ch 11.3- immune system Flashcards
diseases caused by viral pathogens
include HIV, AIDS, influenza, measles, and herpes.
leukocytes
white blood cells
lymphocytes
White blood cells found mainly in the
lymphatic organs (T cells, B cells, natural killer cells)
that originate from the bone marrow. T cells mature
in the thymus while B cells mature in the bone
marrow.
parts of the innate immune system
external immunity: Physical/physiological
barriers preventing pathogen entry. These barriers
include skin, mucous membranes, chemical
secretions, cilia, and symbiotic bacteria.
Internal immunity: Internal defenses activated
by the innate immune system to neutralize
pathogens that have entered. The body’s internal
immunity is composed of the inflammatory
response, complement proteins, and phagocytic
and natural killer cells.
mast cells
type of leukocyte responsible for the
first part of the inflammatory response, known as
rally signaling:
mast cell function steps
- Mast cells sit in the tissue in preparation for
injury. - If there is an injury, mast cells will release
histamine, which dilates blood vessels. This
increases blood flow and makes vessels more
permeable to let immune cells into the tissues. - Mast cells also release heparin, an anticoagulant
that prevents blood clotting.
inflammatory response
● Swelling: Permeable capillaries result in fluids
leaking into tissues.
● Loss of function: Body part with inflammation
becomes less usable.
● Increased heat: Increased blood flow results in
higher temperature.
● Pain: Throbbing caused by swelling, which puts
continuous pressure on nerve endings.
● Redness: Increased blood flow causes redness of
skin.
A fever can also occur due to the inflammatory
response; this is controlled by the brain and causes a
systemic response to kill pathogens with higher
temperatures.
diapedesis
is the process by which cells move from
the capillaries to the tissues in order to fight
pathogens.
granulocytes
are cells in the innate immune system
with specific granules in their cytoplasm. The four
types of granulocytes include neutrophils, eosinophils,
basophils, and mast cells.
Mnemonic:
Five main types of leukocytes from highest to lowest
in quantity → Never Let Monkeys Eat Bananas
neutrophils
Phagocytes in innate immunity that
make up over half of all leukocytes. Neutrophils
are the most common type of leukocyte found in
blood and are one of the first cells to be recruited
to a site of inflammation.
lymphocytes
B cells, T cells, and natural killer
cells. B and T cells are part of adaptive immunity
and must be activated. Natural killer (NK) cells
are part of innate immunity and attack
virally-infected cells + cancerous cells. NK cells
use perforin (create holes) and granzyme
(stimulate apoptosis) to lyse cells. B and T cells
are the most common type of leukocyte found in
lymph.
monocytes and macrophages
Phagocytes in innate
immunity. Monocytes are immature form found in
blood vessels and macrophages are mature form
after diapedesis. Can also act as antigen-presenting cells to activate adaptive
immunity.
eosinophils
Part of innate immunity and have
granules that can be released to kill pathogens,
especially parasites.
basophils
Least numerous leukocyte; contain
granules with histamine (vasodilation) and
heparin (an anticoagulant to prevent blood
clotting). Very similar to mast cells, except
basophils circulate as mature cells while mast
cells circulate as immature cells.
histamine function
vasodialation
herapin
anticoagulant to prevent blood clotting
dendritic cells
part of innate immunity and
scan tissues using pinocytosis (cell drinking) and
phagocytosis (cell eating). They act as
antigen-presenting cells like macrophages,
migrating to the lymph nodes to activate adaptive
immunity.
Toll like receptors
Macrophages and dendritic cells use toll-like
receptors (TLR’s) to recognize conserved parts of
microbes. Binding to these receptors triggers
phagocytosis and activates the innate immune
system.
interferons
secreted by virally-infected cells and
bind to non-infected cells to prepare them for a virus
attack. Also, interferons help activate dendritic cells.
platelets
are also a type of immune cell involved in
activating the innate immune system. These anucleate
cells regulate macrophages and dendritic cells.
complement system
is a group of
approximately 30 proteins that aid immune cells in
fighting pathogens. While small, these proteins turn
each other on through the activation of a
complement cascade, producing a large effect.
Upon recognizing a pathogen, a chain reaction of
protease activity is triggered for the proteins to
activate each other.
complement protein actions
● Tags antigens for phagocytosis in a process called
opsonization.
● Amplifies inflammatory response (e.g., binds to
mast cells for increased histamine release).
● Forms a membrane attack complex (MAC),
which pokes holes in pathogens and lyses them.
antigen and epitope
An antigen is an immunogenic foreign molecule and
is the target of the immune response. The epitope is
the important part of the antigen that is recognized
by the immune cell.
major histocompatability complex
The immune system recognizes foreign cells and
antigens using major histocompatibility complex
(MHC) molecules. Once recognized, the immune
system destroys the foreign or infected cell.
MHC class I
MHC class I is a surface molecule on all nucleated
cells that present intracellular antigens. Each
genetically different individual will have a unique MHC
I molecule, thus the immune system can use this to
distinguish between self and non-self cells.
MHC class II
is a surface molecule on
antigen-presenting cells (dendritic cells, macrophages)
that present extracellular antigens.
organ transplants
that have different MHC I may
lead to failure and rejection, so immunosuppressants
are given to transplant patients. Autoimmune
diseases occur when the immune system attacks self
MHC I.
Identical twins have identical major histocompatibility
complex molecules. This allows identical twins to
donate organs to each other without the need for
immunosuppression (the donated organ cells won’t be
marked as foreign).
B cells
control antibody-mediated immunity
(humoral immunity) by managing the production
and release of antibodies. They can also act as
antigen-presenting cells.
BCRs
B cell receptors (BCRs) are located on B cells and
bind to antigen epitopes either free-floating or on
APCs. Each B cell has a unique BCR.
clonal selection model
describes the
development of one type of BCR for every B cell.
Through clonal expansion, these B cells divide into
either plasma cells (antibody-secreting cells) or
memory B cells (to be activated later in case of
another attack).
memory b cells
survive for a long time and lay
dormant until reactivated by the same antigen that
triggered the original clonal expansion. They are
the key to vaccinations because vaccines cause
memory B cell production for later reactivation. After
reactivation, memory B cells cause massive antibody
production.
antibodies
are structurally .
identical to BCRs but freely circulate in blood and
lymph. They can tag antigens for phagocytosis,
neutralize the antigen by coating it, or activate the
complement system. Antibodies contain light
chains and heavy chains that are linked together by
disulfide bonds. In addition, the variable region
recognizes different antigens while the constant
region is the same for antibodies within the same
class.
igM
Present in a pentameric form and is the
largest antibody. The first antibody to be
produced; activates the complement system.
igA
Present in a dimeric form and found most
abundantly in bodily secretions. Newborns
receive passive immunity through breast milk
containing IgA.
igE
Monomer that is present on basophils and
mast cells as antigen receptors. When bound to
an allergen, it triggers histamine release and an
allergic reaction. Think Ig sneEze.
igD
Monomer that we have very little information
about. Only small amounts are produced.
igG
Monomer that is the most abundant
antibody in circulation. Also the only antibody
that can cross the placenta to give fetus passive
immunity. Helps the complement system to
cause opsonization (tags antigens and
subsequent phagocytosis). Helps IgM activate
the complement system.
T cells
control cell-mediated immunity by directly
acting on cells instead of sending antibodies out.
T cells must bind to antigens presented on APCs
(antigen-presenting cells) to be activated. There
are two ways antigens may be presented to T cells:
- MHC I presentation
- MHC II presentation
TCRs
unique just like BCRs,
binding only to one type of antigen per T cell. Thus, T
cells also undergo clonal selection just like B cells.
MHC I presentation
T cells differentiate into
cytotoxic T cells (CD8+), which directly kill
infected cells through perforin (poke holes) and
granzymes (cause apoptosis). However, T cells are
different from natural killer cells because they
are more specific and require antigen
presentation.
MHC II presentation
T cells differentiate into
helper T cells (CD4+), which release interleukins
to boost both innate immunity and adaptive
immunity. These interleukins help attract innate
immune cells and increase proliferation of other T
and B cells.
passive immunity
refers to the immunity one
organism gains from receiving the antibodies from
another organism that already has that immunity.
For example, a fetus gains passive immunity through
the placenta (IgG) while a newborn gains passive
immunity through breast milk (IgA).
immuno naive
The fetus and
newborn are referred to as immuno-naive because
they do not yet have their own active immunity.
ative immunity
refers to the immunity an organism
gains from being infected once already by a pathogen.
artificial immunity
Type of active immunity
A vaccination introduces the antigen or pathogen in a
deactivated state to stimulate active immunity, which
is referred to as artificial immunity in this case and
induces memory B and T cell formation.
