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Mellon/MCHS
Name:
Human Biology
Immunity/Immunology
Objectives:
1. Describe typical external barriers that ward off invading organisms
2. Understand the process of nonspecific inflammatory response
3. Understand how humans recognize and discriminate between self and
non-self tissues.
4. Distinguish between antibody-mediated and cell-mediated patterns of
warfare.
5. Describe some examples of immune failures and identify as
specifically as you can which weapons in the immunity arsenal failed
in each case.
Intro:
A. Jenner (1796) cowpox could protect against smallpox.
B. Pasteur (d.1896) vaccinations, pasteurization
C. Robert Koch: Discovered the cause of anthrax
I. Three Lines of Defense:
A. Pathogen: virus, bacteria, fungi, protozoa, parasitic worms that
cause disease.
B. Surface Barriers to Invasion
1. Intact skin and mucous membranes are barriers
2. Resident bacteria of mucous membranes such as intestine
and vagina deep pathogens in check by outcompeting
them.
3. Lysozymes: enzymes in the mucous membranes attack
bacteria and degrade their cell walls.
4. Enzymes in tears, saliva, and gastric fluid also degrade
pathogens.
5. Urine protects urinary tract (low pH)
C. Nonspecific and Specific response
1. Nonspecific: white blood cells, plasma proteins,
inflammation.
2. Specific: Mounted by lymphocytes, recognize unique
molecular configurations on invading pathogens.
II. Complement Proteins (C1)
A. 20 Proteins circulate in the blood and can be activated in two ways
1. Can bind to a complex of antibody/antigen
2. Can interact with carbohydrate molecules on the surfaces
of microorganisms.
B: CASCADE effect:
1. Membrane attack complexes become inserted into the
plasma membrane of pathogens causing lysis
2. Chemical gradients of proteins attract phagocytes to the
scene.
3. Complement proteins coat the surface of invading cells—
attracting phagocytes.
CQS
Comment/Question/Summary
Feel free to make a comment in
this box:
I rediscovered…
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This is important because…
Koch established the
bacterial cause of many
infectious diseases and
discovered the
microorganisms causing
anthrax (1876), wound
infections (1878),
tuberculosis (1882),
conjunctivitis (1883), cholera
(1884)
Mellon/MCHS
Name:
Human Biology
III. Inflammation
A. The roles of Macrophages and White Blood Cells
1. WBC arise from stem cells in bone marrow and can
circulate in the blood or reside in tissue.
2. Three types of WBC act swiftly but are not adapted for
sustained battles:
a. Neutrophils: ingest and digest bacteria
b. Eosinophils secrete enzymes that damage parasitic
worms; they also phagocytize foreign proteins and
help to control allergic responses.
c. Basophils secrete histamine, which alters blood
vessel permeability.
3. Macrophages (immature form is called monocyte) engulf
many foreign agents and do so repeatedly with a big
appetite.
B. The Inflammatory Response
1. Acute inflammation in a besieged tissue allows
phagocytes, complement proteins, and plasma proteins to
escape from the blood.
2. Physical signs include redness, swelling heat, and pain
3. The progression of inflammation is as follows:
a. Tissue irritation causes mast cells (a basophil) to
release histamine and other substances which
cause the blood vessels to become engorged and
capillary walls to become “leaky.”
b. Within a few hours, neutrophils and macrophages
leave the blood vessels to begin engulfing foreign
materials.
c. Macrophages release interleukin-1, which signals
other white blood cells, allows body temperature
to rise (further enhancing defense mechanisms)
and causes conservation of body energy due to
drowsiness.
d. Clotting mechanisms help wall off the pathogen
and promote repair of tissues.
Homework Assignment—on your own paper or in the CQS box:
1. What were Jenner, Pasteur, and Koch famous for?
2. List the Three Lines of Defense and describe how they work.
3. What are the four steps in the progression of inflammation?
4. Define the following terms: Complement proteins,
Neutrophils, Eosinophils Basophils, Macrophages
CQS
Comment/Question/Summary
Summarize the progression of
inflammation:
Mellon/MCHS
Name:
Human Biology
IV.
The Immune System
A. Defining features
1. Sometimes physical barriers and inflammation may not be
sufficient to overwhelm the invader.
a. Vertebrate immune system is a complex interaction of two
types of white blood cells called B and T lymphocytes.
b. This system displays both specificity and memory.
2. Each kind of cell, virus, or substance bears unique molecular
configurations that give it a unique identity.
a. Your own cells (self) bear surface proteins which your
lymphocytes ignore.
b. Nonself markers from viruses, bacteria, bee venom, organ
transplants, etc. bear antigens that trigger immune responses.
c. When B and T lymphocytes encounter a nonself marker,
they divide repeatedly.
1. Some become effector cells, which will engage and
destroy the enemy.
2. Others are memory cells that will be called upon later if
the invader strikes again.
3. Immunological memory and specificity involve three events:
a. recognition of a specific invader
b. repeated cell divisions to form huge populations of
lymphocytes
d. differentiation into subpopulations of specialized effector
and memory cells.
B. Antigen-Presenting Cells—Triggers for immune response
1. Any nonself marker that triggers the formation of
lymphocytes is an antigen; the antigen binding receptors
are antibodies, secreted by B cells.
2. MHC markers reside in the plasma membranes of body
cells; some are unique to your lymphocytes and
macrophages.
3. Macrophages can digest bacterial invaders but not their
antigens, which become attached to MHC molecules to
form antigen-MHC complexes
4. When antigen fragments and a certain MHC marker are
displayed together at the cell surface, lymphocytes respond
by dividing to produce huge numbers of lymphocytes.
C. Key Players:
1. Helper T cells produce and secrete chemicals that promote
formation of large populations of effector and memory cells.
2. Cytotoxic T cells kill body cells that have either become infected
with intracellular parasites or are identified as tumor cells. (cell
mediated immune response)
3. B cells are lymphocytes that produce antibodies. (antibody
mediated immune response.
CQS
Comment/Question/Summary
What does specificity and
memory mean ?
What is an antigen ?
Mellon/MCHS
Name:
Human Biology
D. Control of Immune Responses
1.When antibodies have "saturated" the binding sites on pathogens, fewer
exposed antigens translates into less production of antibodies.
2.Inhibitory signals from cells with suppressor functions shut down the
immune response.
V. Lymphocyte Battlegrounds
A. The antigen-presenting cells and lymphocytes interact in lymphoid
organs (tonsils, adenoids), lymph vessels, and lymph nodes.
B. In lymph nodes, cells are organized for maximum effectiveness with
antigen-presenting cells in the front line, engulfing invaders.
VI. Cell-Mediated Responses
A. T Cell Formation and Activation
1. T cells arise from stem cells in the bone marrow, then travel to the
thymus gland where they differentiate into helper T and cytotoxic T
cells and acquire receptors for MHC markers and antigen-specific
receptors.
2.Virgin T cells ignore both unadorned MHC markers and free
antigen but do bind antigenMHC complexes on presenting cells,
which stimulates division of the T cells to form clones.
B . Functions of Effector T Cells
1.Some clones, effector helper T cells, secrete interleukins that
stimulate cell divisions of virgin T cells and virgin B cells.
2.Effector cytotoxic T cells recognize MHC markers on viral-infected
cells and tumors and kill the cells by secreting perforins that punch
holes in the cell membranes.
C. Natural Killer Cells
1.Other cytotoxic cells such as natural killer (NK) cells also kill tumor
and infected cells.
2.They do not require an antigen-MHC encounter.
VII Antibody-Mediated Responses
A. B Cells and Targets of Antibodies
1. B cells also arise from stem cells and eventually produce copies
of a specific antibody.
a. Antibodies are proteins with binding sites for a single antigen.
b. The Y-shaped antibody is embedded in the B cell membrane
with the two arms extending as antigen receptors.
2. When its receptors lock onto an antigen, the B cell will undergo
repeated cell divisions IF there are also present secretions from a
helper T cell already activated by the same antigen.
3. The clonal B cells differentiate into effector (formerly known as
plasma) cells and memory cells; effector cells produce antibodies
that recognize antigens and mark their possessors for destruction by
phagocytes.
4. The main targets of antibody-mediated responses are extracellular
pathogens and toxins.
B . Immunoglobulins
1. All five classes of antibodies have binding sites for antigen but the ones in
each class have special sites for specific functions.
2. The different classes are the protein products of gene shufflings:
a.IgM antibodies set the complement cascade in motion and bind
invaders into dumps.
CQS
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I rediscovered…
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I find it interesting that…
I wonder…
This is important because…
Mellon/MCHS
Name:
Human Biology
b.IgG antibodies neutralize toxins, are long lasting, can cross the
placenta, and are found in mother's milk.
c.IgA antibodies are present in the mucus of respiratory, digestive,
and reproductive tracts.
d.IgE antibodies bind to basophils and mast cells where they act as
traps for antigen.
IX. Immune Specificity and Memory
A. Formation of Antigen-Specific Receptors
1. Immunological specificity lies in DNA recombinations.
a.All T and B cells have the same genes coding for the
polypeptides in each arm of the antibody molecule.
b.Many different polypeptides can be made by shuffling the genes
into millions of combinations to produce antibodies against
numerous agents.
2. The clonal selection theory proposes that a lymphocyte activated
by a specific antigen will divide and give rise to a clone of cells that
are specific only to that antigen.
B . Immunological Memory
1. Immunological memory of a primary immune response is
explained by the clonal selection theory.
2. Some B and T memory cells will continue to circulate for years
and make secondary response to any subsequent encounter of the
same antigen.
3. This later response will be more rapid, greater, and of longer
duration than was the primary immune response.
X. Immunization and Other Practical Applications of Immunology
A. Immunization
1. Immunization involves a deliberate production of an immune
response and memory cells.
a.In active immunization, the first dose of vaccine elicits a
primary immune response; a second dose ("booster") elicits a
secondary, and more long-lasting, response.
b.Passive immunization involves injections of antibodies to
persons already infected with pathogens.
2. A vaccine can be made from killed or weakened pathogens,
inactivated toxins, or genetically engineered viruses.
B . Monoclonal Antibodies
1. Monoclonal antibodies are obtained by techniques that produce
large quantities of antibody from B cells.
a.A mouse is immunized with a specific antigen; B cells are
extracted and fused with cancerous cells known as myeloma
cells to produce a hybridoma cells.
b.The hybridoma cells produce the desired antibody
indefinitely.
2.Monoclonal antibodies are being used commercially in home
pregnancy tests, screening for prostate cancer, and passive immunity.
C. Cytokines
1.Signaling molecules produced by lymphocytes are called
cytokines.
2.Tumor necrosis factor secreted by cytotoxic T cells has been used
experimentally to treat malignant melanoma of the skin.
3.Interferons have been used to suppress viral diseases.
CQS
Comment/Question/Summary
I rediscovered…
I learned…
I find it interesting that…
I wonder…
This is important because…