bio exam 4

Which of the following statements is true?

A lymphocyte has receptors for a single antigen. Submit

Select the correct statement about the immune system.

All antigen receptors produced by a single B cell or T cell are identical and bind to the same epitope. Submit

Which option best describes how a viral antigen, like EBV, is recognized by T cells?

An antigen fragment is presented within class I MHC to the T cell receptor.

How does an antihistamine reduce allergy symptoms?

An antihistamine blocks receptors for inflammatory chemicals released from granules within mast cells.

Which secretion is not a barrier that prevents pathogens from entering the body?

Antigens

Which of the following statements about the clonal-selection theory of immune system function is false?

Antigens are recognized by receptor proteins inside the lymphocyte.

Because antigen receptor genes are randomly rearranged, some immature lymphocytes produce receptors specific for epitopes on the organism's own molecules. Why doesn't the immune system attack these molecules on the body's cells and tissues?

B and T cells with receptors specific for the body's own molecules are destroyed by apoptosis. Submit

Clonal selection is the division of _____ that have been stimulated by binding to an antigen, which results in the production of cloned _____.

B cells ... plasma cells and memory cells

Which statement best describes the difference between responses of effector B cells (plasma cells) and those of cytotoxic T cells?

B cells secrete antibodies against a pathogen; cytotoxic T cells kill pathogen-infected host cells.

Each person makes more than 1 million different B cell antigen receptors and more than 10 million different T cell antigen receptors. How is such diversity in antigen receptors generated?

By combining variable elements, the immune system assembles many different receptors from a much smaller collection of parts.

How are cytotoxic T lymphocytes (CTLs) produced?

CD8+ T cells divide and differentiate into cytotoxic T lymphocytes.

What is the final step in the cell-mediated response to a viral infection?

Cytotoxic T lymphocytes punch holes in the membranes of infected host cells.

A C. diff outbreak occurs in a nursing home. Which of the following would likely be best to stop the outbreak?

Disinfect all areas for spores.

What is the role of recombinase in generating lymphocyte diversity?

Early in B cell development, recombinase links one light-chain V gene segment to one J gene segment.

A man who has been exposed to the flu virus is tested by his physician. The physician notes that the virus is present but no measurable level of antibodies corresponding to the virus are detected in his body.

He was probably exposed a few days ago and clonal selection has yet to produce plasma cells.

How do cells involved in the humoral response respond to antigen presentation on the surface of a B cell?

Helper T cells recognize the receptor-antigen complex and cause plasma and memory cells to be produced to then produce antibodies.

Vertebrate immune cells, which are phagocytic, include which of the following? I) neutrophils II) macrophages III) dendritic cells IV) natural killer cells

I, II, and III

Which of the following statements describe a component of the clonal selection theory of how the adaptive immune system functions? I) Each lymphocyte has a unique membrane receptor that recognizes one antigen .II) When the lymphocyte binds an antigen, it is activated and begins dividing to form many identical copies of itself. III) Cloned lymphocytes have slight differences and are selected by the spleen for removal if they do not bind an antigen. IV) Cloned cells descend from an activated lymphocyte and persist even after the pathogen is eliminated.

I, II, and IV

Which of the following are similarities between B cells and T cells? I) Both recognize antigens using immunoglobulin receptors. II) Both undergo clonal selection after encountering an antigen. III) Both maintain an immunological memory of previously encountered antigens.

II & III

Which statement is true about innate immunity?

Innate immunity is the first, and most general, mechanism of protection against pathogens.

Which answer describes an advantage of having a system of adaptive immunity?

It enables a rapid defense against an antigen that has been previously encountered.

How do cells involved in the innate immune response detect the presence of pathogens?

Leukocytes recognize unique molecules on pathogens.

Tissues are immunologically "typed" before an organ transplant to make sure that the donor and recipient match as closely as possible in their __________.

MHC (major histocompatibility complex) proteins

Which protein presents viral antigens on the outer surface of cells?

MHC protein.

Which of the following cells can engulf a pathogen?

Macrophages

Which of the following events occurs first when a wound that breaks the skin has occurred?

Platelets release proteins that form clots and decrease bleeding.

Which of the following statements about epitopes is incorrect?

There is a one-to-one correspondence between antigen and epitope.

Which is a true statement about memory cells?

They have a longer lifespan than plasma cells. Submit

Which of the following statements best describes the role of mast cells in the inflammatory response?

They release chemicals that dilate blood vessels near the wound site, allowing blood components to enter the region from the bloodstream.

You and your friend were equally exposed to a virus, but over the next few days, only your friend acquired flu-like symptoms and was ill for almost a week before recovering. Which one of the following is a logical explanation for this?

You had an immunological memory of that virus.

You are a doctor. A patient presents with diarrhea and tests positive for C. diff. Which of the following is true?

Your patient may or may not have recently taken antibiotics.

Which statement correctly describes the complement system?

a group of proteins that act together in a cascade fashion

Which response is triggered when bacteria enter the body through a small cut in the skin?

activation of a group of proteins called complement

Which of these is absent from insect immunity?

activation of natural killer cells

Which statement best describes the concept of clonal selection?

an antigen can provoke production of high amounts of specific antibodies

A patient has a high level of mast cell activity, dilation of blood vessels, and acute drop in blood pressure. Which condition is most consistent with these symptoms?

anaphylactic shock immediately following exposure to an allergen

Extracellular pathogens such as viruses and bacteria in body fluids are attacked by __________.

antibodies

An organism that lacks their thymus would ________.

be unable to differentiate and mature T cells

The role of active cytotoxic T cells is to attack __________.

body cells that have been infected

What is the function of reverse transcriptase?

catalyzing the formation of DNA from a RNA template

Helper T cells are part of __________.

cell-mediated immune responses

Which of the following can trigger septic shock?

certain bacterial infections

Innate immunity and adaptive immunity are both __________.

characteristics of all vertebrate animals

Which of the following components of the immune system destroys cancer cells by forming holes in plasma membranes and triggering apoptosis?

cytotoxic T cells

T cells of the immune system include ________.

cytotoxic and helper cells

The number of major histocompatibility (MHC) protein combinations possible in a given population is enormous. However, an individual in the population has a far more limited array of MHC molecules because ________.

each of the MHC genes has a large number of alleles, but each individual only inherits two for each gene Submit

The words "antigen" and "virus" are interchangeable.

false

True or false? The leukocytes of the innate immune system are B cells, macrophages, and neutrophils.

false

B cells are stimulated to differentiate under which of the following conditions?

helper T cells release cytokines

What is the source of a viral envelope?

host cell membrane

_____ interact with the antigen-class II MHC complex presented by macrophages.

hyper t cells

Which of the following are typical features of an inflammatory response?

increased activity of phagocytes in an inflamed area

A boy falls while riding his bike. A scrape on his hand almost immediately begins to bleed and becomes red, warm, and swollen. Which type of response is most consistent with these symptoms?

inflammatory response

Which treatment could relieve the symptoms of an individual who has been bitten by a poisonous snake that has a fast-acting toxin?

injection of antibodies to the toxin

Acidity in human sweat is part of which type of immune system?

innate immunity

A nonfunctional CD4 protein on a helper T cell would result in the helper T cell being unable to ________.

interact with a class II MHC-antigen complex

An antigen

is a molecule that evokes an immune response by a lymphocyte

While working as a microbiologist, you discover a new species of Clostridium. Which of the following is true?

it is most likely harmless

Macrophages are

large, phagocytic cells that can leave circulation and enter the tissues of the body

Vaccination increases the number of

lymphocytes with receptors that can bind to the pathogen

Which of these cells is a phagocytic leukocyte that can engulf a foreign bacterium?

macrophage

Which of the following cells and signaling molecules are involved in the initial stages of the inflammatory response?

mast cells and histamines

Which of these is a characteristic of adaptive immunity but not innate immunity?

memory

A certain cell type has existed in the blood and tissue of its vertebrate host's immune system for over 20 years. One day, it recognizes a newly arrived antigen and binds to it, subsequently initiating a secondary immune response in the body. Which of the following cell types most accurately describes this cell?

memory cell

Which of these cells is responsible for the rapidity of the secondary immune response?

memory cells

Which statement correctly describes both CD4 and CD8 proteins?

molecules present on the surface of T cells that interact with major histocompatibility (MHC) molecules

The primary reason for needing a new vaccine for influenza each year is that __________.

mutation in the influenza virus is frequent

Which of the following components make up a light chain of an immunoglobulin (Ig) molecule, of any class, with regions symbolized as C or V, H or L?

one C region and one V region

Which of the following enhances phagocytosis of microbes by macrophages? I) the binding of antibodies to the surface of microbes II) antibody-mediated opsonization of microbes III) the release of cytokines by activated B cells

only I and II

Lymphocytes mature in the ________.I) spleen II) thymus I) bone marrow

only II and III

Breast feeding confers which type of immunity to an infant?

passive immunity

The role of cytotoxic T cells is the secretion of _____, which plays a role in the _____ immune response.

perforin ... cell-mediated

Which of the following can result in naturally acquired passive immunity?

placental transfer of antibodies

B cells that have been stimulated by interleukin-2 develop into _____.

plasma cells

Which of these cells produce and secrete antibodies?

plasma cells

Which of the following is crucial to activation of the adaptive immune response?

presentation of MHC (major histocompatibility complex)-antigen complex on a cell surface

Which of the following is least likely to help a virus avoid triggering an adaptive immune response?

producing proteins very similar to those of other viruses Submit

Double-stranded viral DNA is incorporated into a host cell as a _____.

provirus

Yearly vaccinations for influenza viruses are necessary for humans because ________.

rapid mutation in flu viruses alters the surface proteins in infected host cells

Within a differentiated B cell, the activity of which molecule results in the rearrangement of DNA sequences between variable regions and joining regions?

recombinase

The fact that there are about a million different antigen receptors possible in human B cells is based on __________.

recombination of the DNA segments that make up the functional receptor genes of differentiated B cells

Clonal selection and differentiation of B cells activated by antigen exposure leads to the production of ________.

short-lived plasma cells that secrete antibodies for the antigen

The genetic material of HIV consists of _____.

single stranded RNA

Which statement best describes what causes the clumping of antigens when antibodies bind antigens?

the antibody has two identical binding sites

Which of the following components of the immune system is most likely to be the same in identical twins?

the kinds of major histocompatibility (MHC) molecules produced

Which statement best describes an account of immunological memory?

the observation that someone who had recovered from the plague could safely care for those newly diseased

Which of the following protects both the eyes and the respiratory tract against infections?

the secretion of lysozyme onto their surfaces

Which of the following should be the same in identical twins?

the set of MHC molecules produced

Which of the following best explains why a bone marrow transplant may not be appropriate from a given donor to a given recipient even though they are compatible for blood transfusions?

their blood-types may match but major histocompatibility (MHC) proteins may not be a match

Which option best describes why Jenner's use of cowpox virus as a vaccine against the smallpox virus was successful?

there are some epitopes (antigenic determinants) common to both pox viruses

Cell-mediated immunity differs from humoral immunity in that __________.

they respond differently to invaders

Which structure is not a component of the adaptive immune system?

tissues

Mucus occurs in both the respiratory and digestive tracts. Which answer best describes the main immunological function of mucus?

to physically trap pathogens

Which of the following are molecules on mammalian cells that recognize macromolecules that are present in or on certain groups of pathogens?

toll-like receptors

What is the major method of transmission of infectious disease when using public transportation?

touching surfaces that sick people have touched

Vaccination offers protection against future exposure to pathogens because it ________.

triggers clonal expansion of lymphocytes

The site of inflammation may become swollen due to the increased numbers of cells and fluids at the site and painful due to signals from pain receptors.

true

True or false? B cells were originally isolated from the bursa in chickens, and their function is to produce antibodies; T cells were originally isolated from the thymus in mice, and their functions include killing host cells that are being infected with a virus.

true

An epitope associates with which part of an antigen receptor or antibody?

variable regions of a heavy chain and light chain combined

A strain of fruit fly lacks the ability to produce Dicer-2 protein will most likely be susceptible to which of the following types of infections?

viral