what is the term used for the ability of some microbes to alter their surface molecules and evade destruction by the hosts antibodies
antigenic variation
which statement is false
coagulase destroys blood clots
are exotoxins more potent than endotoxins
yes
are endotoxins gram positive or gram negative
gram negative
the visible signs of viral infections
cytopathic effects
baceterial iron binding proteins
siderophores
is staphylococcal enterotoxin produced by staphylococcus aureus growing in the host intestines
no
which of the following statements about M protein in false
it is readily digested by phagocytes
polio is transmitted by ingestion of water contaminated with feces containing polio virus. What portal of entry does polio virus use?
mucous membranes only
all of the following bacteria release endotoxin except
clostridium botulinum
endotoxins in sterile injectable drugs could cause
septic shock symptoms
in general LD50 for exotoxins is much greater than the LD50 for endotoxins
false
the M protein enhances the virulence of streptoccus by preventing phagocytosis
true
In AB exotoxins, ,the A component binds to the host cell receptor so that the B component can enter the cell
false
most symptoms of endotoxins can be treated with administration of anti-endotoxin antibodies
false
infections with some viruses may induce chromosomal changes that alter the growth properties of host cells
true
many pathogens use the same portal for entry an exit from the body
true
Which of the following statements concerning antigen-presenting cells is true?
They are involved in activating T cells.
What is the correct sequence of events for activation of a B cell by a T-dependent antigen?
(1) Immunoglobulin receptors on the B cell recognize and bind the antigen. (2) An antigen fragment in complex with MHC class 2 is displayed on the B cell's surface. (3) The MHC-antigen complex binds a receptor on a TH cell. (4) The TH cell secretes cytokines that activate the B cell.
If a patient has been exposed to an antigen for the first time, which class of immunoglobulin appears first?
IgM
Which type of cell directly attacks infected cells?
Cytotoxic T-cells
Immune cells that secrete cytokines and activate other immune cells are:
Helper T-cells
HIV directly infects T-cells. Why is this problematic for cell-mediated immunity?
Cytotoxic T-cells begin to attack the virally infected T-cells, reducing the number of T-cells in the body
How do helper T-cells and cytotoxic T-cells work together?
Helper T-cells produce cytokines to activate other cells of the immune system.
Which of the following statements concerning cellular immunity is FALSE?
Cellular immunity involves cells that recognize antigens and make specific antibodies against them.
An individual may be exposed to a pathogen and become infected without actually getting sick. This is known as a subclinical infection. Even in subclinical infections, the individual's adaptive immune system can generate memory for the pathogen. What type of adaptive immunity is this?
naturally acquired active immunity
Where are MHC molecules located on a cell?
On the surface of the cell
What is a feature of the small fragments presented by MHC-I proteins?
They are small peptides, roughly 8-10 amino acids long.
Which organelle assists directly with the presentation of MHC-I antigens?
The endoplasmic reticulum
When does MHC-II loading occur?
During the fusion of vesicles containing MHC-II proteins with vesicles containing digested pathogens
Which of the cells listed below can present antigens on Class II MHC proteins?
Macrophages
What is apoptosis?
The process of programmed cell death.
What is the function of the CD8 receptor?
Bind to MHC molecules
What is the fate of activated cytotoxic T-cells?
They proliferate into a clone of cells specific to the same antigen; some of these cells then differentiate into long-lived memory T-cells, while others mature to attack infected cells.
Which molecule triggers apoptosis?
Granzyme
Which event happens first during cytotoxic T-cell activation?
CD8 binds to MHC molecules of infected cells
Which receptor on the helper T-cell recognizes the specific antigen from an antigen-presenting cell?
TCR
TH2 cells produce cytokines that activate
B cells.
Which proteins on the antigen-presenting cell are recognized by the helper T-cell?
MHC proteins
When do helper T-cells develop into TH1 or TH2 cells?
After proliferation into a clonal population
Natural killer cells are activated by
TH1 cells.
What type of immunity results from vaccination?
artificially acquired active immunity
Newborns' immunity due to the transfer of antibodies across the placenta is an example of
naturally acquired passive immunity.
Which of the following statements is NOT a possible outcome of antigen-antibody reaction?
clonal deletion
When an antibody binds to a toxin, the resulting action is referred to as
neutralization.
The specificity of an antibody is due to
the variable portions of the H and L chains.
Which of the following is NOT a characteristic of B cells?
They recognize antigens associated with MHC I.
Plasma cells are activated by a(n)
antigen.
The antibodies found in mucus, saliva, and tears are
IgA.
The antibodies found on the surface of B cells, and which always exist as monomers, are
IgD.
In addition to IgG, the antibodies that can fix complement are
IgM
The most abundant class of antibodies in serum is
IgG.
Memory cells do not require B cell receptors.
False
Plasma cells will eventually differentiate into memory cells.
False
The variable region of the antibody is solely responsible the significant diversity of antigen targets.
False
Only dendritic cells produce interleukins.
False
Cytokines are protein-based chemical messengers that allow for communication between cells of the immune system.
True
IL-2, produced by TH cells,
stimulates TH cell maturation
Which of the following statements about natural killer cells is FALSE?
They are stimulated by an antigen.
The following events occur in cellular immunity. What is the third step?
TH cell produces cytokines.
Dendritic cell takes up antigen.
TH cells proliferate.
Antibodies are produced.
Antigen enters M cell.
TH cells proliferate.
Which of the following destroys virus-infected cells?
CTL
Which of the following bacterial components would most likely result in B cell stimulation by T-independent antigens?
capsule
In the figure, what can attach to a host cell?
a and c
b and c
b
a and d
e
e
Which of the following statements is FALSE?
The constant region of a heavy chain is the same for all antibodies.
In the figure, the arrow at time (c) indicates
the secondary response.
Which of the following is the best definition of antigen?
a chemical that elicits an antibody response and can combine with these antibodies
The following events elicit an antibody response. What is the third step?
TH cell recognizes antigen-digest and MHC II.
In the figure, which areas are similar for all IgG antibodies?
c and d
Which of the following is not a mechanism used by pathogens to avoid phagocytosis?
causing the release of the lysosome contents inside the phagocyte, killing it
attacking the phagosome, allowing the pathogen to reproduce inside the phagocyte
destroying the pseudopods to prevent ingestion by the phagocyte
preventing the formation of the phagolysosome
destroying the pseudopods to prevent ingestion by the phagocyte
the dermis is composed of connective tissue and provides protection from the external environment
true
the inflammatory response can only be trigged by an infection
false
histamine and kinins cause increased blood flow and capillary permeability
true
ingestion of certain lactic acid bacteria has been show to be beneficial for function and health of the intestinal tract
true
which of the following cells is not an APC
natural killer cells
which of the following is not a characteristic of cellular immunity
it can inhibit the immune response
the antibodies that can bind to large parasites are
IgE
What are the large antibodies that agglutinate antigens
IgM
an antibody's Fc region can be bound by
macrophages
cytokine storms negatively impact human health
true
which of the following is found normally in serum
complement
which of the following is not a membrane disrupting toxin
ab toxin