Immunity Flashcards
the immune system consists of
cells and tissues that defend the body against specific invading agents, such as bacteria, toxins, viruses, and foreign tissues
immune system is a functional system rather than
an organ system
specificity enables the immune system to
identify particular pathogens and to distinguish between self molecules and non-self molecules
immune system has a memory for encounters with previously identified antigens which allows
it to aggressively respond to subsequent invasions by these pathogens
cellular (cell-mediated) immunity uses
lymphocytes to directly attack and destroy foreign cells or host cells that are infected with bacteria or viruses or yeasts
cellular immunity protects against
parasitic worms, cancer cells, cells from transplanted organs
humoral (antibody mediated) immunity uses
antibodies to “label” pathogens for destruction by other mechanisms
humoral immunity protects agains
bacteria and bacterial toxins
naturally acquired active immunity occurs when
antibodies or T cells are produced in response to a particular pathogen
naturally acquired passive immunity is
temporary immunity resulting from the natural transfer of antibodies from an immunized donor to a non-immunized recipient (nursing mom)
artificially acquired active immunity results from
a vaccination
vaccine contains
either dead or attenuated pathogens that stimulate body to produce antibodies or T cells
artificially acquired passive immunity is
temporary immunity resulting from an injection of serum that contains antibodies that were produced outside of the body
horse serum can be used for the emergency treatment of
certain kinds of snakebite
an antigen is an
“antibody generating” molecule that shows immunogenicity and reactivity
immunogenicity is the
ability to provoke an immune response
reactivity is
the ability to interact with specific antibodies or cells
antigen may be a
microbe or a part of a micrbone, bacterial cell walls or bacterial toxins incompatible blood cells, or even pollen or egg whites can also by antigenic
most antigens are
large, complex proteins that are unique to each individual
an epitope, or an antigenic determinant,
is a specific region of an antigen that can trigger an immune response
most antigens have several
epitopes that either induce production of specific antibodies or activate specific T cells
haptens
are small molecules that attach to larger molecules and create unique complexes that the immune system can recognize as foreign (poison ivy, penicillin)
T lymphocytes are “born” in
red bone marrow from pluripotent stem cells
T lymphocytes travel to the thymus gland where thymic hormones stimulate them
to develop surface antigen receptors and become immunocompetent
when B cells or T cells become immunocompetent they
display unique surface receptors to recognize and bind a specific antigen
positive selection produces
identical T cells that are programmed to respond to a particular foreign antigen
negative selection eliminates
any T cells that bind to self-antigens
Fetal stems cells that remain in bone marrow
differentiate into B lymphocytes
the presence of a foreign antigen must
be detected for an immune response to occur
exogenous antigens are found
in the extracellular fluid outside of the body’s cells
-bacterial toxins, protein, dust
endogenous antigens are produced
inside of the body’s cells
-viral proteins, abnormal proteins associated with cancerous cells
each individual has a family of genes called the
major histocompatibility complex (MHC) on chromosome #6 that code from MHC proteins that act as “self-antigens”
MHC-I proteins are found
on the plasma membrane of all body cells, except erythrocytes
MHC-I proteins are continually
synthesized by a cell and transported to its plasma membrane
MHC-II proteins occur only
on antigen-presenting cells
human leukocyte antigens, HLA
MHC-II proteins help
T cells recognize foreign antigens
antigen presenting cells can be
B cells, macrophages, or dendritic cells that process and present exogenous antigens for destruction
a foreign antigen is
ingested by phagocytosis
digestive enzymes
split the antigen into fragments
antigen fragments are joined with
MHC protein molecules
antigen-MHC protein complex is inserted into
the plasma membrane of the APC to be “displayed”
APC migrates to
lymphatic tissue to prevent the “displayed” antigen to T cells
interleukins coordinate
the activities of various leukocytes that are involved in the immune response
lymphokines are produced by
lymphocytes
monokines are produced by
monocytes
cell-mediated immunity requires
the activation of a small number of T cells by a particular antigen
when an antigen presenting cell encounters and processes a foreign antigen,
it presents that antigen to a T cell, usually in a lymph node, which recognizes it and binds to the antigen fragments that are being displayed by the APC
activation also requires
co-stimulation by interleukins, prevents system from destroying healthy cells
once a T cell is activated,
it proliferates and differentiates into a clone of identical cells that can recognize the particular antigen and carry out the immune attack
proliferation peaks within
one week of exposure to the antigen
Helper cells recognize
an antigen MHC II complex and secrete interleukins
Helper cells attract
neutrophils, natural killer cells, and macrophages that stimulate phagocytosis
Helper cells activate
T cells and B cells
cytotoxic cells recognize
foreign antigens combined with MHC-I proteins and become kill cells that can deliver a “lethal hit” to target cell
** and turn off immune response once pathogen has been destroyed**
perforin forms
holes in the target cells membrane causing cell to burst
lymphotoxin activates
enzymes in the target cell that destroy DNA
tumor necrosis factor kills
cancer cells
regulatory cells
release interkeukins that will inhibit T cell and B cell activity
**and turn off immune response once pathogen has been destroyed*
regulatory cells also
prevent auto-immune reactions
memory T cells
remain from a proliferated clone
Memory T cells are programmed to
recognize the orginal antigen, so immune system can swiftly destroy that pathogen before symptoms of disease occur
antigen challenge
the first encounter between an immunocompetent and inactive lymphocyte and an invading antigen in the spleen or in a lymph node
antibody-mediated immunity
an indirect method of protection where B lymphocytes are activated to produce antibodies that bind to antigens in order to destroy them
binding of antigen
an antigen binds to one or more of the thousands of antigen receptors on the surface of an immunocompetent B cell, which links them together
- antigen is taken into B cell and broken into fragments
- epitopes are linked to MHC-II proteins and displayed on surface of B cell
when helper T cells recognize the antigen-MHC protein combination,
they produce interleukins and other cytokines that function as co-stimulators to activate the B cell
activated B cells
enlarge and divide and differentiate into a clone of plasma cells
plasma cells can
synthesize and release antibodies for a specific antigen at a rate of up to 2000 molecules per second for a period of four to five days
activated B cells that do not differentiate into plasma cells become
memory cells; respond rapidly and forcefully if antigen reappears in future
an immunoglobulin consists of
four large, complex polypeptide chains
each polypeptide chain contains
contains a variable region that is specific for a particular antigen and a constant region that will determine how the antibody works
constant region
determines class to which antibody belongs
variable region
forms antigen binding site
IgG antibodies are
the most abundant antibodies
IgG antibodies are found in
blood, lymph, and in the intestines
IgG antibodies protect against
bacteria and viruses by enhancing phagocytosis, by neutralizing toxins, by triggering complement system
IgG antibodies are the only antibodies that can
cross the placenta from mother to fetus
IgA antibodies are found
in body secretions, such as tears, saliva, mucus, and milk
IgA antibodies provide
localized protection against bacteria and viruses
IgM antibodies are
the first antibodies to be secreted by plasma cells after initial exposure to antigen
IgM antibodies include
anti-A and anti-B antibodies of the ABO blood group, which are potent agglutinating agents
IgM presence in blood plasma
usually indicates some kind of infection
IgE antibodies are found
mainly in tonsils, the skin, and in mucous membranes
IgE antibodies stimulate
mast cells and basophils during inflammation and allergy reactions
also release histamines
IgD antibodies are located
on B cell membranes where they act as antigen receptors
antibodies use _____ ways to disable antigens
many
antibodies neutralize an antigen by
binding to its active region and blocking its effects, since only certain regions of an antigen are pathogenic
IgG and IgM antibodies expose
complement-binding sits on the target cell which activates compliment system
antibodies have _______ antigen-binding sites so they can cause agglutination
multiple
antiboides link antigen molecules together to create
a complex that is too large to remain dissolved in the plasma
-precipitation makes antigens more susceptible to phagocytosis
antigens can or cannot destroy antigens by themselves
cannot
the immune system can recognize a particular antigen to which it has been exposed because of the
presence of long-lasting antibodies, memory T cells and memory B cells
antibody titer
can measure the level of a specific antibody present in the blood
a primary immune response
occurs following an initial exposure to an antigen and it produces and gradually releases antibodies over a period of time
a secondary immune response
occurs if the same antigen invades the body at a later time and gets recognized by the memory cells
a secondary immune response produces
a rapid, vigorous response within hours of re-exposure before antigen has chance to produce any symptoms of illness
