Question 1

What is the physical sign that a person's immune system is involved in the proliferation of T cells in response to an infection?

Accepted Answer

Enlargement of lymph nodes in the region of infection is a physical sign that the immune system is involved in the proliferation of T cells. Lymph nodes are specialized structures that serve as primary sites for activation and proliferation of T cells in response to an infection. Therefore, their enlargement indicates the immune response is activated and T cell proliferation is taking place to fight the infection.

Question 2

What happens to plasma cells after the removal of the original antigenic stimulus?

Accepted Answer

The answer of What happens to plasma cells after the...

Question 3

_________ are pathogens that are capable of stimulating immunity while being genetically crippled so that they are unable to cause disease.

Accepted Answer

Attenuated pathogens are genetically crippled, meaning their virulence has been reduced, making them harmless so that they can stimulate the immune system without causing disease. This is a common approach in the development of live and viral vaccines.

Question 4

Where do dendritic cells go once they have processed antigens and what do they do when they get there?

Accepted Answer

Dendritic cells migrate to the lymph nodes after processing antigens. Once they are in the lymph nodes, they present the processed antigens to T cells, which can then identify and respond to the antigens if they are harmful. In the lymph nodes, dendritic cells differentiate into mature antigen-processing cells to continue presenting antigens to T cells.

Question 5

When an antigen binds to the antibody in the membrane of a B cell,the B cell proliferates and forms a population of B lymphocytes that all make the same antibody.The population of B lymphocytes thus formed is called a(n)_________.

Accepted Answer

When a B cell is activated by an antigen and starts dividing, the resulting population of B lymphocytes that produce identical antibodies is called a clone.

Question 6

How many species of T-cell receptors does each T cell have?

Accepted Answer

Each T cell has only one T-cell receptor on its surface.

Question 7

Some of the activated B cells differentiate into short-lived cells that secrete large amounts of antibodies.Such cells are called __________.

Accepted Answer

Plasma cells are short-lived cells that secrete large amounts of antibodies. They are formed from activated B cells during the humoral immune response.

Question 8

How is the material ingested by dendritic cells fragmented?

Accepted Answer

Enzymes in the cytoplasm of the dendritic cells, such as lysosomal enzymes, are responsible for fragmenting the antigens of the ingested material. This allows the dendritic cells to present the antigens to other immune cells for recognition and activation of an immune response.

Question 9

What subfamily of small cytokines acts primarily as chemoattractants that stimulate the migration of lymphocytes into inflamed tissue?

Accepted Answer

Chemokines act primarily as chemoattractants that stimulate the migration of lymphocytes into inflamed tissue.

Question 10

Who realized that a cowpox infection at an early age protected people against deadly smallpox infections? He had noticed that milkmaids were typically spared the ravages of smallpox.He turned this observation into vaccination by intentionally exposing a boy to cowpox to develop immunity and then later exposing the same boy to smallpox,which he survived.

Accepted Answer

Edward Jenner realized that a cowpox infection at an early age protected people against deadly smallpox infections. He noticed that milkmaids were typically spared the ravages of smallpox and turned this observation into vaccination by intentionally exposing a boy to cowpox to develop immunity and then later exposing the same boy to smallpox, which he survived.

Question 11

When does the full repertoire of antibody-producing cells (all such cells that a person will ever have)appear in the lymphoid tissue?

Accepted Answer

The full repertoire of antibody-producing cells appears in the lymphoid tissue before stimulation by any antigen. This is because during embryonic development, precursor cells give rise to all the different types of lymphocytes, including B cells that produce antibodies. These precursor cells then undergo genetic rearrangements to generate a diverse repertoire of lymphocytes capable of recognizing a wide variety of antigens. Therefore, the full repertoire is present before any exposure to stimuli, such as antigens or antibodies.

Question 12

What is usually required for B cell activation by an antigen?

Accepted Answer

B cell activation by an antigen usually requires the help of T cells, specifically CD4+ T helper cells. These T cells recognize the antigen presented by B cells and provide signals that activate the B cell.

Question 13

Which of the antigens below are typically able to activate B cells without the involvement of T cells?

Accepted Answer

Bacterial cell wall polysaccharides are typically able to activate B cells without the involvement of T cells. This is because they have repetitive epitopes that are recognized by B cell receptors (BCRs). In contrast, the other antigens listed (very large bacterial lipids, very large viral lipids, bacterial cell wall polypeptides, and bacterial DNA) require additional processing and presentation by antigen-presenting cells (APCs) in order to activate T cells, which then help to activate B cells.

Question 14

Why is the second response to an antigen on a pathogen faster than the initial response?

Accepted Answer

After the initial exposure to an antigen, memory cells are produced by the immune system. These memory cells remain in the body and "remember" the antigen, so if the antigen is encountered again, the memory cells can quickly produce the appropriate antibodies to fight off the pathogen. This results in a faster and more efficient secondary immune response.

Question 15

B cells are activated by ________ and T cells are activated by ______.

Accepted Answer

B cells are activated by soluble, intact antigens, whereas T cells are activated by antigen fragments that are presented on the surfaces of other cells, such as those presented by Major Histocompatibility Complex (MHC) molecules.

Question 16

Genes encoding antibodies are generated by a process in which DNA segments are _______ combined.

Accepted Answer

The process of generating genes encoding antibodies is called V(D)J recombination and involves the random combination of variable (V), diversity (D), and joining (J) gene segments. This generates a diverse repertoire of antibody genes, allowing the immune system to recognize and respond to a wide range of pathogens.

Question 17

What cellular structure is found to be expanded in plasma cells,but not in their precursor cells?

Accepted Answer

The rough endoplasmic reticulum (RER) is a cellular structure involved in protein synthesis and modification. Plasma cells are specialized B cells that secrete large amounts of antibodies. To deal with this high secretory demand, they have an expanded RER compared to their precursor cells. The other structures listed (nuclei, mitochondria, chloroplasts, lysosomes) are not specifically expanded in plasma cells.

Question 18

What is found on the surface of T cells?

Accepted Answer

T cell receptors are found on the surface of T cells and allow for specific interaction with a particular antigen. B cell receptors are found on the surface of B cells and serve a similar function, but are not found on T cells. T cell and B cell antigens refer to proteins that are recognized by the immune system as foreign, and are not typically found on the surface of T cells or B cells. Platelet receptors are not relevant to T cell function.

Question 19

The modified,harmless version of the tetanus toxin that is used to immunize infants is called a(n)_______.

Accepted Answer

The modified, harmless version of the tetanus toxin that is used to immunize infants is called a toxoid. It is no longer toxic but still elicits an immune response to provide protection against future exposure to the actual tetanus toxin. Therefore, the correct choice is C) toxoid.

Question 20

Some of the activated B cells remain in lymphoid tissue and respond rapidly at a later date if the antigen reappears in the body.Such cells are called __________.

Accepted Answer

Memory B cells are responsible for a rapid response upon re-exposure to an antigen. They "remember" the antigen and are able to quickly produce a large quantity of specific antibodies to neutralize the antigen before it can cause harm. Activation B cells, plasma cells, secretion cells, and antibody-producing cells are all terms used to describe B cells at various stages of differentiation or function, but do not specifically refer to B cells with memory capabilities.

Quiz 17: The Immune Response