Week 2 Immunology
Dr. Lydia Medeiros
Food Safety and High-Risk Groups
Vocabulary of the Immune System
Handout #1
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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
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Cells of the Immune System
Handout #3
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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
Questions and Answers
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Adaptive Immunity
Adaptive Immunity
Humoral Immunity B-cell and antibody mediated response Cell Mediated Immunity T-cell response
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Adaptive Immunity
• Phagocytic cells (neutophils or macrophages) • Thymus and lymphoid tissues • B-cells and T-cells
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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.
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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).
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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.
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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 (TH2 type) T-cell receptor combines with MHC II complex Plasma cell Memory B-cell Cytokine release (IL-4 and 5) from helper T cell activates B cell
B-cell proliferation B-cell Antigen presenting cell MHC II complex formed
Pathogen
Lymph Node
The Cell-Mediated Immune Response
CD4 Helper T-cell (TH1 type)
Cytokine release and interaction with CD8 cells
Antigen Presenting Cell
Pathogen
CD8 Cytotoxic T-cell
Questions and Answers
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How do foodborne pathogens invade the human body?
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Viral Infections
Norovirus and Hepatitis A
CD8 Cytoxic Tcell responds to MHC class I complex
Virus
Virus produces protein
ﻉ
Natural Killer cell
Protein/MHC class I complex forms Antigen Presenting Cell
Parasitic Infection
Toxoplasmosis gondii
Tissue cell
Parasite
Parasitic Infection
Toxoplasmosis gondii Cryptosporidium parvum ???
Cytokine release and interaction with CD8 cells
Macrophage CD4 Helper T-cell (TH1 type)
Parasite
CD8 Cytotoxic T-cell
Bacterial Intoxications (Exotoxin)
Staphylococcus aureus
Massive Ineffective cytokine CD4 T-cell release Bacterial exotoxin acts as Superantigen
Ineffective CD4 T-cell Systemic Toxicity – Virulence factor CD4 Supressed Immune Response T-cell Human Host Becomes Sicker Antigen Presenting Cell Ineffective CD4 T-cell Ineffective Massive CD4 T-cell cytokine release
Bacterial Infection
Listeria monocytogenes
Macrophage Macrophage Listeria infects another macrophage
Listeria
No Immune Response
Bacterial Infection
Listeria, Campylobacter, V. parahaemolyticus, Yersinia
CD4 Helper T-cell (TH1 type)
Cytokine release and interaction with CD8 cells
Antigen Presenting Cell
Pathogen
CD8 Cytotoxic T-cell
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
Toxin opsonized by antibody and complement
Phagocytosis by APC
Questions and Answers
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The Immune System and Groups at High Risk for Foodborne Illness
Infants and Young Children Pregnancy Seniors Immune Compromised
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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
Helper T-cell (Th-2 type) Humoral Immune Response (Antibodies Produced)
Listeria
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 lifelong use of immune suppressant drugs to prevent graft rejection.
Questions and Answers
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