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Immunology
Immunity – First Line of Defense
(Keeping pathogens from getting in)
• Skin and mucous membranes
– Epithelium traps pathogen – swallow or
expel them from the body
– Secrete oil and sweat – kills pathogens
with a pH of 3-5
– Lysozyme is produced by eyes and
upper respiratory tract – digests cell
walls so kills bacteria
Immunity – Internal
White Blood Cells/Proteins
Non-Specific
• Cells (develop in bone
marrow)
– Neutrophils
– Eosinophils
– Basophils
– Moncytes
– Natural Killer Cells
• Proteins
Specific
• B-cells
– originate from bone marrow
– Make anti-bodies – destroy
soluble pathogens
• T-cells
– Originate in bone marrow
and then go to thymus
– T-killer – kill tumor cells
and infected cells
– T-helper – activate T and B
cells
Non-Specific Immunity
• Quick, short-lived, activated specific
immunity
• Activated by damaged cells releasing
chemical attractants or break in skin
• Limits the spread of pathogens
Non-Specific Immune Cells
• Neutrophils ( 60-70% of WBC’s) First
responders
– Enter tissue, phagocytize invaders, die in the process
• Monocytes ( 5% of WBC’s)
– Enter tissue, become macrophages (lg. phagocytes),
kills cells by NO, reactive oxygen, and digestive
enyzmes in their lysosomes
– Releases cytokines to attract other immune cells
– Later act as APC’s (antigen presenting cells) to
specific immune cells
Non-Specific Cells continued
• Eosinophils (1.5% of WBC’s) – release
granules of enzymes to kill parasites
• Natural Killer Cells – destroy infected cells
and tumor cells by breaking open their cell
membranes with a secreted enyzme
• Basophils and Mast Cells – release
histamine in response to physical damage
or damage by microorganisms – Causes
an inflammatory response
Inflammation
• Histamine increases blood flow to an area by
dilating the pre-capillary arteries and constricting
the venules
• Increases the permeability of bv so immune cells
can get into the tissue
• Blood leaks into the area causing redness and
swelling
• Clotting factors activate and complement attracts
macrophages
• Pus – dead WBC’s and fluid leaked from the bv.
• Widespread inflammation – causes low blood
pressure and high fever (some inflammatory
cells release pyrogens that reset the brain’s
thermostat) – can die of septic shock
Non-Specific Immunity - Proteins
• Chemokines or Cytokines – released from
damaged cells or other immune cells
– Bind to receptors on immune cells – attract
them to the area or activate them
– Cause neutrophils to be released from the
bone marrow
– Cause monocytes to produce NO
– Cause basophils to produce histamine
– Etc.
Proteins Continued
• Complement – 20 proteins (both specific and
non-specific)
– Non-specific – attracts phagocytes, coats bacteria
making it easier to phagocytize, binds to basophils
and mast cells causing release of histamine and
inflammation
– Specific - Binds to 2 Ab bond to antigen and causes
lysis of invaders
• Interferon – produced by virus infected cells –
makes nearby cells resistant to virus infection
• Interleukins – activate other immune cells
Specific Immunity
Uses Specific Antigens
• Activity Immunity – your own immune
system responds
• Pasive Immunity – transfer of antibodies
– Rabies Treatment
– Mother’s Milk
• Humoral – antibodies (proteins) – can only
attack free pathogens in the blood
• Cell Mediated – can only attack cells
infected with pathogens and cancer cells
General Information about
Specific Cell Mediated Immunity
• Primary response – takes 5-10 days for a maximum
response against a specific antigen
• Secondary response – takes 3-5 days for a maximum
response (due to memory cells which divide faster and
survive longer)
• What happens when a T helper cells binds to an antigen
on an APC? The cell makes cytokines that cause
specific T killer and B cells to multiply
• What happens when a B cell binds to an antigen on a
free pathogen? B cell secretes soluble antibodies and
undergoes mitosis to make more of that B cell
• What happens when a T killer cells binds to an antigen
on an infected? It makes clones of the T cell and
secretes perforin to kill the infected cell
MHC
• MHC = major histocompatibility complex
• Marker proteins on the cell’s surface for
immune recognition
• 200 MHC molecules
• Class I MHC – on all cells
• Class 2 MHC – on macrophages, B and T
cells
• T - Helper cells
T cells
– CD4 cells (part of receptor)
– Recognizes antigen and MHC class II (APC’s)
– When binds to APC, makes cytokines that act on B and T cells (causes
them to multiply and activate)
• T – Killer cells (cytotoxic T cells) – Steps of
Activation
1. Pathogen is eaten by a macrophage (Antigen Presenting Cell or
APC)
2. APC digests the pathogen and displays antigens on MHC class II
3. T-helper binds and get activated – makes cytokines to activate T
killer cells – only activates T killer as shown below
4. CD8 cells (part of receptor)
– Recognizes infected or cancerous cells because they are displaying
antigen on MHC class I (binds to the infected cells)
– Releases enzymes that punch holes in the infected cell’s membrane
– Cell explodes releasing pathogens
– Pathogen no longer has a place to reproduce – antibodies pick it up or
macrophages eat it
Immunology You Tube Video
Infected Cell
B cells
• Has antibodies embedded in membrane as receptors /
secretes Ab in soluble form when activated
Steps of B cell activation
• Pathogen is eaten by a macrophage (Antigen Presenting
Cell or APC)
• APC digests the pathogen and displays antigens on
MHC class II
• T-helper binds and get activated – makes cytokines to
activate B cells
• B cells bind to antigens on free pathogens that match the
shape of their receptor (membrane antibodies)
• Only the B cells that bind to antigen get activated by the
cytokines – become plasma cells (make 2000 Ab/sec
and memory cells (can multiply faster the second time)
Antibody Structure
Variable Region makes
different 3-D binding
sites
It is made up of three
differerent regions:
Variable region – 400
different choices
Diverse region – 15
different choices
Joining region – 4
different choices
1 billion different
shaped antibodies
B cells also
become APC’s
when activated
and further
activate T
helpers which
produce more
cytokines to
activate the B
cells more
Antibody Functions
• Bind to antigen (neutralization) – may block the
activity (block virus from binding to a host cell,
etc.)
• Clumping or coating bacteria (opsonization) –
makes it easier for macrophage to engulf
• Activates complement which punches holes in
the cell membrane of bacteria