41. Immune System

Which of the following is a characteristic of adaptive immunity?

Why is HIV a dangerous pathogen?

Why does our immune system not usually attack our own healthy tissues?

New flu shots are needed every year to protect against infection because of __________.

Besides helper T cells, what are two other types of cells that HIV infects?

When searching for a donor for an organ transplant, doctors try to match the __________ of the donor and recipient as closely as possible.

The idea behind vaccination is to induce __________ without requiring the vaccinated individual to get sick.

A vaccine may contain __________.

A type of cell that makes immunizations effective is the __________.

How do antibodies to foreign blood groups come to exist in the body?

What do the antibodies secreted by plasma cells (the effector cells of humoral immunity) do to attack their targets?

What is the role of dendritic cells in the primary immune response?

Which of the following cell types carries out humoral immunity?

Which of the following functions of plasma-cell-secreted antibodies promotes phagocytosis of foreign bacteria?

The proliferation of the B lymphocyte to which a specific antigen binds is referred to as __________.

Once you have been exposed to an antigen, you develop immunity against the same antigen because __________.

The antigen-binding sites of an antibody molecule are formed from the molecule's variable regions. Why are these regions described as variable?

The body produces antibodies complementary to foreign antigens. The process by which the body comes up with the correct antibodies to a specific invader is most like __________.

A viral infection in a cell results in __________.

What is the primary difference between the innate and adaptive immune responses? a. The innate immune response does not distinguish between pathogens, while the adaptive immune response does. b. Only the innate immune response is activated by antigens. c. The adaptive immune response generates immunological memory and is more specific than the innate immune response. d. The innate immune response does not kill cells; the adaptive immune response does.

An epitope associates with which part of an antigen receptor or antibody? a. the tail b. the heavy-chain constant regions only c. variable regions of a heavy chain and light chain combined d. the light-chain constant regions only

Which statement best describes the difference between responses of effector B cells (plasma cells) and those of cytotoxic T cells? a. B cells confer active immunity; cytotoxic T cells confer passive immunity. b. B cells respond the first time a pathogen is present; cytotoxic T cells respond subsequent times. c. B cells secrete antibodies against a pathogen; cytotoxic T cells kill pathogen-infected host cells. d. B cells carry out the cell-mediated response; cytotoxic T cells carry out the humoral response.

What is the difference between an epitope and an antigen?

Which of the following statements is true? (A) An antibody has one antigen-binding site. (B) A lymphocyte has receptors for a single antigen. (C) Every antigen has a single epitope. (D) A liver or muscle cell makes two classes of MHC molecule

Which of the following statements is not true? a. An antibody has more than one antigen-binding site. b. A lymphocyte has receptors for multiple different antigens. c. An antigen can have different epitopes. d. A liver or muscle cell makes one class of MHC molecule.

Which of the following best describes the difference in the way B cells and cytotoxic T cells deal with invaders? a. B cells confer active immunity; T cells confer passive immunity. b. B cells send out antibodies to attack; certain T cells can do the attacking themselves. c. T cells handle the primary immune response; B cells handle the secondary response. d. B cells are responsible for the cell-mediated immune response; T cells are responsible for the humoral immune response.

What is one of the differences between CD4+ and CD8+ T cells? a. CD4+ cells are immature, and CD8+ cells are mature. b. CD4+ cells are activated, and CD8+ cells are not. c. CD4+ cells interact with class II MHC proteins, and CD8+ cells interact with class I MHC proteins. d. CD4+ cells activate cell-mediated responses, and CD8+ cells activate humoral responses.

Which of the following should be the same in identical twins? a. the set of antibodies produced b. the set of MHC molecules produced c. the set of T cell antigen receptors produced d. the set of immune cells eliminated as self-reactive

Cytotoxic T cells are able to recognize infected body cells because a. the infected cells display foreign antigens. b. the infected cells produce antigens. c. infected cells release antibodies into the blood. d. helper T cells destroy them first.

Explain how gene recombination leads to the production of vast numbers of different B-cell receptors.

Describe how HIV is transmitted and how immune system cells in an infected person are affected by HIV. What are the most effective means of preventing HIV transmission? Why is AIDS particularly deadly compared with other viral diseases?

What steps are required for most B cells to become fully activated and differentiate into plasma cells?

Why is clonal selection necessary for the adaptive immune response but not the innate immune response? Select True or False for each statement. T/F The adaptive immune response uses receptors to recognize pathogens, and the innate immune response does not. T/F There is more receptor diversity in the adaptive immune response than in the innate immune response. T/F Cells in the innate immune response do not require activation, and those in the adaptive immune response do. T/F Clonal selection is used for targeting pathogens, and the innate immune response is used only to stop blood flow from the wound.

Helper T cells recognize the self-nonself complex on ___________ cells, while cytotoxic T cells recognize the complex on ___________ cells.

What would a vaccine have to contain to protect a patient from chicken pox? Explain why we don't have vaccines for HIV.

In the condition myasthenia gravis, antibodies bind to and block certain receptors on muscle cells, preventing muscle contraction. This condition is best classified as an a. immunodeficiency disorder. b. exaggerated immune reaction. c. allergic reaction. d. autoimmune disorder.

Which of the following outcomes would be expected if somatic hypermutation did not occur? a. The diversity of pattern-recognition receptors would be significantly lowered. b. B and T lymphocytes would not be able to produce receptors that recognize antigens. c. The adaptive immune response would not be activated by pathogens. d. The secondary immune response to a repeat infection would produce the same antibodies as those made in the primary immune response.

Which of the following statements is not true? a. An antibody has more than one antigen-binding site. b. An antigen can have different epitopes. c. A lymphocyte has receptors for multiple and different antigens. d. A bacterium has more than one antigen.

Propose a hypothesis to explain how self-reactive B cells are identified and eliminated during maturation.

Propose an explanation for why we need a flu shot year after year, instead of only once early in life.

In developed countries, an enormous change has occurred within the human body over the past century—the loss of parasitic worms. Due to improvements in sanitation, roundworms that have inhabited human intestines (such as the hookworm above) and challenged our immune system for millions of years are no longer a threat. Does the end of this long-term relationship come at a cost? What is the hygiene hypothesis? What correlation does it attempt to explain?

SCIENTIFIC THINKING Pertussis (whooping cough) is caused by a bacterial infection, and symptoms include an intense cough that lasts for weeks, sometimes leading to pneumonia and death. A complete vaccination against pertussis requires five doses, completed by age 5. A pertussis outbreak occurred in California in 2010, and a news article reported the following: 'Among fully immunized kids, there were about 36 cases for every 10,000 children two to seven years old, compared to 245 out of every 10,000 kids aged eight to twelve.' Propose an explanation for these data and a public health solution based on your explanation.

In developed countries, an enormous change has occurred within the human body over the past century—the loss of parasitic worms. Due to improvements in sanitation, roundworms that have inhabited human intestines (such as the hookworm above) and challenged our immune system for millions of years are no longer a threat. Does the end of this long-term relationship come at a cost? Explain how the adaptive and innate immune responses work together to defend the human body against infection by parasitic worms.

Your roommate is rushed to the hospital after suffering a severe allergic reaction to a bee sting. After she is treated and released, she asks you (the local biology expert!) to explain what happened. She says, 'I don't understand how this could have happened. I've been stung by bees before and didn't have a reaction.' Suggest an explanation for what has happened to cause her severe allergic reaction and why she did not have the reaction after previous bee stings.

In developed countries, an enormous change has occurred within the human body over the past century—the loss of parasitic worms. Due to improvements in sanitation, roundworms that have inhabited human intestines (such as the hookworm above) and challenged our immune system for millions of years are no longer a threat. Does the end of this long-term relationship come at a cost? Pattern-recognition receptors have been identified that recognize worm products. Explain how these receptors are used to activate the adaptive immune response most appropriate for worm infection.

Compare the outcomes of two different cases of infectious diseases in a community. Case 1: A man with an infectious disease enters a community where the disease has not previously occurred. Case 2: A man with an infectious disease enters a community where almost everyone has been vaccinated against the disease.

In developed countries, an enormous change has occurred within the human body over the past century—the loss of parasitic worms. Due to improvements in sanitation, roundworms that have inhabited human intestines (such as the hookworm above) and challenged our immune system for millions of years are no longer a threat. Does the end of this long-term relationship come at a cost? Parasitic worms modulate their host's immune response by inducing the proliferation of regulatory T cells. What role do these cells play in the adaptive immune response? How could this effect on regulatory T cells be linked to the hygiene hypothesis?

Organ donation saves many lives each year. Even though some transplanted organs are derived from living donors, the majority come from patients who die but still have healthy organs that can be of value to a transplant recipient. Potential organ donors can fill out an organ donation card to specify their wishes. If the donor is in critical condition and dying, the donor's family is usually consulted to discuss the donation process. Generally, the next of kin must approve before donation can occur, regardless of whether the patient has completed an organ donation card. In some cases, a family member overrides the donor's wishes. Do you think that family members should be able to overrule the stated intentions of the potential donor? Why or why not? Have you signed up to be an organ donor? Why or why not?

In developed countries, an enormous change has occurred within the human body over the past century—the loss of parasitic worms. Due to improvements in sanitation, roundworms that have inhabited human intestines (such as the hookworm above) and challenged our immune system for millions of years are no longer a threat. Does the end of this long-term relationship come at a cost? The roundworm Heligmosomoides polygyrus is a natural intestinal parasite of mice, and it offers an excellent model of the immunology of worm infections in humans. Scientists evaluated the impact of parasitic roundworms on immune disorders using mice prone to developing type 1 diabetes mellitus. Five-week-old mice were infected with H. polygyrus (Hp). Two weeks later, half of the mice were cured of the infection (Rx). When the mice were 40 weeks old, scientists calculated the percentage of mice that developed diabetes in both groups: those exposed to roundworms and those in uninfected control groups (** means P<0.01). What two conclusions are supported by the results shown below?

One of the key difficulties in the development of anti-HIV drugs is the fact that HIV only infects humans. This precludes the testing of drugs in animals and instead requires that drugs be tested on volunteer human subjects. The developing world (particularly sub-Saharan Africa and Southeast Asia) has the highest rates of HIV infection. Consequently, drug companies frequently conduct studies in these regions. Some people decry such tests, fearing that drug companies may profit hugely from the use of economically disadvantaged people. Others counter that such tests are the only way to find new and cheaper drugs that will ultimately help everyone. What do you think are the ethical issues surrounding trials of anti-HIV drugs in the developing world? Which side do you think has the more morally compelling argument?

In developed countries, an enormous change has occurred within the human body over the past century—the loss of parasitic worms. Due to improvements in sanitation, roundworms that have inhabited human intestines (such as the hookworm above) and challenged our immune system for millions of years are no longer a threat. Does the end of this long-term relationship come at a cost? There is a strong association between the prevalence of diabetes mellitus in parents and their children. If you were a physician, would you ask parents who have type 1 diabetes to intentionally infect their children with intestinal worms? What additional information would you need to make this decision?