressive encounters Testosterone Corticosterone Fighting Behavior Dominant (winner) Subordinate (loser)

14 Chronic Stress Causes Pain Husbandry issues (ammonia, temperature, humidity, lighting, noise, vibration) Social issues (Housed alone, subordinate in hierarchy) Prolonged restraint Research manipulations

15 Chronic Stress Habituation Predictable or mild stress Hypothalamus CRF Pituitary ACTH Sensitization Unpredictable or strong stress Adrenal Cortex Glucocorticoids

16 Long-term effects of Elevated Glucocorticoids Break down of muscle and fat tissue Suppression of growth ( GH) Suppression of metabolism ( TRH, T 4, T 3 ) Suppression of reproduction ( GnRH, LH, PRL, T) Depressed immune function

17 Long-Term Effects of Elevated Glucocorticoids on the Immune System Inhibition of macrophage migration Decrease in phagocytosis Decrease in antibody production Atrophy of the thymus Net effect: Immunosuppression

18 Immune System Defense against invasion by bacteria, viruses, and parasitic pathogens. Components Physical barriers: skin and mucus membranes Blood and lymphatic vessels Leukocytes (White blood cells) Innate immune system: phagocytic and killer cells Adaptive immune system: lymphocytes and antibodies

19 Leukocytes (Do not need to memorize)

20 Granulocytes Neutrophils: Phagocytic plasma cell Major target: Bacteria Mechanism: When activated, they leak into infected tissues to attack, engulf, and neutralize bacteria. Major component of pus. Eosinophils: Major target: Parasites Mechanism: They secrete a chemical which can destroy organisms too large to engulf. They are also released during allergic reactions. Basophils & Mast cells They release histamines and heparin to increase blood flow to injured areas. Responsible for allergic reactions.

21 Monocytes Monocytesmacrophages: Target: Microorganisms, dead cells, and infected host cells Mechanism: Monocytes migrate into tissues where they become macrophages, or phagocytic tissue cells. They also upregulate other immune systems Cause neutrophils to leak into tissue Antigen presentation: present proteins from phagocytized organisms to T- cells to stimulate a specific immune response

22 Lymphocytes Both Formed in bone marrow Migrate to lymph tissue B-Lymphocytes Maturation site bone marrow Stimulus antigens Become Plasma B cells produce antibodies Memory B cells T-Lymphocytes Maturation site thymus Stimulus foreign cells Become Cytotoxic (natural killer) T cells Helper T cells Suppressor (regulator) T cells Memory T cells

23 Lymphocyte cascade (Do not need to memorize) Lymphocyte Stem Cell Antigen B memory cells B Lymphocyte + _ Cytokines Antibody Producing Plasma cells Helper T cells Regulator T cells T Lymphocyte Natural Killer T Cells (NKT) Foreign Cell Memory T cells Antibodies are released to mark antigens Destroys foreign cells

24 Antibody properties B-lymphocytes are stimulated by antigens, foreign molecules (protein, CHO, fat). Molecules can be free or attached to pathogenic cells. T cells are usually required to activate the B cell allowing for antibody production Once activated, antibodies can remain attached to B cells or can be released into the plasma as soluble antibodies. Binding of antibodies to an antigen causes 3 possible reactions Antibodies block pathogens from binding to or invading host cells Antibodies mark foreign cells for destruction by phagocytic cells Antibodies start an immune complement pathway to kill the cell

25 Antibody Classes IgM IgA IgE: IgD: Found in plasma & colostrum First responder to infection Low affinity and specificity High avidity Found in mucus membrane secretions of body orifices, GI tract, and milk First defense against invading pathogens Stimulate basophils and mast cells in response to allergens and parasites Found with IgM on naïve B cells. IgG Main form in circulation; found in plasma and colostrum Appears later in response to infection High specificity and affinity Low avidity Crosses placenta Crosses into extracellular spaces Increases following immunization or exposure Affinity: bond strength Avidity: bond stability

26 Primary vs. Secondary Antibody Response Primary Response first exposure Long lag Low antibody concentration Low antibody affinity Primarily IgM Short duration Production of memory B cells Secondary Response second exposure or exposure following vaccine Short lag High antibody concentration High antibody specificity and affinity Primarily IgG Prolonged duration

27 Diagnostic Techniques Antibody binding tests Binding of an test antigen to an antibody indicates previous exposure to that antigen. Can only test for specific antibodies; no general tests Takes 4 to 6 weeks for antibody titers to be high enough to register on serology tests. Positive result (symptomatic or sentinel animal): All animals within the barrier have been exposed (unless in IVC cages). Results are historical. Disease has had time to spread.

28 Research Applications Polyclonal antibodies Created by injecting antigens ID or SQ Collect blood. Isolate antiserum (serum will have multiple antibodies that bind to the same antigen). Monoclonal antibodies Created by binding an antibody-producing lymphocyte with an cancer cell line to form a fused cell called a hybridoma (immortalizing). Resulting cell is injected into the peritoneal cavity of an animal to produce an antibody that is specific not just to the antigen but to a single binding site on the antigen. Ascites fluid is collected from the abdomen to isolate the antibody Antibodies are used to identify and locate proteins Antibodies are made that are specific to a protein Antibodies are then bound to color-changing enzymes or florescent molecules Proteins can be found when antigen-antibody complexes are visualized

29 Immunocompromised Mice Used to study immunology, auto-immune diseases, oncology, transplantation Also used as sentinels Examples Athymic Fox1 nu nude mice Lack thymus so unable to produce T-cells SCID (Sever-compromised Immunodeficient) mice Genetic mutation affecting both B and T-cells NOD-scid Compromises the innate and adaptive immune system. Reduced NK cells and decreased levels of macrophage activation. NSG (NOD-scid IL2rg null) Mouse is completely deficient in the adaptive immunity and severely deficient in the innate immunity. Interleukin 2 is not expressed so cytokines cannot signal. Biosecurity level Gnotobiotic or axenic