BIOS EXAM 4

Which of the following is used to classify viruses? i. Nucleic acid ii. Shape iii. Size iv. Host range v. Biochemical tests

(i), (ii), (iii), and (iv)

"Clonal selection" and "clonal expansion"

- imply that each individual lymphocyte produces a single antibody - describe how a single lymphocyte proliferates in a population of effector cells - depend on an antibody recognizing a specific epitope - explain how an antigen stimulates the production of matching antibodies

A physician is attempting new therapies for HIV patients who are suffering from an impaired immune response. He decides to try using a recombinant form of colony-stimulating factor cytokine (CSF). Why

CSF will help to stimulate the production of new lymphocytes, the very cells that are affected by HIV. This may help to keep the patients' immune responses "normal" for a period of time.

Antibodies are made by

B cells and plasma cells

Select the ways that plant viruses can infect plants.

By contaminated insects feeding on plant cells and disrupting the cell wall. By soil that was previously used to grow infected plants. Through grafting infected plant tissue onto healthy tissue.

Formation of large Ab-Ag complexes as a result of the Ab binding two separate antigens

Cross-linking

Which step/component of phagocytosis is/are affected by the genetic defect causing CGD?

D

Which of the following statements about normal microbiota is FALSE?

Disruption of the normal microbiota has little effect on the host.

What are two ways that phage can replicate without directly lysing their host cell?

Extrusion and lysogeny

Why does Aggregibacter actinomycetemcomitans synthesize leukotoxin A?

For self-defense—the toxin protects the bacterium against phagocytes such as neutrophils.

Which of the following contribute to antibody diversity?

Gene rearrangement, imprecise joining AND combinatorial associations

Transduction resulting from a packaging error.

Generalized transduction.

Why are viroids resistant to nucleases?

Having a circular RNA "genome," they are resistant to most exonucleases (that digest the free ends of RNA or DNA).

In opsonization with IgG, why would it be important that IgG react with the antigen BEFORE a phagocytic cell recognizes the antibody molecule?

If the IgG is bound to the phagocyte BEFORE opsonization, it would most likely be ingested by the phagocyte before it could bind to a pathogen (it would be "naked," so to speak).

Which of the following class of antibody is primarily found in external secretions?

IgA

The only class of antibody that can cross the placenta is ______.

IgG

Which class of antibody accounts for most of the circulating antibodies?

IgG

Which of the following antibodies is a pentamer?

IgM

Antibodies bind to flagella preventing movement or to pili preventing attachment of bacteria

Immobilization and prevention of adherence

It would be useful if antigens were delivered directly to

Peyer's patches AND M cells.

The family to which the Rhinovirus belongs is the

Picornaviridae.

Which of the following statements about plant virus transmission are TRUE?

Plant viruses enter their host through wounds. Grafted plants may be at risk of virus infection. An insect may transmit viruses between plants. Parasitic fungi may transmit plant viruses.

What type of programmed cell death also triggers an inflammatory response, recruiting various components of the immune system to the region?

Pyroptosis

In which of the following sites would you expect to find normal microbiota?

Skin, vagina, colon

How do some pathogens prevent complement activation or avoid the effects of activated complement?

Some pathogens hijack the host's regulatory membrane proteins that inactivate C3b, preventing the triggering of the alternative activation pathway AND some pathogens produce C5a peptidase that destroys complement C5a, a chemoattractant that recruits phagocytes to the area of infection.

CD8 cells are

T cytotoxic cells

The receptors found on the T cell in the figure are

T-cell receptors and CD8 proteins

One of the most intensively studied virulent phages which infects E. coli is ______

T4

Please select the TRUE statement regarding Toll-like receptors (TLRs).

TLRs allow cells to detect patterns associated with microbes, indicating that the innate immune responses involve some specificity (although not the specificity of adaptive immunity).

Select all of the statements that apply to a primary response to a T-dependent antigen:

Takes 10-14 days to build a substantial amount of antibodies in the bloodstream. Produces mainly IgM antibodies, but undergoes class switching to other classes near the end of the response. Fine-tunes and increases strength of binding of antibody to antigen through the process of affinity maturation

Smoking impairs the ciliated cells of the middle portion of the respiratory tract. Many analgesic drugs (painkillers) impair peristalsis (the churning motion of the digestive tract). The result of either of these activities leads to an increased risk of infection in their respective areas. Why?

The actions of the cells in these areas help to propel pathogens out of the area, serving as a part of the physical barrier system. When they are impaired/slowed, bacteria and other pathogens have an easier time adhering to the tissues in the area and causing an infection.Correct

Which of the following is the definition of clonal selection?

The process in which a lymphocyte's antigen receptor binds to an antigen, allowing the lymphocyte to multiply.

Why does M. tuberculosis manipulate the macrophage that engulfs it?

To avoid destruction by the macrophage

Please select the methods that are used to cultivate animal viruses.

Use of cell culture techniques. Use of animal inoculation. Inoculation of embryonated eggs.

Please choose the statement that best describes the role of viral surface proteins or spikes.

Viral spikes provide means of attachment to host cell surface.

The humoral immune response is delivered by

antibodies

All of the following events can occur after complement activation except

antibody production

Macrophages and dendritic cells are

antigen presenting cells

Genetic exchange in segmented viruses that allows a zoonotic virus to infect humans is an example

antigenic shift.

The stage of T4 replication that involves interaction between the protein fibers on the phage and receptors on the bacterial cell wall is the

attachment stage

The correct order for the stages of a phage infection is

attachment, penetration, transcription, replication of nucleic acid and protein, assembly, release

Which does not refer to the shape of a virus?

bacillus

Transducing virulent phages do not lyse the cells they invade because

bacterial DNA has replaced critical viral DNA in the phage.

In humans, the stem cells from which all blood cells arise are found in the

bone marrow

Which of the following is a primary lymphoid organ?

bone marrow

Cytotoxic T cells primarily are responsible for

cell-mediated immunity.

Which of the following is a bacterial product?

colicin

Immune complexes activate complement proteins, leading to inflammation and production of MACs

complement system activation

The changes that occur in virally infected cells are characteristic for a particular virus and are referred to as the

cytopathic effect.

The compounds secreted or delivered by the T cell shown in the figure lead to

death of the infected cell. alerting neighboring cells to the presence of virus.

Toll-like receptors

each recognize a specific "danger" molecule AND are embedded in cellular membranes.

Please choose the term that describes a virus that has a lipid bilayer (derived from the host cell) surrounding its capsid.

enveloped virus

Secondary lymphoid organs

facilitate interactions between cells.

Complement factors are named in the order in which they function.

false

One of the strongest indications of infectious disease is

fever

There are ______ class(es) of antibody.

five

The enveloped viruses typically obtain their envelope

from the host cytoplasmic membrane as they exit the host.

The best-known examples of viruses that cause latent infections are

herpes AND chickenpox.

The first host response to a nonspecific tissue injury is described as

inflammation

C3a and C5a are involved in

inflammation AND attraction of phagocytes.

Apoptosis

is a form of programmed cell death AND is induced in target cells by effector T cytotoxic cells.

Allergic reactions mainly involve

mast cells

The term "segmented" refers to viruses that

may contain several pieces of RNA.

Assembly of the T4 phage

may involve some self-assembly AND may involve the use of scaffolds.

Outside of living cells, viruses are

metabolically inert.

The smallest virus is approximately 10 ______ in diameter.

nanometers

Prions affect the

nervous system

Antibodies fill the surface receptors on microbe to prevent attachment to the host

neutralization

The first kind of leukocyte lured to the site of inflammation is the

neutrophil

A medical technician examines a Gram stain of purulent discharge (pus) from a patient with an active infection. Which predominant host cell type will the technician most likely see?

neutrophils

Using phages to treat a bacterial infection is an interesting idea because

of the increasing problem of antibiotic resistance in pathogens.

The variable region of an antibody occurs

on all 4 chains.

Coating of microbe with antibody to enhance phagocytosis

osponization

Spongiform encephalopathy occurs in all of the following EXCEPT

plants

Antibodies are produced by

plasma cells

A limiting factor for viral infection of animals cells is

presence of specific receptor molecules on the host cell.

Only antigen-presenting cells

produce MHC class II molecules.

Interleukins are

produced by leukocytes AND protein molecules.

Toll-like receptors (TLRs) bind molecules on pathogens. This is helpful to the immune response because TLRs

recognize broad categories of molecules that should not be in our system, as we don't have these molecules on our own cells.

Which of the following is a function of the mucociliary escalator?

remove microbes from the respiratory tract

During apoptosis, a cell will

self-destruct without causing an inflammatory response.

Transduction resulting from an error in excision of a prophage.

specialized transduction

Which is not involved in adaptive immunity?

tear flow

If a TC encountered a TH cell infected with a virus,

the TC cell would induce apoptosis in the TH cell.

Antigens interact with antibodies at

the outer end of each arm of the Y.

A _______ is a single virus particle.

virion

Phage that lyses the bacterial host when completing its life cycle.

virulent phage

Opsonization is

when complement enhances phagocytosis of bacterium.

Plant viruses may be transmitted by

worms, contaminated seeds, humans, and insects

IgG molecules attach to a cell targeting it for attack by a NK cell

Antibody-dependent cellular cytotoxicity (ADCC)

Identify the role(s) of natural killer cells.

Antibody-dependent cellular cytotoxicity AND negative selection of lymphocytes that recognize normal "self" molecules AND regulation and direction of certain immune responses.

Check the TRUE statements about fever induction and outcomes.

Fever is induced by cytokines called pyrogens. Fever inhibits bacteria from growing by inhibiting their metabolism. Fever results when macrophages detect microbial invaders and release pro-inflammatory cytokines. Pyrogens have an effect by acting on a certain part of the brain.

Normal tissue taken from animals and prepared immediately as a medium for viral growth is termed a(n)

primary culture.

What is apoptosis?

programmed cell death

In the region of budding, the cytoplasmic membrane acquires

spike proteins AND matrix proteins

In which organism were phagocytes first reported?

starfish larvae

Phage that is able to incorporate its genome into the host chromosome.

temperate phage

Phages that can either replicate and cause cell lysis or can integrate their DNA into the host DNA are called

temperate phages

Most temperate phages integrate into the host chromosome, whereas some replicate as plasmids. Which kind of relationship do you think would be more likely to maintain the phage in the host cell, and why?

Integration, because plasmids are frequently lost during cell division, which could leave a daughter cell without the virus genome. Correct

Which of the following statements about complement protein C1 is FALSE?

It cleaves C3 into C3a and C3b.

Would you expect the number of virions to be the same if you measured them by the plaque assay or by counting using the electron microscope? Why?

No—the plaque assay only measures viable virus particles, while the electron microscope cannot distinguish between defective and viable virus.

Select the TRUE statements regarding reverse-transcribing viruses.

They have a unique enzyme called reverse transcriptase. Their replication strategy goes against the central dogma of genetics. They exhibit high mutation rates in their genomes.

Why is the process of gene rearrangement used in creating antibodies and T-cell receptors (TCRs) so important?

Without it, we would need a single gene for every antibody and TCR required to mount all the possible responses needed during our lives.

Expression of viral oncogenes in infected animal cells

can mimic proto-oncogenes, causing imbalance in cell cycle control towards unchecked proliferation, leading to tumor formation.

The attraction of leukocytes to the area of inflammation is referred to as

chemotaxis

Complement factors C5b+C6+C7+C8 make up a membrane attack complex that results in

cytolysis

During the development of both B and T cells, a process called negative selection occurs. This is necessary because it helps ensure that the cells

do not recognize "self" molecules.

The phages T4 (lytic) and lambda (temperate) share all of the following characteristics EXCEPT

existing as a prophage

Which of the following are most susceptible to complement lysis?

gram - bacteria

Enveloped viruses

have a lipid bilayer membrane containing various proteins.

The surface receptors on B and T cells both

have variable and constant regions.

The low molecular weight protein produced by animal cells in response to viral infections is

interferon.

Giant cells are

used to contain bacterial infections.

How long after initiation of a primary response do significant amounts of antibody appear in the blood?

10-14 days

There are ______ major families of RNA containing viruses that infect vertebrates.

13

Arrange the following events in clonal selection in the correct order: 1. Helper T cells are activated. 2. Macrophages ingest antigen. 3. B cells differentiate into plasma cells and memory cells.

2,1,3

In the case of T-even phages, the burst size is about

200 per host cell

Arrange the following in the proper order in which they first appear in the alternative pathway of complement activation. 1. Factor B 2. Factor D 3. C3

3,1,2

Please select the correct sequence for the steps of phagocytosis: 1. Conditions in the phagosome change, increasing its antimicrobial activities. 2. The phagocytic cell binds microbial invaders and engulfs them, internalizing them in a phagosome. 3. Phagocytic cells are recruited to the site of an injury by chemoattractants. 4. Within the phagolysosome, various factors work together to destroy an engulfed invader. 5. The phagosome fuses with enzyme-filled lysosomes, forming a phagolysosome.

3,2,1,5,4

The time from absorption to release for T-even phage is about

30 minutes.

There are ______ major families of DNA-containing viruses that infect vertebrates.

7

People who have compromised first-line defenses are susceptible to opportunistic pathogens. Which situation would be an example of a compromised first-line defense?

A burn patient who has lost extensive areas of the skin.

Immunity to superinfection (infection of a cell at a later time with a second, identical bacteriophage) is a consequence of lysogeny. Why does this occur?

A repressor produced by the first virus will actively suppress the lytic cycle of the second virus.

Which of the following is required for prion replication?

Abnormal Prion Protein

How does a cytokine function?

It is secreted by a specific cell type and binds to a receptor on target cells causing a signal within that cell that turns on (or off) certain genes to achieve a response.

Which of the following statements about interferon is incorrect?

It prevents the entry of viruses into nearby cells.

Which of the following are considered physical (versus chemical) factors that contribute to the skin and mucous membranes protective role against infection?

Layers of cells Mucociliary escalator Flushing of urinary tract

Which of the following do not induce a strong immune response?

Lipids AND simple sugars.

Which of the following describes a latent viral infection?

Long periods of time with essentially zero viral replication, punctuated by outbreaks of active replication and disease manifestation. Infected individuals are largely non-infectious between outbreak periods.

Which of the following are secondary lymphoid organs (areas where mature lymphocytes become activated)?

Lymph nodes Peyer's patches Tonsils Spleen

Which is a filamentous phage?

M13

Please identify the incorrect definition.

MHC class II—molecules that cells use to present antigen to cytotoxic T cells.

Which of the following statements about phagocytosis is FALSE?

Macrophages die after phagocytosing bacteria, but neutrophils survive.

Which of the following is/are a(n) antigen-presenting cell(s)?

Macrophages, dendritic cells, AND B cells

Select all of the following that apply to a secondary response to a T-dependent antigen:

May take only 2-4 days to build a substantial amount of antibodies in the bloodstream. Produces mainly either IgG or IgA antibodies without shifting to other types. Fine-tunes and increases strength of binding of antibody to antigen through the process of affinity maturation.

The site at which a virus has infected and subsequently lysed the infected cell, releasing its progeny to infect and lyse surrounding cells, thereby forming a "clear zone," is

a plaque.

Infection in which a virus multiplies rapidly and spreads in the host.

acute infection

In a quantal assay, animal viruses are quantified by

administering several dilutions of a virus preparation to a number of animals, cells, or chick embryos, then determining the dilution that infected/killed 50% of the group.

Clusters of differentiation (CD) molecules are important because they

allow us to differentiate between cells that may look identical by microscopy.

The complement pathway that is activated by binding of C3b to cell surfaces is the

alternate pathway

T-independent antigens

include polysaccharides.

The presence of long double-stranded RNA (> 30 bp)

induces synthesis of interferon.

Viruses are best described as _______.

infectious agents

Which of the following is NOT an antimicrobial substance?

keratin

Resistance of some animals to certain viral diseases is based on

lack of specific receptors on the host cell.

The cells primarily involved in all immune responses are the

leukocytes

Which of the following is not typical of an antigen?

low molecular weight

The cells responsible for adaptive immunity are the

lymphocytes

After beta phage infects Corynebacterium diphtheriae and integrates its DNA into the host genome, the bacterium is capable of causing the disease diphtheria. Which term best describes this phenomenon?

lysogenic conversion

The function of the secretory component of the IgA molecule is

to protect IgA from being destroyed by proteolytic enzymes.

Syphilis, an STI, was once treated by intentionally infecting the patient with the parasite that causes malaria, a disease characterized by repeated bouts of fever, shaking, and chills. Why might this treatment cure syphilis?

The effect of driving up the body temperature for periods of time can shut down the temperature-sensitive replication of the bacterium that causes syphilis. This gives the immune system time to eliminate it properly.

You add an unknown phage to a mixture of F+ and F− cells of E. coli and plate out the bacteria. The bacterial colonies that grow are all F−. How can you explain this phenomenon?

The phage bound to a receptor on the sex pilus, and therefore only infected the F+ cells (leaving the F− cells alone).

Which of the following descriptions fits a chronic viral infection?

Characterized by continuous production of low levels of viral particles, potentially even in the absence of active symptoms of disease. The organism is usually still highly infectious during this time.

Phagocytes were first discovered and named by

Metchnikoff

The body's own cells do not trigger the alternative pathway of complement system activation. Why is this?

Molecules in host cell membranes bind regulatory proteins that will inactivate any C3b molecules that attach to the membrane.Correct

Which of the following are referred to as mononuclear phagocytes?

Monocytes and macrophages

An antibiotic is added to a culture of E. coli, resulting in death of the cells. Bacteriophages are then added. Would the phages replicate in the E. coli cells? Why or why not?

No, because the bacteriophages would depend too much on having the active machinery of a living host cell for replication.

Which of the following pattern recognition receptors is/are anchored in the host cell membrane?

TLRs and CLRs

Retroviruses are unique in that they

use RNA as a template to make DNA.