Immunology part 2 Flashcards
adaptive immunity depends on specific ____ receptors on ___ and ____
antigen receptors on T and B lymphocytes
each T or B cell expresses unique _____
antigen receptors on the surface
this adaptive system can react against any possible ____
antigen
adaptive immune system has tolerance to antigens present on ___
our normal cells
the adaptive immune system can develop ____
memory
define immunological memory
ability to accelerate and improve the response to repeated exposures to the same antigen
two types of adaptive immunity
humoral immunity and cell mediated immunity
humoral immunity involves what type of cells
B lymphocytes
B lymphocytes respond to antigens and do what?
trigger the production of antibodies that are specific to those same antigens
B-lymphocytes turn differentiate in ___ cells that then secret antibodies
plasma cells
in cell mediated immunity, what type of cells are involved?
cytotoxic T lymphocytes
cytotoxic T-lymphocytes are activated by ___, and then perform what function
specific antigens, they then kill the cells and microorganisms bearing the same antigens
what are helper T lymphocytes?
they regulate the function of B and cytotoxic T lymphocytes by recruiting and activating phagocytes, particularly macrophages
the two sides of adaptive immunity are not independent from ___ or ____
each other or innate immunity; there is interplay between all immunity systems at all times
3 key characteristics of adaptive immune response
- it is specific to the presenting antigens
- it takes time
- it has memory
B and T lymphocytes can respond to antigens that are
free or present on the surface of viruses, other microorganisms, foreign tissues, or transformed cells
each lymphocyte has receptors that are specific for just ___ ___ of antigen
one type
3 stages of adaptive immune response
- a foreign antigen is identified by a B or T lymphocyte
- antigen binds to specific receptor, lymphocyte is activated and under goes colonel expansion
- antibody and cytotoxic responses
in stage 2 of the the adaptive immune response, when the lymphocytes proliferate they will be responsible for
the 3rd stage, while some of the lymphocytes resulting from division will become memory cells
two signals needed for lymphocyte activation
- antigen recognition is signal one
2. cytokines produced by other immune cells provide the second signal
B cells transform to ___ cells and produce ____ against the antigen
plasma; antibodies
Cytotoxic t tells attack the ______
cells bearing the antigen
once the antigen has been eliminated, most of the responding lymphocytes will ____
die by apoptosis
after an antigen as been eliminated and the lymphocytes undergo apoptosis, the ____ cells persist and will respond ____ the next time the antigen appears
memory; faster
what are they primary lymphoid organs
bone marrow and thymus
bone marrow and the thymus are sites for ____
lymphocyte production and development
what type of lymphocyte is produced by primary lymphoid organs
naive lymphocytes that have not previously been exposed to a specific antigen
the bone marrow produces ___ ___ of lymphocytes
all types of lymphocytes
the thymus gland in the upper thorax above the heart completes the development of ____
T cells
most lymphocytes reside in ____
secondary lymphoid organs
secondary lymphoid organs are positioned to do what
survey what is coming into the body
a skin breach may invoke an immune response in the ___ ___ that drain the affected tissues
lymph nodes
if the insult it contaminated food, the immune response starts in ____ ____ under the mucosa of the small intestine
peyer’s patches
what secondary lymphoid organ responds to blood borne pathogens
the spleen filters them and starts the immune response
the ___ and ___ detect and respond to microbes that enter via the respiratory tract
tonsils and adenoids
activated lymphocytes proliferate through
colonel expansion, which means that all clones have the same antigen specificity
clonal expansion increases the number of __
cells that can act against the antigen that initiated the response
adaptive immune responses are self limited, meaning what?
they decline as the infection is eliminated by apoptosis, while some cells survive to provide immunological memory
the duration of each phase of the immune response depends on ____
the initial stimulus
the adaptive immune system improves with repeated _____
exposure to the same antigen
the initial exposure to an antigen is called what
the primary immune response and is mediated by naive lymphocytes
secondary immune responses are what
subsequent encounters with the same antigen that are faster, stronger, and better able to eliminate the antigen
secondary immune responses result from what
the activation of memory lymphocytes
b lymphocytes recognize ___ and ___ antigens
soluble and surface antigens
cytotoxic t lymphocytes recognize antigens presented by ___, ___, or ___ cells
infected, foreign, or transformed cells
After activation and expansion, ____ cells destroy the antigen-bearing cells directly
cytotoxic t cells
helper T-lymphocytes recognize antigens displayed by ___ cells
antigen presenting cells
helper t lymphocytes secrete ____ which stimulates
secrete cytokines to stimulate B and T lymphocytes
what are regulatory T cells
they limit the activation of other lymphocytes, specifically T cells, to prevent autoimmunity
natural killer cells recognize ___ or ___ cells, like cytotoxic t cells, but their responses are not ___
infected or transformed cells but their responses are not specific
natural killer cells are considered to be a part of the ___ immunity system
innate
the innate immune system recognizes generic markers called ___ and ____, while the adaptive immune system recognizes each ___ specifically
PAMPs and DAMPs; antigen
each lymphocyte clone has receptors specific to how many antigens
1 antigen
there are billions to hundreds of billions of clone lymphocytes, which means that they can response to ___
that corresponding number of antigens
the antigen receptors in b-lymphocytes are ____ which are bound to the ___
immunoglobins which are bound to the membrane
the immunoglobin receptors on the b lymphocytes are the same immunoglobins that will be
secreted as antibodies by the plasma cells
these immunoglobins of the b cells recognize what
proteins, lipids, carbohydrates, nucleic acids, and simple chemical groups
T cell receptors are also ____ proteins that recognize ___ displayed on ____ cells
membrane proteins that recognize peptides displayed on antigen presenting cells
the antigen receptors are associated with ___ that act to to do what?
other proteins that initiate intracellular signals when an antigen is recognized
the intracellular signals produced when an antigen is recognized can cause lymphocytes to do what
divide, differentiate, or under some conditions, die
the adaptive immune system discriminates between __ and __
self and non self
the recognition of self and non self antigens is based on the display of
peptides bound to proteins of the major histocompatibility complex (MHC)
all nucleated cells express what type of MHC
MHC 1
MHC 1 complexes display peptides of abnormal or normal cell proteins on the surface?
normal cell proteins
if the protein displayed on the MHC 1 complex is abnormal, this allows the adaptive immune system to do what?
determine if the cell’s protein production machinery has been taken over by an intracellular infection or cancer
if peptides presented on the surface are normal, the cell is ____ by the immune system; if the fragments are abnormal, that initiates a ___ ___ response that kills the abnormal cell
ignored; cell-mediated response
class 2 MHC proteins are expressed only by
antigen presenting cells such as macrophages, dendritic cells and B cells
what do antigen presenting cells do
they capture and process foreign matter and then display their peptides coupled to class 2 MHC to helper t cells
the recognition of a displayed peptide by a helper T cell as non self does what?
triggers an immune response, initiating both cell mediated and antibody mediated responses
what are MHC polymorphisms
differences in class 1 and 2 MHC from person to person that results in variation in how the antigens are processed and presented to the immune system
how do MHC polymorphisms explain why a recipient might reject a donor organ?
because the recipient and donor do not match perfectly due to the type 1 MHC from the transplanted organ cells presenting the incorrect “self” antigens to the recipient’s immune system
there is individual variation in microbial antigenic peptides presented by MHC, what does this mean?
that the MHC receptors of 2 different individuals may display different peptides derived from the same virus, generally does not have a large effect in immune response
microbial antigens processed by antigen presenting cells enter the class ___ MHC pathway
class 2
Process of the MHC 2 pathway
- MHC-antigen complexes are displayed on surface of APC
- complex is recognized by helper T cell
- activation and expansion
- helper T cells stimulate macrophages and enhance activation, expansion and differentiation of B cells into plasma cells that produce and secrete the antigen specific antibody
antigens form intracellular microbes or from tumor cells are processed as part of the recycling of cellular components, these peptides are then coupled to what
class 1 MHC and displayed on the surface for recognition by cytotoxic t lymphocytes
in order for the cytotoxic t lymphocytes to be fully activated after identifying an antigen, what needs to happen
helper t cells must be activated via the class 2 MHC pathway
naive T lymphocytes have to be presented the antigens to start what processes
clonal expansion and differentiation into effector and memory cells
differentiated effector T cells need to see the ____ again in order to re-activate their functions
antigens
what are the most effective antigen-presenting cells for naive helper T lymphocytes
dendritic cells
what antigen presenting cell is abundant in all tissues?
macrophages
in cell-mediated immune responses, the ___ cells and ___ display the antigens to helper t cells
dendritic cells and macrophages
when helper t cells are activated they enhance ____ and enhance _____
phagocytosis and the humoral immune response
b lymphocytes display antigens to ____ cells to enhance the humoral immune response
helper t cells
dendritic cells that capture antigens at epithelial barriers migrate to where
lymph nodes
in transit to the lymph nodes, the dendritic cells change from _____ to
____ cells
antigen capture to antigen presenting cells
macrophages do not migrate, they instead remain in the ___ and present antigens to the ____ cells recruited to the site
tissue; T cells
activated antigen-presenting cells express non-specific costimulating signals which is a ____ process
2 signal process
if helper T cells do not work, what does this mean
humoral and cell-mediated responses are severely impaired; this is what happens in patients with HIV
soluble antigens are picked up by ___ cells residing in the lymph nodes
dendritic cells
blood-borne antigens are handled by ___ cells in the ____
dendritic cells in the spleen
humoral immune response begins with the ____ receptor
B-cell receptor
what is the B-cell receptor composed of
4 peptide subunits, two identical heavy chains and two identical light chains
the diversity in antigen specificity (the antigen binding site) is created by what
the assembly of the gene segments on the receptor
each arm of the B receptor has an antigen binding site that is ____ for the B cell where the receptor resides
unique/specific
when the specific antigen binds to the b cell receptors, other members of the receptor complex ____ and ___, initiate intracellular signaling pathway
IG-alpha and IG-beta
IG-alpha and IG-beta initiating the intracellular signaling pathway of the B cell does what
activates the B cell
the arrangement of the receptor interacting with the receptor complex of the B cell separates what
antigen recognition taking place at the arms of the receptor and is specific, from the signal transduction, mediated by units that are not specific
the stem of the immunoglobin on the b cell is known as the ___ region, or ___
constan region or Fc
the constant region is important for what
interaction of immunoglobins with other components of the immune systems
the constant region determines the ____
immunoglobin class
how many immunoglobin classes are there?
5: A, D, E, G, M- each one serving a function
process for humoral immunity (steps)
- naive B lymphocytes use IgM and IgD antigen receptors
- b lymphocytes are activated by the antigens that are specific for their receptors
- full b lymphocyte activation leas to proliferation of antigen specific cells (clonal expansion)
- differentiation of b cells into plasma cells
- plasma cells secrete antibodies that have the same specificity as the receptors on the naive b cells
during the differentiation process of humoral immunity, some b lymphocytes switch to a different Ig class that has a ____ affinity for the antigen
greater
when b lymphocytes switch to a different Ig class with a greater affinity for the antigen, this is called what
class switching and affinity maturation, producing antibodies with improved antigen specificity
during the differentiation stage of humoral immunity, some b cells differentiate into ___ cells
memory
antibodies do or do not kill microbes
they DO NOT kill microbes directly
how do antibodies destroy microbes if they do not kill them
they mark them for destruction by phagocytosis, by complement, and by natural killer cells
bound antibodies act as ___
opsonins
phagocytes have receptors for the ___ portion of immunoglobins
Fc
when antibodies bind to antigens on a microbe, phagocytes bind ___ region and that triggers ____
Fc regions and that triggers phagocytosis
antibodies initiate the classical ___ pathway
complement
the classical complement pathway includes ___ and the ___ ___ complex
C3b (another opsonin) and the membrane attack complex
antibodies neutralize microbes and toxins by doing what
blocking surface antigens needed for their function
natural killer cells have one special response to antibodies, which is?
they react to the c3b bound to bacteria by releasing cytotoxic chemicals
natural killer cells reacting to the C3b bound to bacteria is a process called what
antibody-dependent cellular cytotoxicity, which is an example of an innate immune response that is made specific by the antibodies
when is IgM made and what does it do
made when naive b cells are first activated and is good at activating complement
IgG is most abundant where
in the blood
IgG is a good ____, ____, and ____
opsonin, complement activator, and initiator of antibody-dependent cellular cytotoxicity
IgG crosses the ___, which gives the fetus a head start on immunity
placenta
which Ig class is the most abundant
IgA because it is present in mucosal surfaces and secretions
IgA provides humoral immunity where
in the digestive, respiratory, and reproductive tracts
IgE antibodies are important for the immune defense against what
large parasites
aside from fighting large parasites, IgE is also involved in
allergic reactions
T-cell receptors are two chain membrane proteins with ____ regions
antigen specific regions
T cell receptors have two heterodimeric forms, ___ and ___
alpha-beta or gamma-delta
what creates the diversity needed to respond to all possible antigens in the T cell receptors
the genes for alpha, beta, gamma, and delta are assembled by mixing gene segments
the T cell receptors are linked to ___ that do what
other integral membrane proteins that iniate a signaling cascade when the antigen binds to the receptor
The t cell receptor does not combine with the antigen directly, it instead does what
interact with antigen present by an MHC protein, either type 1 or 2, and then the T cell receptor interacts with the whole complex (including coreceptors such as Cd4 or Cd8)
CD4 is a coreceptor for what type of t cells
helper t cells
CD8 is a coreceptor for what type of t cell
cytotoxic t cells
what is the job of the co receptors of the t cell
to strengthen the interaction of the t cell with the MHC complex
helper t cells are activated in 3 steps:
- antigen presentation
- a co-stimulus given by membrane proteins
- the secretion of stimulating cytokines by the antigen presenting cell
helper t cells recognize antigens bound to class __ MHC of antigen presenting cells
class 2 MHC
the helper t cell specific for the antigen bound to an MHC 2 complex is assisted by the ___ marker on the surface of the T cell, which acts to stabilize ___
CD4; the interaction with the MHC-antigen complex
the helper t cell must also match with other ____ on the antigen presenting cell, and it must receive ___ to be fully activated
surface proteins; cytokines
B-lymphocytes are ____ ____ cells, with one key difference: ____
antigen presenting cells; the antigen binds to the immunoglobin on the surface of the B cell, then the antigen is internalized, processed and attached to the class 2 MHC and displayed
the antigen-presenting function of the B-cell is different form the differentiation step into ___ cells, and serves to _____
plasma cells; amplify the response to the antigen
once the antigen is displayed on a B-cell, the ____ can interact with it
helper T cell
once activated, the helper T cells secrete ____ that coordinate and enhance the adaptive and innate immune responses
cytokines
activation of helper t cells is necessary for the normal response of ___ cells and ____
B cells and cytotoxic T lymphocytes
the process of antigen presentation to cytotoxic t cells serves to identify ____
intracellular antigens
antigens come from where
intracellular microorganisms or cancer proteins
antigens are processed and presented by the class ____ MHC on the membrane, where they are matched by the specific receptor on the corresponding cytotoxic T cell
class 1 MHC
viral infections and cancer transformation make the affected cells produce and display ___
inappropriate antigens
____ cells identify the foreign antigens on the surface of cells and at the same time, ___ cells are activated by macrophages that process the foreign antigens independently
cytotoxic t cells; helper t cells
activated helper t cells release ____ and other cytokines
interleukin 2
what is interleukin 2
an autocrine signal for helper t cell proliferation and a paracrine signal for cytotoxic t cell activation
activated cytotoxic t cells by helper t cells bind to ___
target cells
once in close contact with the target cell, cytotoxic t cells release
perforin, a protein that creates a pore on the target’s membrane
cytotoxic t cells also release ___, which does what
granzyme, which is a collection of cytotoxic enzymes that trigger cell death
immunological memory allows the adaptive immune system to respond ____ to repeated exposures to the same infection
faster and better
during an infection, the humoral response to a first encounter takes time, but exposure to the same antigen activates
memory B cells and that gives a faster and stronger immune response, mostly with IgG antibodies with higher affinity for the antigens
T cell memory follows the same dynamics as B-cell, which is?
the first exposure to an antigen results in the creation of a pool of memory cells for cytotoxic and helper t cells
how does a vaccine take advantage of immunological memory
by serving as the initial exposure to an antigen so that subsequent exposures trigger a faster and stronger immune response, preventing the onset of disease
the assignment of antigen specificity to T lymphocytes depends on the random arrangement of gene segments during their production and because of the randomness, what can happen
self-reactive lymphocytes are always produced during development and must be eliminated
where does the process of eliminating self reacting t lymphocytes take place?
thymus
what happens in the thymus to eliminate these self reactive t lymphocytes
the cytotoxic and helper t cells are presented with self-antigens and if they interact too strongly or too weakly, they are eliminated
the process of eliminating self reactive t lymphocytes is called what
central tolerance because it is established in the organ where the t lymphocytes complete their development
central tolerance to self antigens during fetal and early post-natal life depends on what two processes
- clonal deletion; the elimination by apoptosis of T cells whose receptors bind to self proteins
- development of regulatory t cells that recognize self antigens and once in circulation, block the activation of harmful self-reacting lymphocytes
failure of self-tolerance leads to what
auto-immune diseases
if we learn how to induce self-tolerance, we can do what?
prevent or control unwanted immune reactions, examples: allergies and autoimmune diseases, rejection of organ transplants
HIV targets the cell type ____
helper t cells by using CD4 to gain access into the cells; patients can no longer coordinate immune systems
HIV can remain ___ for a long time
latent
eventually, the HIV virus replicates ___ and manages to ____ the immune system
quickly and manages to avoid the immune system
as HIV replicated, ___ cells are lost and once that cell count becomes low enough, the patient becomes susceptible to opportunistic infections and cancers and HIV becomes ___
helper t cells; AIDS
patients with IBD, Chron’s disease, and ulcerative colitis have an _____
uncontrolled chronic inflammation
patients with IBD, Chron’s or ulcerative colitis have a predisposition to ____ inflammatory responses to the microbiome of the gut
exaggerated
