Vocabulary Passive Immunity- temporary immunity gained by
taking in anti-bodies or immune cells (lasts only a few weeks or
months) temporary because the system has been stimulated by
antigens Active immunity- immunity gained from recovering from an
infectious disease Acquired Immunity- when the body develops an
immunity for a specific pathogen by slowly building up a resistance
to it Primary Immune Response- selective proliferation and
differentiation of lymphocytes that occurs first time the body is
exposed to an antigen Secondary Immune Response- when the
individual is exposed to the some antigen at some later time, the
response is faster, of greater magnitude, and more prolonged
Humoral Immunity- involves B cell activation and results from the
production of antibodies that circulate in the blood plasma and
lymph, fluids that were long ago called humors Cell mediated
response- depends on the action of T-cells, immunity gained through
the transfer of humoral immunity (antibodies)
Slide 3
Nonspecific Defenses against Infection The skin and the mucous
both play their part as a physical barrier as well as a way to use
chemical defenses to counter pathogens In addition the secretions
from the sebaceous and sweat glands give the skin a pH between 3-5,
this pH is acidic enough to prevent colonization of microbes
Saliva, tears, and mucous are all secreted and constantly cover
exposed epithelia The lysozyme (protective protein) also helps by
digesting the cell walls of many bacteria thus destroying many
bacteria entering the upper respiratory tract and the opening
around the eyes Stomach contains a highly acidic environment, which
destroys most microbes before they enter the intestinal tract
(hepatitis A is a virus which can survive the gastric acids)
Phagocytosis- the ingestion of invading organisms by certain types
of cells (associated intimately with an effective inflammatory
response) Inflammation and phagocytosis help limit the spread of
microbes in advance for specific immune responses
Slide 4
Phagocytic and Natural Killer Cells Neutrophils are a class of
phagocytic cells that contribute to 60%-70% of all the white blood
cells in the body (while they do attack damaged cells and destroy
them, they tend to self destruct after killing off the damaged cell
and only have a normal life span of a few days Monocytes make up
only 5% of the white blood cells in your body but they are much
more effective, they circulate the blood for only a few hours then
migrate to tissues were they will become macrophages Macrophages-
largest phagocytic cells, are especially effective, live the
longest (engulf a microbe in a vacuole that then fuses with a
lysosome Lysosome then breaks it down in one of these two ways:
first it can make toxic versions of Oxygen; superoxide anion or
nitric oxide. The second version would be the use of lysosomal
enzymes to digest microbial components Although some microbes have
evolved and can avoid phagocytic destruction for example some
bacteria have an outer capsule that prevents the macrophage from
attaching, others are engulfed but are resistant to lysosomal
destruction and can even reproduce inside a macrophage(those are
especially a problem)
Slide 5
Continued About 1.5%of leukocytes are eosinophils which
specialize in defending against parasitic invaders Natural Killer
cells or NK cells do not attack the virus directly, it attacks the
virus infected body cells instead (cause the cell to lyse)
Slide 6
Inflammatory Response When a microorganism enters a damaged or
cut area it triggers an inflamatory response During this response
the precapillary arteries dilate and postcapillary venules
constrict which increases the ammount of blood In the area Causes
the redness and heat Histamine- a type of chemical signal that is
released by cells of the body in response to tissue injury
(increases dilation and permeability) Basophils produce histamine
and mast cells( found in connective tissue) Leukocytes and damaged
tissue cells also release prostagladins to promote blood flow to
the damaged area, this helps by delivering the elements that help
clot the wound This also helps the migration of phagocytic cells
from the blood into the injured tissues (chemokines also attract
phagocytic cells to the area) Another systematic response is a
fever which starts when it picks up certain toxins released from
the Certain leukocytes release pyrogens which increase the temp. of
the body (high fevers can be dangerous moderate ones help the body
fight by limiting growth of microorganism) Wide spread of
inflammation (septic shock) is the most common cause of death U.S.
critical care units
Slide 7
Antimicrobial Proteins Complement system- a type of system that
carries out a cascade of steps leading to the lysis of microbes
Some complement components help chemokines attract phagocytic cells
to the sites of infection Interferons- are nonspecific defense
proteins that are secreted by virus infected cells (dont help the
cell that has been infected instead they warn the nearby cells
which then develop chemicals that inhibit viral reproduction) That
effect limits the cell to cell spread of viruses in the body In
addition to its role as an antiviral agent it also activates
phagocytes, which enhances their ability to ingest and kill
microorganisms
Slide 8
Specific Immunity Lymphocytes(key cells in immune system)
generate efficient selective immune responses that eliminate
particular invaders in the body(B cells and T cells are the two
main lymphocytes) Bothe circulate in the blood, concentrated in:
spleen, lymph nodes and other lymphatic tissues Antigen- foreign
molecule that causes a specific lymphocyte to respond B and T cells
respond to different types of antigens, respond in different ways
that compliment one another Antibodies- are secreted by B cells to
counter specific antigens based on the shape of the molecule B
cells and T cells recognize specific antigens by using their
antigen receptors T cell receptors- are similar to membrane
antibodies, but they are never produced in a secreted form B and T
cells are created long before coming in contact with foreign
antigens, through this the body already has an enormous variety of
B and T cells with specific receptors
Slide 9
Antigens interact with specific lymphocytes Clonal Selection-A
lymphocyte is stimulated to divide and differentiate by the
microbes antigens Makes two clones, one that carries short lived
cells that combat the same antigen (effector cells) or long living
cells with receptors for the same antigen in case it needs to fight
it off later in life (memory cells) Primary Immunity Response-
selective proliferation and differentiation of lymphocytes that
occurs the first time the body is exposed to an antigen During the
10-17 day phase of the P.I.R. selected b cells and t cells make
antibody producing effector B cells known as plasma cells Secondary
immune response- occurs when the individual is exposed to the same
antigen at some later time, this response is much faster 2-7 days
and of greater magnitude and is more prolonged Secondary response
has a much larger amount of antibodies produced and they are more
effective
Slide 10
Distiguishing of Self from Nonself Lymphocytes that migrate
from the bone marrow to the thymus develop into T cells whereas
lymphocytes that continue to mature in the bone marrow become B
cells All lymphocytes are tested to see if there receptors match
other molecules in the body which would then lead to harming the
body, if such a lymphocyte is found they are either rendered non
functional or are destroyed by apoptosis (programed cell death) MHC
molecule carry a fragment of intercellular protein antigen in its
hemock groove, it then shows it to a antigen receptor so T cells
become aware of an infectious agent (two classes of MHC molecules)
Cytotoxic T cells-have antigen receptors that bind to protein
fragments (respond to presentation of fragments by killing the
infected cells) Helper T cells- have receptors that bind to
peptides displayed by the bodys II MHC molecules Wide distribution
of I MHC molecules is critical to our health Class II MHC are
mostly macrophages and B cells, these antigen presenting cells
collect remnants and present them to helper T cells which incite
other cells types to fight the pathogen
Slide 11
Immune Responses Humoral Immunity- involves B cell activation
and results from the production of antibodies that circulate in the
blood plasma and lymph, fluids that were long ago called humors
Cell mediated response- depends on the action of T-cells, immunity
gained through the transfer of humoral immunity (antibodies)
Circulating antibodies of the humoral response defend mainly
against bacteria, toxins, viruses that are present in body fluids T
cells of the cell mediated response are active against protozoa,
fungi, and parasitic worms Cell mediated response is crucial for
fighting off cancer cells classified as nonself
Slide 12
Closer look at Helper T-Cells and Cytotoxic T cells Found
mainly in cell types that engulf foreign antigens Interaction
between APCs and helper T cells is greatly enhanced by the presence
of CD4 (surface protein present on most helper T cells) Activated
helper T cells secrete several cytokines, proteins or peptides that
stimulate other lymphocytes Antigen activated cytotoxic T
lymphocytes kill cancer cells and cells infected by viruses or
other intercellular pathogens A cytotoxic T cell when activated by
I MHC and stimulated by IL-2 from a helper T cell becomes an active
killer, kills its target cell(APC) by releasing perforin a protein
that forms pores in the target cells membrane Ions and water then
flow into the target cell which swells and eventually lyses this
forces the pathogen into the open were it is destroyed by the
circulating antibodies The body defends against tumors in a similar
way, but when this fails the body uses Natural Killer cells that
can also lyse virus infected and or cancer cells
Slide 13
Humoral Response Once stimulated by both cytokines and antigens
the B cells proliferate and differentiate into a clone of antibody
secreting plasma cells and a clone of memory B cells Those antigens
are called T dependent antigens because they can stimulate antibody
production only with help from Th cells T independent cells-
polysaccharides and proteins with many identical polypeptides B
cells have class II MHC molecules B cells are much more specific to
which antigen it binds too as opposed to macrophages APCs are
general B cells specify Humoral response stimulates a variety of
different B cells, each giving rise to a clone of thousands of
plasma cells Each plasma cell estimated to secrete about 2000
antibody molecules per second over the its life span (4-5
days)
Slide 14
Antibody Structure and Function Neither membrane version of the
antibody nor the secreted body binds the entire molecule This
antibody interacts with a small accesible portion of the antigen
called the epitope (antigenic determinent) Single antigen such as a
bacterial surface has many epitopes, each able to produce a
specific antibody Most antibody have two identical antigen sites
for the epitope that caused the production Molecule consists of 4
polypeptide chains, Two identical heavy chains and two identical
light chains ( form a Y shaped molecule joined by disulfide
bridges) highly stable complex Polyclonal- prepared from many
different B cells: Monoclonal- composed from the same B cell Five
major classes of antibodies: IgM, IgG, IgA, IgD, IgE
Slide 15
Antibody Mediated Disposal of Antigen Neutralization- way in
which antibody binds and blocks the activity of an antigen EX:
antibodies neutralize virus by attaching to the molecules that the
virus needs to infect the host cell Opsonization- bound antibodies
enhance macrophage attachment to, and thus phagocytosis of, the
microbes Agglutination is also used to effectively neutralize
viruses by clumping Complement Fixation- one of the most important
antibody mediated disposal mechanism Activate during an infection
and are inactive in the absence of one, completion of the
complement cascade results in the lysis of many types of viruses
and pathogenic cells Can be activated in two ways the classical
pathway ( triggered by antibodies and bound by antigens and is
important to humoral response) and alternate pathway (triggered by
substances that are naturally present on many bacteria) does not
involve antibodies so it nonspecific
Slide 16
Rudimentary Immune system in Invertabrates Also have a very
effective immune system, which allows it to distinguish self from
nonself If two sponges are mixed the two cells will reaggerate
separating each others cells Mostly dispose of nonself through
phagocytosis, lately immunobioligists have discovered that some
have cytokines which enhance their ability to fight off infection
Depend mostly on nonspecific defenses helomin binds to microbes and
assists in the disposal (only in bugs) are likely ancient
precursors of antigens immunological memory found in earthworms but
not in sea stars
Slide 17
Immunity in Health and Disease Active immunity- immunity gained
from recovering from an infectious disease Immunization- also known
as vaccination which involves the individual receiving dead or
weakened cellls of the disease so they can develop immunity towards
it ( stimulates the immune response and immunological memory)
because of the antigens Passive Immunity- temporary immunity gained
by taking in anti-bodies or immune cells (lasts only a few weeks or
months) temporary because the system has been stimulated by
antigens Mothers can pass off passive immunity to their children
while they are pregnant provides protection for the baby until its
own immune system has matured This is used against fast acting
viruses like rabies, the injected antibodies will fight off the
virus for a few weeks until the persons own immune system kicks in
effectively the immune system also fights off other peoples cells
for example a skin transplant that does not match will look healthy
for 1or 2 days but then immune responses will attack and disfigure
it (the structure of the placenta prevents the mothers system from
harming the baby
Slide 18
Blood groups and Blood Transfusion Type A has A antigens, Type
B has B antigens, Type AB has both and type O has none Blood
transfusions are tricky because the persons blood type must match
or else the immune system will react to the antigens of the foreign
blood type Antibodies to foreign blood are already in the body even
if it has never been exposed to it before (they rise against
certain bacteria with similar epitopes) So if it Is type A it does
not have antibodies for A-Like bacterial epitopes since it
considers it as Self It can be harmful to the baby when a mother
who is rH negative lacks the rH factor but has a fetus which is rH
positive
Slide 19
Tissue Grafts and Organ Transplants Major Histocompatibility
Complex- encodes the protein fingerprint that is unique in every
individual causes the stimulation that rejects tissue grafts or
organ transplants Foreign MHC is antigenic which causes immune
system to respond against donated tissues or organs Use closest
compatible MHC available ( usually siblings if there is no
identical twin) in addition various medicines are required to
suppress the immune systems reactions (however during this
treatment a patient is much more susceptible to diseases Blood
transfusions follow the same route as for MHC as in the marrow is
matched as closely as possible (before this treatment the patient
is treated with irradiation to eliminate his or her own marrow
cells or abnormal cells)
