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Immune System Overview
GOT DEFENSE?
ANATOMY OF THE IMMUNE SYSTEM
• The immune system
is localized in
several parts of the
body
– immune cells
develop in the
primary organs bone marrow and
thymus
– immune
responses occur
in the secondary
organs
IMMUNITY
Adaptive
Innate
Players
Humoral
•Macrophages
•Granulocytes
•Natural killer cells
•Complement
•Other chemicals
Characteristics
•Action is immediate; minutes to hours
•Response is nonspecific
•First line of defense against
invading pathogens
•Response is not enhanced on repeated
exposure to pathogen
Cell-Mediated
Players
•Antigen Presenting Cells
•T cells
•B cells
•Antibodies
Characteristics
•Action requires days to develop
•Response is specific
•Prevents progression to disease
•Response is enhanced on repeated
exposure to pathogen
Immune System: Innate and Adaptive
Cytokines
• Soluble protein molecules used by cells of the
immune system to communicate.
• Functions include:
– Mediation of natural immunity
– Regulation of lymphocyte activation, growth,
and differentiation
– Regulation of immune-mediated inflammation
– Stimulation of immature leukocyte growth and
differentiation
• Interleukins (IL-2 & IL-4), interferons ( ), tumor
necrosis factors ( and ), and transforming growth
factor 
Immune System: Innate and Adaptive
2. The immune system consists of:
Innate (non-specific)
immunity
•Anatomic barriers
(Skin,mucous membranes)
•Physiological barriers
(temperature, pH)
•Phagocytic Barriers (cells that
eat invaders)
•Inflammatory barriers (redness,
swelling, heat and pain)
Adaptive (specific)
immunity
Neutrophil
Eosinophil
Basophil
Monocytes
Dendritic cell
Immune System: Innate (phagocytosis)
1. Phagocytic cells: Macrophage,
Neutrophil, and Dendritic cells.
2. Phagocytosis serves two key functions:
•
Killing microbes
• Antigen (Ag) Presentation
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GOT DEFENSE?
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Immune System: Innate (phagocytosis)
Opsonization
Immune System: Innate
Inflammation
• A hallmark of innate immunity
• Local accumulation of immune cells and molecules against
•
microbes
Function to eliminate infections but often cause tissue
damage & diseases
Inflammatory Response
Inflammation
Inflammatory Response
The immune system consists of:
Innate (non-specific)
immunity
Adaptive (specific)
immunity
•Anatomic barriers
(Skin,mucous membranes)
•Antigen specificity
•Physological barriers
(temperature, pH)
•Phagocytic Barriers (cells that
eat invaders)
•Inflammatory barriers (redness,
swelling, heat and pain)
•Diversity
•Immunological memory
•Self/nonself recognition
Adaptive Immunity
Major Histocompatibility Complex (MHC)
•
•
•
•
•
Also known as Human Leukocyte
Antigen (HLA)
Membrane bound, not soluble
“Present” processed protein
antigens (peptides) to naïve T
cells
MHC I -> produced by almost all
nucleated cells, present antigen
to CD8+ cytotoxic T lymphocytes
(CTL)
MHC II -> produced by
“professional” antigen presenting
cells, present antigen to CD4+
lymphocytes (T helper cells)
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T Cell Receptors (TCRs)
•
•
•
•
•
•
Produced by T lymphocytes
Are surface bound, not
secreted
Recognize “processed”
peptide antigens presented
on MHC molecules
Heterodimer of  or 
chains
Like antibodies, each chain
has a variable and constant
region
Also undergo gene
rearrangement prior to
expression
The immune system has evolved to:
•Protect against invading pathogens or
foreign substances.
•Maintain tissue homeostasis.
•
Meanwhile, microbes have evolved to
survive in the host.