HUMAN BIOLOGY

Resistance to antibiotics has become

common in part due to the widespread

overuse of antibiotics in the livestock

industry. A 2013 analysis of more than

250 turkey meat products sold to

U.S. consumers revealed that nearly

90 percent of the meat was contaminated with bacteria, such

as Salmonella, that cause food-borne illness in people. The

worst contamination was in ground meat from turkeys that had

been routinely fed antibiotics, not because the birds were sick,

but to prevent possible infection. As a result, the researchers

concluded, such needlessly medicated animals became

breeding grounds for resistant bacteria.

Several antibiotics routinely added to the feed of commer-

cially grown poultry and other livestock are the same ones used

in human medicine. The more microbes that become resistant

to such drugs fed to healthy food animals, the more risk each

of us faces of developing a hard-to-treat—or untreatable—

infection. You will likely be hearing more about this topic. A

growing number of infectious disease specialists are lobbying

for new regulations that prohibit the use of antibiotics in feed

given to healthy animals.

your future

7. The most common antigens are.
   a. nucleotides c. steroids
   b. triglycerides d. proteins


8. The ability to develop a secondary immune response is
   based on.
   a. memory cells d. effector cytotoxic
   b. circulating antibodies T cells
   c. plasma cells e. mast cells


9. Tears are part of the body’s defensive arsenal. What
   defense category do they fall into, and why?


10. Match the immunity concepts:
    inflammation a. neutrophil
    antibody secretion b. plasma cell
    phagocyte c. nonspecific response
    immunological memory d. purposely causing
    vaccination memory cell
    allergy production
    e. basis of secondary
    immune response
    f. nonprotective
    immune response

CritiCaL thinkinG

1. New research suggests a link between some microbes
   that normally live in the body and seemingly unrelated
   major illnesses. The gum disease called periodontitis itself
   is not life-threatening, for instance, but it is a fairly good
   predictor for heart attacks. Bacteria that cause gum disease
   can trigger inflammation. Thinking back to your reading in
   Chapter 7, how do you suppose that this response also may
   be harmful to the heart?


2. Given what you now know about how foreign invaders
   trigger immune responses, explain why mutated forms
   of viruses, which have altered surface proteins, pose a
   monitoring problem for a person’s memory cells.


3. Researchers have been trying to develop a way to
   get the immune system to accept foreign tissue as
   “self.” Can you think of some clinical applications for
   such a development?


4. Elena developed chicken pox when she was in
   kindergarten. Later in life, when her children developed
   chicken pox, she stayed healthy even though she was
   exposed to countless virus particles each day. Explain why.


5. By the 1790s when English physician Edward Jenner
   (right) was treating patients, people all over the world had
   been trying to protect themselves against the scourge of
   smallpox for centuries. Jenner observed that people who
   caught cowpox, a similar but less virulent disease, never
   got smallpox, and this led him to wonder if something
   about cowpox was protective. To test his hypothesis,
   he injected a young boy with material from cowpox
   scabs. After the boy’s bout of cowpox was over, Jenner
   injected him with pus from a smallpox sore. The boy
   stayed healthy, and the episode led to the discovery of
   vaccination—a term that literally means “encowment.”
   What do you think would happen if a physician tried this
   experiment today?

176 Chapter 9

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