Exam 1: Immunity Flashcards
Barrier defenses of mammals in innate immunity include
mucous membranes and the skin
play both a physical role (literal barrier) and chemical, secretions include lysozymes that destroy bacteria cell walls
The two main types of phagocytic cells in mammalian innate immunity are
neutrophils and macrophages
TLR proteins trigger
internal innate immune defenses, including production of cytokines and antimicrobial peptides
Neutrophils are located ___, part of the ___ immune system, and are attracted by __
circulate in the blood
innate
signals from infected tissues and then engulf/destroy pathogen
Macrophages are ___ , part of the ___ immune system, and are located ___
larger phagocytic cells
innate
located throughout the body
Dendritic cells are part of the ____ immune system and are
mainly populate tissues, such as skin, that contact the environment. They stimulate adaptive
immunity against pathogens that they engulf.
Eosinophils are part of the ___ immune system and are
innate
important in defending against multicellular invaders, such
as parasitic worms. Upon encountering such parasites,
eosinophils discharge destructive enzymes.
Natural killer cells are part of the ___ immune system and
innate
circulate through the body and
detect the abnormal surface proteins found on some
virus-infected and cancerous
cells. Natural killer cells do not
engulf stricken cells. Instead,
they release chemicals that lead
to cell death, inhibiting spread
of the virus or cancer.
Mast cells are part of the ___ immune system and are
innate
are found in connective tissue and make key
contributions to the inflammatory response, described next, as well as to allergies,discussed later.
The local inflammatory response, part of the ___ immune system, is a set of events triggered by signaling molecules
released upon injury or infection.
innate
The local inflammatory response begins when
activated macrophages discharge cytokines, signaling molecules that recruit neutrophils to the site of injury or infection. In addition,
mast cells release histamine at sites
of damage.
When histamine is released by mast cells during the local inflammatory response, it
triggers nearby blood vessels to dilate and become more permeable, resulting in redness and increased skin temperature
Describe the middle of the local inflammatory response.
Activated complement proteins..
Enhanced blood flow to the site….
resulting in…
cycles of signaling and response continue inflammation.
Activated complement proteins promote further histamine release, attracting more phagocytic cells to
the site of injury and infection
enhanced blood flow to the site helps deliver antimicrobial peptides
accumulation of pus
At the end of the local inflammatory response, pus and excess fluid
are taken up as lymph, the fluid transported in the network of vessels known as the lymphatic system
lymph nodes contain macrophages, whose purpose is to
engulf pathogens that enter the lymph from interstitial fluid
dendritic cells typically reside outside the lymphatic system, when they migrate to the lymph nodes
migrate to lymph nodes after interacting with a pathogen they interact with other immune cells to stimulate adaptive immunity.
Interferons, part of the ___ immune system, are proteins that
innate
Virus-infected body cells
secrete interferon proteins that induce nearby uninfected
cells to produce substances that inhibit viral replication.
The complement system, part of the ___ immune system, consists of roughly 30 proteins in the ___ that are activated by
innate and adaptive
blood plasma
substances of the surface of many pathogens
How do the molecules that activate
the vertebrate TLR signal transduction pathway differ from the
ligands in most other signaling pathways
Whereas the ligand for the TLR receptor is a foreign molecule,
the ligand for many signal transduction pathways is a molecule produced by the
organism itself.
The adaptive immune response develops faster/slower than innate
slower
The adaptive response is ____ by previous exposure to a pathogen, unlike innate
enhanced
Lymphocytes, part of the ____ immune system, are types of white blood cells known as ___
adaptive
T and B cells
T cells mature in the ____
thymus
B cells mature in the ____
bone marrow
An antigen is
any substance that elicits a B or T cell response after binding to a lymphocyte antigen receptor
A given lymphocyte will contain ___ type of antigen receptor
one
Infection by a pathogen will trigger the activation of lymphocytes, causing the antigen receptor to
become more specific
An epitope is
an accessible portion of an antigen that binds to a lymphocyte’s antigen receptor
Describe the basic structure of a B cell receptor
Y shaped protein with four polypeptide chains
two identical heavy and two identical light chains
Linked together by disulfide bridges
The constant or C region in a B cell antigen receptor is where ___. In contrast, the variable or V region is where ____amino acid sequence varies extensively from one B
cell to another.
amino acid sequences vary little among the receptors
on different B cells.
Together, parts of a heavy-chain V region and a light-chain V region form an _____ binding site for an antigen. Each B cell antigen receptor has two ___ antigen-binding sites
asymmetric
identical
Antibodies are secreted by B cells during the
Binding of a B cell antigen receptor to an antigen (an early step in B cell activation), leading to
formation of cells that secrete a soluble form of the receptor (the antibodies/immunoglobin)
Antibodies differ from B cell antigen receptors because
they lack a membrane anchor, and can bind to antigens on the surface of pathogens OR free in body fluids
Describe the general structure of T cell antigen receptors
twin towers consisting of an alpha chain and a beta chain, linked by a disulfide bridge
at the base is a transmembrane region that anchors it to the cell’s membrane
The variable and constant regions of the T cell receptors form a
single antigen binding site
Whereas the antigen receptors of B cells bind to epitopes
of intact antigens protruding from pathogens or circulating free in body fluids, antigen receptors of T cells bind only
to fragments of antigens that are displayed, or presented,
on the surface of host cells.
The MHC molecule can best be defined as
The host protein that displays
the antigen fragment on the cell surface for a T cell receptor to bind to
MHC molecules are essential for antigen recognition by T cells because
they display antigen fragments
Antigen recognition can best be defined as
an antigen fragment inside the host cell binds to an MHC and is brought to the cells surface so the T cell can get it
List the four major characteristics of adaptive immunity
First, the immense repertoire of lymphocytes and receptors
enables detection of antigens and pathogens never before
encountered.
Second, adaptive immunity normally has self-tolerance
Third, cell proliferation triggered by activation greatly increases the number of B and T cells specific for an antigen.
Fourth, immunological memory
What is the purpose of recombinase in B cell development?
links one light-chain V gene segment to one J segment, forming a single exon
In any given cell, ____ (number) allele of a light-chain segment and ____ (number) allele of a heavy gene are rearranged
one
TorF rearrangements in a B cell development are constantly changed according to pathogens in the body
False, only one rearrangement is possible
Antigen receptors can be synthesized in a B cell after
the light and heavy chain gene have been rearranged, the genes are transcribed, and the transcripts are translated
In adaptive immunity, how does the body distinguish self
from nonself?
as lymphocytes mature in the bone marrow or
thymus, their antigen receptors are tested for self-reactivity
How does an effective adaptive response develop?
An antigen is presented to a steady stream of lymphocytes in
the lymph nodes until a match is made
Once activated, a lymphocyte undergoes cell division.
What are effector cells?
Cells developed after lymphocyte activation and clonal selection. They are short-lived that take effect immediately against the antigen
Compare B cell effector cells to T cell effector forms
B cell: plasma cells which secrete antibodies
T cell: helper T cells and cytotoxic T cells
Memory cells are
remaining cells in lymphocyte clonal selection which are long-lived that can give rise to effector cells if antigen is encountered again
Primary immune response, an aspect of immunological memory, consists of
The effector cells formed
by clones of lymphocytes after an initial exposure to an anti-
gen produce a primary immune response
The secondary immune response, an aspect of immunological memory, is
a response that is faster
(typically peaking only 2–7 days after exposure), of greater
magnitude, and more prolonged in comparison to primary
The secondary immune response relies on ___ cells generated upon
memory
initial exposure to an antigen
Explain how memory cells strengthen the immune response
when a pathogen is encountered for a second time.
Generating memory cells ensures both that a receptor specific
for a particular epitope will be present and that there will be more lymphocytes
with this specificity than in a host that had never encountered the antigen.
Compare the humoral immune response and cell-mediated immune response, both of which are part of ___ immunity
adaptive
The humoral immune response pro-
tects the blood and lymph through antibodies which help neutralize or eliminate toxins and pathogens in body fluids.
In the cell-mediated
immune response, specialized T cells destroy infected host
cells.
True or false: The humoral immune response is the only response which can include a primary and secondary response (enabled by memory cells)
False, both humoral and immunity can include primary and secondary
The helper T cell activates the ___ response(s).
humoral and cell-mediated immune responses
Before a helper T cell can activate the humoral or cell-mediated immune responses two conditions must be met. What are they?
A foreign molecule must be present that can bind to helper T cell antigen receptor
This antigen must be displated on the surface of an antigen-presenting cell such as a dendritic, macrophage, or B cell.
Like immune cells, infected cells can display foreign
antigens on their surface. What then distinguishes antigen-
presenting cells from infected cells?
Most body cells
have only the class I MHC molecules, but antigen-presenting
cells have both class I and class II MHC molecules. The class
II molecules provide a molecular signature by which an
antigen-presenting cell is recognized
Describe the interaction between the helper T cell and antigen-presenting cell
The antigen receptors on the surface of the helper T cell bind
to the antigen fragment and to the class II MHC molecule
At the same time, an accessory protein called CD4 on the helper T cell surface binds to the class II MHC molecule, helping keep the cells joined.
As the two cells
interact, signals are exchanged in the form of cytokines
Antigen presentation by a
dendritic cell or macrophage activates a helper T cell, which
then proliferates, forming a clone of activated cells. In
contrast, B cells
B cells present antigens to already activated helper
T cells, which in turn activate the B cells.
B cells proliferate due to the stimulation from
both an antigen and cytokines
How does the pathway for antigen processing and display in B cells differ from other antigen-presenting cells?
A macrophage or dendritic cell can present fragments from a wide variety of protein antigens, whereas a B cell presents only the
antigen to which it specifically binds
When an antigen first
binds to receptors on the surface of a B cell, the cell takes in
a few foreign molecules by receptor-mediated endocytosis. The class II MHC protein of the B cell then
presents an antigen fragment to a helper T cell. This direct
cell-to-cell contact is usually critical to B cell activation.
Neutralization in antibodies is the process in which
antibodies bind to proteins on the surface of a virus. The bound antibodies prevent viral infection
of a host cell, thus neutralizing the virus.
TorF: antibodies can only perform neutralization on viruses
False, they can neutralize toxins as well
Describe the process of opsonization
Antibodies that are bound to antigens on
bacteria do not block infection, but instead present a readily
recognized structure for macrophages or neutrophils, thereby
promoting phagocytosis
How do antibodies sometimes work together with the proteins of the complement system?
Form a membrane attack complex
Binding of a complement protein to an antigen-antibody
complex on a foreign cell triggers events leading to formation
of a pore in the membrane of the cell. Ions and water rush
into the cell, causing it to swell and lyse
How can antibodies bring about the death of infected body cells?
If antibodies specific for epitopes on these viral proteins
bind to the exposed proteins, the presence of bound anti-
body at the cell surface can recruit a natural killer cell.
Cytotoxic T cells, which are part of the _____ immune response, use
cell-mediated
toxic proteins to kill cells infected by pathogens before the pathogens mature
To become active, cytotoxic T cells require
signals from helper T cells and interaction with an antigen-presenting cell
CD8 is the
accessory protein that connects a class 1 MHC molecule and cytotoxic T cell
Immunization can best be defined as
the use of antigens artificially introduced into the body to generate an adaptive immune response and memory cell formation
Compare active to passive immunity
active: the defenses that arise when a pathogen infection or immunization prompts an immune response
Passive: A different type of immunity results when, for example, the
IgG antibodies in the blood of a pregnant female cross the placenta to her fetus. (antibodies must be developed by another individual)
Why are MHC cells the primary cause of immune rejection?
Each of us expresses
MHC proteins from more than a dozen different MHC genes.
Furthermore, there are more than 100 different versions, or
alleles, of human MHC genes. As a consequence, the sets of
MHC proteins on cell surfaces are likely to differ between any
two people, except identical twins. Such differences can stim-
ulate an immune response in the recipient of a transplant or
graft, causing rejection.
If a child were born without a thymus gland, what cells and
functions of the immune system would be deficient? Explain
A child lacking a thymus would have no functional T cells. Without helper
T cells to help activate B cells, the child would be unable to produce antibodies
against extracellular bacteria. Furthermore, without cytotoxic T cells or helper
T cells, the child’s immune system would be unable to kill virus-infected cells
Treatment of antibodies with a particular protease clips
the heavy chains in half, releasing the two arms of the
Y-shaped molecule. How might the antibodies continue
to function?
Since the antigen-binding site is intact, the antibody fragments could neutralize
viruses and opsonize bacteria.
Suppose that a snake handler bitten by a particular venomous snake species was treated with antivenin.
Why might the same treatment for a second such bite have a
harmful side effect?
If the handler developed immunity to proteins
in the antivenin, another injection could provoke a severe immune response
HIV infects helper T cells with high efficiency by binding
specifically to the CD4 accessory protein. HIV also infects some cell types that have low levels of CD4,
such as macrophages and brain cells.
An epitope associates with which part of an antigen receptor
or antibody?
(A) the tail
(B) the heavy-chain constant regions only
(C) variable regions of a heavy chain and light chain combined
(D) the light-chain constant regions only
C. variable regions of a heavy chain and light chain combined
Which statement best describes the difference between responses
of effector B cells (plasma cells) and those of cytotoxic T cells?
(A) B cells confer active immunity; cytotoxic T cells confer
passive immunity.
(B) B cells respond the first time a pathogen is present;
cytotoxic T cells respond subsequent times.
(C) B cells secrete antibodies against a pathogen; cytotoxic
T cells kill pathogen-infected host cells.
(D) B cells carry out the cell-mediated response; cytotoxic
T cells carry out the humoral response.
(C) B cells secrete antibodies against a pathogen; cytotoxic
T cells kill pathogen-infected host cells.
Which of the following statements is true?
(A) An antibody has one antigen-binding site.
(B) A lymphocyte has receptors for a single antigen.
(C) Every antigen has a single epitope.
(D) A liver or muscle cell makes two classes of MHC molecule.
(B) A lymphocyte has receptors for a single antigen.
Which of the following should be the same in identical twins?
(A) the set of antibodies produced
(B) the set of MHC molecules produced
(C) the set of T cell antigen receptors produced
(D) the set of immune cells eliminated as self-reactive
(B) the set of MHC molecules produced
Vaccination increases the number of
(A) different receptors that recognize a pathogen.
(B) lymphocytes with receptors that can bind to the pathogen.
(C) epitopes that the immune system can recognize.
(D) MHC molecules that can present an antigen.
(B) lymphocytes with receptors that can bind to the pathogen.
Which of the following is least likely to help a virus avoid
triggering an adaptive immune response?
(A) having frequent mutations in genes for surface proteins
(B) infecting cells that produce very few MHC molecules
(C) producing proteins very similar to those of other viruses
(D) infecting and killing helper T cells
(C) producing proteins very similar to those of other viruses
The B cell typically releases ___ during the humoral response. In contrast, a T cell will release ____ during cell-mediated response
B cell antiBodies
T cell cyTokines
True or False: in both B and T cells, their receptors will leave as antibodies
False, only B cell receptors will leave as a an antibody
T cells require presentation of a pathogen by the ____ protein. In contrast, B cells
MHC1
B cells don’t require presentation and can bind to free floating antigens
Which of the following would prevent a pathogen from
entering the body?
a. The complement system of proteins
b. An inflammatory response
c. Phagocytic cells
d. Lymphocytic cells
e. None of the above
None of the above
If a person were unable to initiate any aspect of the
inflammatory response, which of the following defenses would
NOT be lost as a result? (I.e. what could this person’s immune
system still do)
a. Ingest any of the pathogens at the site of entry into the body’s tissue.
b. Recruit monocytes (macrophages) from the blood to the tissue.
c. Recruit neutrophils from the blood to the tissue.
d. Bring large amounts of complement proteins from the blood to the tissues.
e. There are no exceptions.
A
Consider a cell which has a viral peptide being presented in its MHC I.
From that information and that information alone we know:
a. The cell is a nucleated cell.
b. The cell must be a professional antigen-presenting cell (APC).
c. The cell has been infected with a virus.
d. Two or more of the above.
e. None of the above.
C and A
Consider a situation in which a memory CD4 cell binds to a
dendritic cell (DC) in a lymph node via its T Cell Receptor (TCR).
Which of the following is most likely false?
a. New memory CD4 cells will be generated as a result of the binding.
b. New effector CD4 cells will be generated as a result of this binding,
c. Smaller numbers of effector CD4 cells will be generated than when this
antigen was encountered initially.
d. Memory B cells will be able to get activated (and undergo clonal expansion)
by an activated descendant of this memory CD4 cell.
e. New effector CD4 cells will be activated in a shorter period of time than
when this antigen was encountered initially.
Smaller numbers of effector CD4 cells will be generated than when this
antigen was encountered initially.
Consider a pathogen which can exist and entirely complete its
replication cycle outside of a host cell (i.e. extracellularly). Given
that information, which of the following statements is the most
likely to be TRUE?
a. The specific immune response will not get activated by this pathogen.
b. The non-specific immune response will not be initially involved in fighting
this pathogen.
c. The cellular arm (cytotoxic T cells) of the specific immune response will be
chiefly responsible for fighting this pathogen.
d. The humoral arm (B cells) of the specific immune system will be chiefly
responsible for fighting this pathogen.
e. There is more than one correct answer choice.
d. The humoral arm (B cells) of the specific immune system will be chiefly
responsible for fighting this pathogen.
Compare MHC1 to MHC2
MHC I - a complex that is present on the surface of ALL nucleated cells in mammals. Nucleated cells are required to present samples of the proteins they are producing in their MHC I complexes. This presentation allows our cells to be checked for infection by CD8 T cells.
● MHC II - a complex that is only present on phagocytic cells, which are also referred to as APCs or “professional antigen
presenting cells”. APCʼs travel throughout the lymphatic system presenting samples of the
pathogens they have phagocytosed to CD4 T cells
Any nucleated cell without MHC I present on its surface will be ____
flagged
TorF:As a result, a normally functioning APC should only ever present foreign (pathogenic or viral) peptide in its MHC II.
True
CD8 cells are responsible for ___
while CD4 cells are responsible for___
CD8 checks for infection in nucleated cells presented by MHC 1 complexes
CD4 is presented with phagocytosed pathogens from APCs
An APC or professional antigen presenting cell is…
a phagocytic cell like macrophages, neutrophils, and dendritic. They only ever present foreign material in their MHC2
Compare Helper T cells to Cytotoxic T cells.
Helper T cell -has a CD4 co-receptor, capable of interacting with MHC II complexes, can release cytokines to activate
APCs, B cells, and/or CD8 T cells, cannot neutralize any pathogens itself. These are also sometimes referred to as CD4 T cells.
Cytotoxic T cell -a CD8 co-receptor, capable of interacting with MHC I complexes, is activated (turned on) by Helper
T cells, can release perforin and granzymes to kill infected cells once activated. These are also sometimes referred to as CD8 T cells.
PRRs are
receptors on the surface of INNATE immune system cells. Hihgly specific but not unique, each innate immune system cell will have these receptors. They recognize patterns and molecules not found in mammals like flagella or 2xRNA
Two different viruses encounter a type of human cell that both viruses have specificity for. You can be sure:
a. Both viruses will use the the same receptor on the cell surface to enter the cell
b. If one of the viruses has an envelope surrounding it, it will fuse with a membrane of the cell
c. at least on of the viruses will replicate inside an endosome
d. at least on of the viruses is enveloped by a lipid membrane envelope
e. both viruses have the same nucleic acid as their genome
b. If one of the viruses has an envelope surrounding it, it will fuse with a membrane of the cell
Which of the following statements about viruses is false?
a. a viral particle coated by bound antibodies may wind up inside a macrophage
b. an enveloped viral particle may be bound by complement proteins
c. a viral particle found outside a host cell will not be in the process of replicating its genome
d. a viral particle that has mutated its envelope glycoproteins may not be recognized by the host’s immune system during a secondary response
e. There are no false statements above
e. There are no false statements above
Which statements regarding bacterial defenses against phages is false?
a. natural selection can play a role in bacterial defenses
b. CRISPR-Cas is a bacterial immune system that cannot be triggered the first time a bacterium is exposed to a particular phage
c. a bacterium can utilize restriction enzymes to cut up foreign DNA but in doing so, they destroy their own genetic material
d. within CRISPR-CAs, the newest viral sequence is always integrated at the 5’ end of the locus
e. there are not false statements provided
c. a bacterium can utilize restriction enzymes to cut up foreign DNA but in doing so, they destroy their own genetic material
An uninfected macrophage would be expected to do all of the following except
a. present a peptide in its MHC1
b. release cytokines
c. present a foreign peptide in it MHC2
d. Activate a CD8 cell
e. there is more than one exception
f. there are no exceptions
D. activate a CD8 cell
Consider a liver cell presenting self-peptide in its MHC1. Which of the following would be a reasonable conclusion to make about the cell based off of this information
a. it is likely that the liver cell will be activated by a CD4 Helper T cell
b. the liver cell is infected
c. The liver cell will be targeted for death by an activated CD8 Cytotoxic T cell
d. The liver cell will be ignored by the cells of the specific immune system
e. More than one above
d. The liver cell will be ignored by the cells of the specific immune system
Which of the following statements accurately describes B and T cells?
a. BCRs have dual specificity and are able to find two structurally different epitopes
b. A single B cell receptor can only bind to one specific epitope, while a single TCR can bind to two epitopes simultaneously
c. The variable antigen binding regions of BCRs and TCRs are created through recombination of different gene segments
d. Both B and T cells release soluble proteins with the same specificity as their antigen receptor upon activation
e. more than one above
c. The variable antigen binding regions of BCRs and TCRs are created through recombination of different gene segments
The complement system is
a. set of proteins involved in innate but not acquired immunity
b. a set of proteins secreted by cytotoxic T calls and other CD8 cells
c. A group of proteins that includes interferons and interleukins
d. a group of antimicrobial proteins that act together in a cascade fashion
e. a set of proteins that act independently to attack and lyse microbes
d. a group of antimicrobial proteins that act together in a cascade fashion
Inflammatory responses typically include
a. clotting proteins migrating away from the site of infection
b. increased activity of phagocytes in an inflamed area
c. reduced permeability of blood vessels to conserve plasma
d. release of substances to decrease the blood supply to an inflamed area
e. inhibiting the release of white blood cells from bone marrow
b. increased activity of phagocytes in an inflamed area
Positive selection refers to
a process that must be undergone by both CD4 and CD8 cells, but not B cells. It is a complex process that generates short lived CD4/8 cells to long lived.
Naive CD8 cells can _____ while activated CD8 cells can ___
can only be activated by an activated CD4
Could kill a cell presenting foreign peptide in its MHC1
