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 prevalenceof 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 makethis decision?

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?

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 __________.