Transcript Immune System - Mr. Mazza's BioResource

Immune System
Immune System
• System of chemicals, white blood cells,
and tissues that protect the body against
pathogens (disease causing
microorganisms)
• Immune system has non-specific and
specific responses
• Aided by lymphatic system
Lymphatic System
• Returns fluids leaked from
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the blood back to the blood
Contains many different
types of leukocytes involved
in the immune response
Lymphoid organs include:
lymph nodes, spleen,
thymus, tonsils, and lymphoid
tissue in digestive and
respiratory tracts
Lymph nodes filter lymph of
pathogens and activates
immune response against an
antigen
Lymph Node
White blood cells originate from stem
cells in red bone marrow
Lines of Defense Against Pathogens
Nonspecific system:
1st line of defense (surface membrane barriers):
- skin (keratin) and acid mantle (sweat, sebum)
- mucous membranes and secretions (saliva, tears, mucus,
stomach acid, enzymes, urine, earwax, nasal hairs, etc.)
2nd line of defense (cell and chemical defense):
- Phagocytes: white blood cells that “eat” foreign matter (ex.
Macrophages, dendritic cells)
- Natural killer cells (kill virus infected cells)
- chemicals released from cells and damaged tissues (interferon,
histamine, complement)
- Inflammation (attracts white blood cells to the area and
prevents spread of infection) and fever (speeds up the activity
of white blood cells and slows down viral replication)
Specific (Adaptive) System
(3rd line of defense)
• React against a specific antigen (cell membrane
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protein) on the surface of the pathogen.
Involves B-lymphocytes (humoral immunity) and
T-lymphocytes (cell-mediated immunity)
Also involves antigen-presenting cells (APC) like
macrophages and dendritic cells (ingest
pathogen and display the pathogen’s antigens on
their surfaces)
B-lymphocytes (B-cells)
• Type of lymphocyte involved in
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humoral immunity
Develop into plasma cells which
secrete antibodies when they
recognize an antigen
Antibodies are made against
specific antigens
Memory B cells are produced
after 1st exposure to antigen results in quicker response if the
person is exposed to the same
antigen again
Antibody binding to
antigen
Primary and Secondary
Immune Response
Memory cells
formed
Blood antibody
level rises more
quickly with
2nd exposure
T cells
• Type of lymphocyte involved in
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cell-mediated immunity
Cytotoxic T-cells (Tc) kill only cells
that are infected with a virus
Helper T-cells (Th) release
chemicals called cytokines to
activate B-cells, cytotoxic T-cells,
and macrophages
Suppressor T-cells (TS) slow down
activity of B and T cells once the
antigen has been destroyed
Helper T cell signaling B cell to
differentiate into plasma cell and
Memory T-cells cause quicker
produce antibodies
response if infection with same
pathogen occurs again
MHC Proteins
• Proteins on the surface of
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cells that identify a cell as
belonging to the organism
Class I MHC are found on
all body cells
Class II MHC are found
only on certain cells that
are part of the immune
response
MHC proteins are used to
display foreign antigens
for recognition by T and B
lymphocytes
Hypersensitivity (allergies)
• When the immune system overresponds to a
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harmless antigen causing tissue damage in
the process
Antigen stimulates overproduction of IgE
antibodies by B cells (plasma cells)
IgE antibodies attach to mast cells which
contain histamine
Histamine is released in mass quantities
when a second exposure to the antigen
occurs
Histamine causes the symptoms of allergies
Animation #4
Active vs. Passive Immunity
• Active - a person’s immune system forms
memory cells against an antigen (either
through contracting an illness or through a
vaccine)
• Passive - a person receives antibodies
against an antigen but does not form
memory cells
Each day, about 77 people get the organ transplant that gives
them a second chance, but 19 others die waiting for a
donated organ.
Tissue and Organ Transplants
• MHC antigens (HLA
antigens) are compared
to determine a match
between donor and
recipient
• Must be at least 6 MHC
antigens in common in
order to consider a
transplant
• Immunosuppressant
drugs must be given to
prevent a rejection
Inflammation and CV disease
• Some interleukins are released by
macrophages and endothelial arterial
cells
• IL-6 attracts white blood cells to eat
cholesterol deposited by LDL and burst
forming plaque