Transcript Week 2 Immunology

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
Questions and Answers
Ohio
Colorado
Washington State
Food Safety and High-Risk Groups
Adaptive Immunity
Adaptive Immunity
Humoral Immunity
B-cell and antibody
mediated response
Food Safety and High-Risk Groups
Cell Mediated Immunity
T-cell response
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
Cytokine
release (IL-4
and 5) from
helper T cell
activates B cell
CD4 Helper
T-cell
(TH2 type)
Plasma
cell
T-cell receptor
combines with
MHC II complex
Memory
B-cell
B-cell proliferation
Pathogen
Lymph Node
B-cell
Antigen presenting cell
MHC II complex formed
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
Ohio
Colorado
Washington State
Food Safety and High-Risk Groups
How do foodborne pathogens
invade the human body?
Food Safety and High-Risk Groups
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
Bacterial
exotoxin acts as
Superantigen
Massive
Ineffective
cytokine
CD4release
T-cell
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
Ohio
Colorado
Washington State
Food Safety and High-Risk Groups
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
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
Ohio
Colorado
Washington State
Food Safety and High-Risk Groups