Week%202%20Immunology

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Week 2Immunology

• Dr. Lydia Medeiros

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

• Handout 1

Food Safety and High-Risk Groups
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The Immune System

• Innate or Natural Immunity (vertebrates/invertebra
  tes)
• Nonspecific response
• Immediate response
• Short-term response
• Adaptive or Acquired Immunity (vertebrates)
• Specific response
• Slow response
• Long-term response

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Innate Immunity

• Skin
• Mucosal secretions
• Intestinal pH and digestive enzymes
• Peyers Patch in intestine (M cells)
• Reticuloendothelial System
• Involves Natural Killer cells, Complement and
  Phagocytic cells (neutrophils or macrophages)

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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

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Destruction of Bacteria by Phagocytosis and
Complement

• Handout 2

Food Safety and High-Risk Groups
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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)

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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

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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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Questions and Answers

• Ohio
• Colorado
• Washington State

Food Safety and High-Risk Groups
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Adaptive Immunity
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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).

Food Safety and High-Risk Groups
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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.

Food Safety and High-Risk Groups
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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

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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

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The Humoral Immune Response
Y
Cytokine release (IL-4 and 5) from helper T cell
activates B cell
Y
CD4 Helper T-cell (TH2 type)
Y
Y
Plasma cell
T-cell receptor combines with MHC II complex
Memory B-cell

B-cell proliferation
Y
Y
B-cell
Pathogen
Antigen presenting cell MHC II complex formed
Lymph Node
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The Cell-Mediated Immune Response
CD4 Helper T-cell (TH1 type)
Cytokine release and interaction with CD8 cells
Antigen Presenting Cell
CD8 Cytotoxic T-cell
Pathogen
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Questions and Answers

• Ohio
• Colorado
• Washington State

Food Safety and High-Risk Groups
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How do foodborne pathogens invade the human body?
Food Safety and High-Risk Groups
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Viral InfectionsNorovirus and Hepatitis A
CD8 Cytoxic T-cell responds to MHC class I complex
Virus
Virus produces protein
Protein/MHC class I complex forms
?
Natural Killer cell
Antigen Presenting Cell
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Parasitic InfectionToxoplasmosis gondii
Tissue cell
Parasite
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Parasitic InfectionToxoplasmosis gondii
Cryptosporidium parvum ???
Cytokine release and interaction with CD8 cells
Macrophage
CD4 Helper T-cell (TH1 type)
Y
Y
Y
Y
CD8 Cytotoxic T-cell
Parasite
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Bacterial Intoxications (Exotoxin)Staphylococcus
aureus
Massive cytokine release
Ineffective CD4 T-cell
Bacterial exotoxin acts as Superantigen
Ineffective CD4 T-cell
Systemic Toxicity Virulence factor Supressed
Immune Response Human Host Becomes Sicker
CD4 T-cell
Antigen Presenting Cell
Ineffective CD4 T-cell
Ineffective CD4 T-cell
Massive cytokine release
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Bacterial InfectionListeria monocytogenes
Macrophage
Macrophage
Listeria infects another macrophage
No Immune Response
Listeria
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Bacterial InfectionListeria, Campylobacter, V.
parahaemolyticus, Yersinia
CD4 Helper T-cell (TH1 type)
Cytokine release and interaction with CD8 cells
Antigen Presenting Cell
CD8 Cytotoxic T-cell
Pathogen
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Toxin-Mediated InfectionsSalmonella, 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

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

• Ohio
• Colorado
• Washington State

Food Safety and High-Risk Groups
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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

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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

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

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Immune Compromised StatusPharmacological

• 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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Questions and Answers

• Ohio
• Colorado
• Washington State

Food Safety and High-Risk Groups