Principles of Immunology Prince Agri-Products & Phibro Animal Health Training Seminar – Atlanta, Georgia July 17-18, 2006

Immunity: security against a particular disease; nonsusceptibility to the invasive or pathogenic effects of foreign microorganisms or the toxic effect of antigenic substances.  Innate Immune System: consists of physical, chemical, enzymatic barriers and activity of phagocytic cells (neutrophils) which are associated w/ a signaling system  Adaptive (antibody- mediated) Immune System: consists of two components Humoral (antibody production in response to antigen, medicated by B-lymphocytes) Cell-mediated (production of specific killer cells in response to an antigen, mediated by T- lymphocytes)

Innate Immune Response - Neutrophils, first line of defense Phagocytes: first to arrive at the site of infection Function to contain infections, provide time for adaptive system to develop 200 billion in adult cow, 50% in circulation, remainder in bone or attached to vessel walls Life span of 1-2 days Contain a protein component: L-Selectin, index of innate immunity

Neutrophil recognition of pathogen Neutrophil Pathogen Pathogen-associated molecular Patterns: PAMPs) Receptors on surface of neutrophil

Phagocytosis Bacterium Recognition

Inactive neutrophils Activated neutrophils with NETs Source: Brinkmann et al., interleukin-8 (IL-8) Production of NETS by neutrophils

Association of neutrophil “NETs” with bacteria S. aureus (gram +) Salmonella (gram -) Shigella (gram -)

Neutrophils: a first line of defense - tethering via L-selectin (A) -shedding L-selectin (B) - Interleukin-1- pro- inflammatory (C) -migration toward “signals” (D) -phagocytosis (F) -pathogens Source: Burton and Erskine, 2003

Example of relationship between stress and immunity Cortisol - Adrenal hormone released in response to a stressful event needed by uterus at time of calving aids in intiating milk secretion by the mammary gland elevated blood Cortisol cause neutrophils to lose their ability to migrate from blood into tissue by interfering with L- selectin synthesis Source: Burton and Erskine, 2003

Cortisol Response Relative to Parturition Puntenney & French 2003

Effect of stress on neutrophils Normal Stress Proliferation and invasion of pathogens L-selectin and interleukin

Take home on neutrophils  First line of defense against bacteria and molds  L-selectin (tethering/rolling/ “surveillance”) (A/B)  IL-8 (signal from infection site) (D)  IL-1β (access infection site/ “diapedesis”) (C)  Free-flowing blood neutrophil (E)  Killing mechanisms (digestion and NETs) (F)

Pluripotent hematopoeitic stem cell (Self-renewing, white blood cell producing) Common lymphoid Progenitor (lymph tissue) Common myeloid Progenitor (bone marrow) B cells T cells NK cells White blood Red blood Megakaryocytes cells cells -Adaptive -Innate Monocyte Neutrophil Eosinophil Basophil Dendritic cell Macrophage Janeway et al., 2005 Platelets

Phases of an infection  1. Entry of pathogen  2. encounter a macrophage/dendritic cell  3. macrophage recruits neutrophils via IL-8  4. macrophage (phagocytic cell) and dendritic cells (antigen-presenting cells) migrate to lymph tissue where they encounter naïve B and T lymphocyte  5. B and T lymphocytes clonally expand and differentiate and make antibodies Innate Acquired

Linkage of innate and adaptive immunity  1. Activated macrophages and dendritic cells with ingested pathogen present antigen to T- lymphocytes  2. Chemokines, secreted by macrophages, enhance tissue permeability and influx of T- lymphocytes into an infection site (IL-1B)  3. Macrophages and neutrophils produce activating molecules (e.g., IL- 1β and IL-6) Activated neutrophil B and T lymphocytes IL-1β + Janeway et al., Activated T-cells, in turn, activate macrophages

Review  Terms Pathogen: disease-causing infectious agent Antigen: any molecule that stimulates the immune response (pathogen proteins or carbohydrates) Phagocytes: cells attracted to site of infection to destroy pathogens (not antigen-specific, part of innate system)  Neutrophils  Eosinophils  Monocytes/macrophages  Natural Killer Cells (virus-infected and cancer cells)

Review  Terms Leukocytes: white blood cells Adaptive Immunity: response to repeat infection  Synthesis of antibody to bind antigen and promote elimination  T cell killing of virus-infected cells  T cell activation of macrophages to destroy phagocytosed pathogens that are resistant to destruction

Review  Terms Innate Immunity: defense system that can recognize “generic danger” and responds by walling off and engulfing foreign organisms  Barriers - skin, mucous membranes  Mechanical – cilia, blinking, sneezing, coughing, vomiting  Chemical – HCl in stomach, digestive enzymes in tears, mucus  Phagocytes – Neutrophils, eosinophils, macrophages, M cells, monocytes  Natural Killer Cells – kill virus/cancer cells

Review  Terms Apoptosis: programmed cell death Macrophages: innate immune cell, binds pathogens, produce cytokines to attract other phagocytic cells and make blood vessels leaky, may present antigen to stimulate T cell activation (adaptive) Dendritic cells: innate immune cell, may be phagocytic and may present antigen to simulate T cell activation (adaptive immune system) Lymphocytes: antigen-specific white blood cells responsible for adaptive immunity

Review  Terms Natural Killer (NK) Cells: large lymphocytes that lack specific antigen receptors but respond to altered tissue typing in virus-infected and cancer cells Cytokines: small proteins produced by macrophages in response to bacterial antigens; signal other white blood cells; act by binding to specific membrane receptors to signal the cell to alter its behavior (gene expression)  Lymphokine (lymphocytes), monokine (monocytes), chemokine (chemotactic activity), interleukin (made by one leukocyte and acting on others)

Review  Terms Antibody: antigen receptor on B cells and is also secreted to bind and remove antigen from the body Immunoglobulins: antibodies that are antigen-binding proteins (IgG, IgM, IgD, IgA, IgE) Interleukin-1: cytokines produced by macrophages which activate nearby vascular endothelium to promote leukocyte movement into the tissue (extravasation) Interlukin – 8: chemokines which recruit leukocytes and attract them to site of infection L-selectin: neutrophil-adhesion molecule that initiates binding between leukocytes and endothelium