Final Chapter 43 Bio102

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.

How does an antihistamine reduce allergy symptoms?

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

If a patient is missing B and T cells, what would be absent from the immune response?

memory

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

they respond differently to invaders

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.

Which of the following pairs of proteins shares the most overall similarity in structure?

B-cell receptors and antibodies

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.

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.

Arrange in the correct sequence these components of the mammalian immune system as it first responds to a pathogen. I) Pathogen is destroyed. II) Lymphocytes secrete antibodies. III) Antigenic determinants from pathogen bind to antigen receptors on lymphocytes. IV) Lymphocytes specific to antigenic determinants from pathogen become numerous. V) Only memory cells remain.

III → IV → II → I → V

What major advantage is conveyed by having a system of adaptive immunity?

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

Tissues are immunogically "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 of the following is a difference between B cells and T cells?

One has a major role in antibody production, while the other has a major role in cytotoxicity.

Clonal selection is an explanation for how _____.

an antigen can provoke production of high levels of specific antibodies.

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

antibodies from plasma cells

A newborn who is accidentally given a drug that destroys the thymus would most likely _____.

be unable to differentiate and mature T cells.

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

body cells that have been infected

Helper T cells are part of _____.

cell-mediated immune responses

The EBV antigen fragments will be presented by the virus-infected cells along with _____.

class I MHC molecules.

Which of the following components of the immune system destroys bacteria in a way similar to an antitank weapon destroying armored military tanks by punching holes in the wall of the bacteria?

complement protein

An individual who has been bitten by a poisonous snake that has a fast-acting toxin would likely benefit from _____.

injection of antibodies to the toxin

An antigen _____.

is a foreign molecule that evokes a specific response by a lymphocyte

Vaccination increases the number of _____.

lymphocytes with receptors that can bind to the pathogen.

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

memory cell

A primary reason for needing a new vaccine for influenza each year is that _____.

mutation in the influenza virus is frequent

An immunoglobulin (Ig) molecule, of whatever class, with regions symbolized as C or V, H or L, has a light chain made up of _____.

one C region and one V region.

Which of the following statements about epitopes are correct? I) B-cell receptors bind to epitopes. II) T-cell receptors bind to epitopes. III) There can be 10 or more different epitopes on each antigen. IV) There is a one-to-one correspondence between antigen and epitope.

only I, II, and III

Which of the following statements are fundamental to 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.

only I, II, and IV

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

only II and III

What type of immunity is associated with breast feeding?

passive immunity

Naturally acquired passive immunity can result from the _____.

placental transfer of antibodies

Yearly vaccination of humans for influenza viruses is necessary because _____.

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

Within a differentiated B cell, the rearrangement of DNA sequences between variable regions and joining regions is accomplished by a(n)_____.

recombinase

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

recombination of the segments of the receptor DNA 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.

Immunological memory accounts for _____.

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

When antibodies bind antigens, the clumping of antigens results from _____.

the antibody having at least two binding regions

The switch of one B cell from producing one class of antibody to another class of antibody that is responsive to the same antigen is due to _____.

the rearrangement of immunoglobulin heavy-chain C region DNA

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

the set of major histocompatability (MHC) molecules produced

For the successful development of a vaccine to be used against a pathogen, it is necessary that _____.

the surface antigens of the pathogen stay the same

Jenner's successful use of cowpox virus as a vaccine against the smallpox virus was due to the fact that _____.

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