Download Document

I.
Nonspecific defences
A. Species resistance
B. Mechanical barriers (skin, mucous membranes, sweat,
sloughing epidermis) form the first line of defense.
C. Chemical barriers (along with D-G) form the second line of
defense.
1. Enzymes
2. Interferons are made by some virus infected cells. They
will bind to receptors on uninfected cells to block the
entrance of a variety of other viruses.
3. Defensins are made when non-self cells
are recognized. Some of them work by
poking holes in bacterial cell walls and
membranes.
4. Collectins recognize a variety of bacteria, yeast, and some
viruses. They grab onto them and hook them up together so
that they can be easily phagocytized.
D. Fever - Infection causes lymphocytes to make interleukin-1
that causes the body’s temperature set point to increase. This
causes the liver and spleen to hold onto iron, reducing its levels
in the blood. Without iron, bacteria and viruses reproduce
more slowly.
E. NATURAL KILLER CELLS (lymphocytes) provide protection
against some viruses and cancer by secreting PERFORINS that
disintegrate the cell membranes of infected cells. They also
speed up inflammation.
F. INFLAMMATION - localized redness, swelling, heat and pain
results from leaky blood vessels enabling white blood cells to
reach the site of infection.
G. Phagocytes engulf and destroy pathogens.
II. ANTIGENS are molecules (proteins,
sugars, glycoproteins, or glycolipids)
that extend from the surface of a
foreign cell to signal the body that
it doesn’t belong.
III. Specific defenses (adaptive) immunity
A. Lympocyte origins
1. During fetal development undifferentiated lymphocytes
are released into circulation by red bone marrow.
2. Lymphocytes that reach the thymus differentiate into
T-cells/T-lymphocytes.
3. B lymphocytes/B-cells differentiate in the red bone
marrow.
B. Lymphocyte functions
1. Cellular immune response/cell mediated immunity
a. T cells become activated by the presence of
ANTIGEN-PRESENTING CELLS (Macrophages and
B-cells that have processed antigens on their
surface).
b. HELPER T CELLS become activated when their
antigen receptors combine with foreign antigens.
Helper T cells stimulate B cells to make antibodies
for the antigens they present.
c. CYTOTOXIC T CELLS recognize nonself antigens from
cancerous or virus infected cells. When they bind to
antigens, they begin to make clones. Cytotoxic T cells
release PERFORIN that cuts holes in cells to destroy them.
d. MEMORY T CELLS are made upon initial exposure to an
antigen. They provide a no-delay response for future
exposure.
2. Humoral immune response
a. Some B cells can become activated from binding with
antigens that fit in their antigen receptors. Most B
cells need helper T cells to activate.
b. When activated helper T cells
encounter a B cell-antigen complex,
they release cytokine proteins that
stimulate the B cell to proliferate.
1. Cytokines can also be released to
inhibit B cell function.
c. Some activated B cells can differentiate into MEMORY
cells that can rapidly respond to subsequent exposure to
antigens.
d. PLASMA cells are differentiated B cells that produce
antibodies similar to antigen receptor molecules on the
original B cells surface. A single plasma B cell can only
produce one kind of antibody.
IV. Antibody actions
A.
Direct attack - antibodies cause antigens to clump so they
can easily be phagocytized.
B. COMPLEMENT - when certain antibodies bind, the release
compliment protein that acts in a variety of ways: making
antigens more susceptible to phagocytosis, attracting
macrophages and neutrophils, clumping, rupturing membranes
of foreign cells, altering the molecular structure of viruses
to make them harmless.
C. Prevent the spread of antigens
V.
Immune responses
A. A primary immune response will usually
produce detectable levels of antibodies
in the blood within 5 to 10 days
following infection.
B. Because of memory B cells, a secondary
immune response will usually produce detectable
levels of antibodies in the blood within 1 day.
VI. Classifications of immunity (worksheet)
V.
Allergies result form an immune attack on
non-harmful substances.
VI. Autoimmunity results when the immune
system fails to distinguish self from
non-self and the body attacks itself.