Week 2 Immunology Dr. Lydia Medeiros Food Safety and High-Risk Groups

Vocabulary of the Immune System Handout #1 Food Safety and High-Risk Groups

The Immune System Innate or Natural Immunity (vertebrates/invertebrates) –Nonspecific response –Immediate response –Short-term response Adaptive or Acquired Immunity (vertebrates) –Specific response –Slow response –Long-term response

Innate Immunity Skin Mucosal secretions Intestinal pH and digestive enzymes Peyer’s Patch in intestine (M cells) Reticuloendothelial System Involves Natural Killer cells, Complement and Phagocytic cells (neutrophils or macrophages)

The Reticuloendothelial System Blood and tissue phagocytic cells (neutrophils and macrophages) Lymphoid tissue Liver (Kupffer cells) Spleen (red pulp) Bone marrow Lung, lining of the GI tract, urogenital tract

Destruction of Bacteria by Phagocytosis and Complement Handout #2 Food Safety and High-Risk Groups

Cells of the Immune System Handout #3 Food Safety and High-Risk Groups

Cells of the Immune System B-cells –Derived from stem cells in the bone marrow –Late stage or mature B-cells released to circulation (maturity completed in spleen) –Naïve B-cells encounter antigen via antigen presenting cells or direct contact –Immune reactions involve lymphatic system, lymph nodes, and spleen (white pulp)

Cells of the Immune System T-Cells –Derived from stem cells in bone marrow –Immature T-cells transport to the thymus –Selectivity against self occurs in thymus –Only about 5% of nascent T-cells survive maturation in the thymus –Responds to MHC class I and class II complexes in periphery, especially lymphatic system and lymph nodes

Overview Summary First line of defense –Mechanical barriers –Chemical barriers Second line of defense –Inflammation response –Phagocytosis Third line of defense –Specific immune responses –Natural Killer Cells

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Adaptive Immunity Humoral Immunity B-cell and antibody mediated response Cell Mediated Immunity T-cell response Food Safety and High-Risk Groups

Adaptive Immunity Phagocytic cells (neutophils or macrophages) Thymus and lymphoid tissues B-cells and T-cells Food Safety and High-Risk Groups

Adaptive Immunity Antibody A protein that is produced as a result of the introduction of an antigen and has the ability to combine with the antigen that stimulated its production. Food Safety and High-Risk Groups

Adaptive Immunity Major Histocompatibility Complex (MHC) A cluster of genes located in close proximity that determine histocompatibility antigens from members of a species. (eg. recognition of self versus non-self). Food Safety and High-Risk Groups

Adaptive Immunity Cytokine A factor such as a lymphokine or monokine produced by cells that affect other cells (eg. lymphocytes and macrophages) and have multiple immunomodulating functions. Cytokines include interleukins and interferons. Food Safety and High-Risk Groups

Adaptive Immunity B-cells –naïve cells have not encountered antigen –antibody on cell surface binds antigen –antigen presenting cells –predominately require signal from T-cell for activation –after activation, plasma cells produce and secrete antibodies –some B-cells become memory cells

Adaptive Immunity T-cells –CD4 T-cells (Helper – TH1 or TH2) Recognized MHC class II complexes TH1 activates macrophages TH2 activates B-cells –CD8 T-cells (Cytotoxic or Killer T-cells) Recognizes MHC class I complexes Lyses infected cells

The Humoral Immune Response CD4 Helper T-cell (T H 2 type) Pathogen B-cell Cytokine release (IL-4 and 5) from helper T cell activates B cell Y Y T-cell receptor combines with MHC II complex T-cell receptor combines with MHC II complex B-cell proliferation Memory B-cell Plasma cell Y Y Y Y Antigen presenting cell MHC II complex formed Lymph Node

The Cell-Mediated Immune Response Antigen Presenting Cell CD4 Helper T-cell (T H 1 type) Pathogen CD8 Cytotoxic T-cell Cytokine release and interaction with CD8 cells

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How do foodborne pathogens invade the human body? Food Safety and High-Risk Groups

Viral Infections Norovirus and Hepatitis A Virus Antigen Presenting Cell ﻉ Virus produces protein Protein/MHC class I complex forms CD8 Cytoxic T- cell responds to MHC class I complex Natural Killer cell

Parasitic Infection Toxoplasmosis gondii Tissue cell Parasite

Parasitic Infection Toxoplasmosis gondii Cryptosporidium parvum ??? Macrophage CD4 Helper T-cell (T H 1 type) Parasite CD8 Cytotoxic T-cell Cytokine release and interaction with CD8 cells Y Y Y Y

Bacterial Intoxications (Exotoxin) Staphylococcus aureus Antigen Presenting Cell CD4 T-cell Bacterial exotoxin acts as Superantigen Massive cytokine release Ineffective CD4 T-cell Systemic Toxicity – Virulence factor Supressed Immune Response Human Host Becomes Sicker

Bacterial Infection Listeria monocytogenes Macrophage Macrophage Listeria Listeria infects another macrophage No Immune Response

Bacterial Infection Listeria, Campylobacter, V. parahaemolyticus, Yersinia Antigen Presenting Cell CD4 Helper T-cell (T H 1 type) Pathogen CD8 Cytotoxic T-cell Cytokine release and interaction with CD8 cells

Toxin-Mediated Infections Salmonella, Shigella, E. coli O157, C. perfringens, B. cereus Toxin –Produced systemically or intra-luminally –Toxin neutralized by antibodies and complement Infective cells –Neutralized by immune response

Toxin-mediated Infection Bacteria grow Produce toxin Y Y Y Y Y Y C C C C C C C Y Y Toxin opsonized by antibody and complement Phagocytosis by APC

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The Immune System and Groups at High Risk for Foodborne Illness Infants and Young Children Pregnancy Seniors Immune Compromised Food Safety and High-Risk Groups

Infants and Young Children Immune defect –Immature immune system response –Lower infective dose

Pregnancy Immune Defect –Hormonal suppression of cell-mediated immunity –Switch from TH1 or TH2 T-cell type that favors antibody response –Listeria and Toxoplasmosis response specific for TH1 type T-cells

Listeria : Mode of Infection Pregnancy Listeria Helper T-cell (Th-2 type) Humoral Immune Response (Antibodies Produced) Listeria infects another macrophage

The Elderly Immune Defect –Decrease stomach acidity naturally –Increased use of anti-acid, anti-inflammatory or steroid medications –Decline in immune system response due to aging –Nutritional influence on immune response –Greater chance for exacerbating acute or chronic disease

Immune Compromised Status Pharmacological Immune defect Cancer - Loss of immune response efficiency due to disease or medical therapy Bone marrow transplant – Major reduction of immune system function due to absence and function of bone marrow Solid organ transplant – Mild suppression due to life- long use of immune suppressant drugs to prevent graft rejection.

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