Answering each of the  questions in case.  

60 Journal of College Science Teaching


Resistance Is Futile . . . or Is It? The
Immunity System and HIV Infection
by Annie Prud’homme-Généreux

lthough the majority of
people are prone to HIV
infection, some individu-
als remain uninfected de-

spite repeated exposure. This case
study uses the results of the land-
mark paper by Paxton and his col-
leagues (1996) that offered the first
breakthrough in understanding why
some people are protected against
HIV infection. The case study uses
an interrupted progressive disclo-
sure format, during which students
make hypotheses, predict the out-
come of experiments, and compare
their predictions with real data. I
am aware of another case study
developed using Paxton’s paper
(“Rediscovering Biology,” 2011).
The aims, activities, and topics
covered by that case are different,
and I recommend that instructors
review the Rediscovering Biology
case, particularly the excellent mul-
timedia and introductory literature
that accompanies it. This case is
appropriate for first-year biology
students with knowledge of the im-
mune system (cellular and immoral
immunity) and HIV infection.

By the end of the case, students will
be able to

• formulate testable hypotheses and
design experiments to investigate

• predict the results of experiments
given competing hypotheses;

• interpret data and compare to pre-
dicted outcomes;

• describe cellular and humoral im-
munity, HIV structure, and HIV
infection; and

• debate the pros and cons of per-
sonal knowledge of HIV immu-

Classroom management
This case was developed for a
90-minute class but can be adapted
for a longer or shorter class period.
Students should be well versed in
humoral and cellular immunity and
the mechanism of HIV infection be-
fore attempting this case. For each
section of this case, teams of three
to four students are provided with
printed handouts of the case and are
directed to work with their group on
solving the questions. This is always
followed by a large class discussion
during which the inputs of each team
are shared. Use of a whiteboard on
which student volunteers show their
predictions during the class discus-
sion is very helpful.

Following this case, students can
be assigned research projects to
update their knowledge and under-
standing of this issue. Several lines
of investigation are suggested:

• The CCR5 mutation is common
among people of European de-
scent but not among other popula-
tions. Students explore and com-
pare the proposed hypotheses that
explain the evolution of this trait.

• Since Paxton’s paper was pub-
lished, mutations in human genes
other than CCR5, for example in
CCR2, have been shown to pro-
tect against HIV infection or slow
down the progression of the dis-
ease to AIDS. Review what some
of these genes do and how they
are thought to exert their protec-
tive effect (e.g., see O’Brien,
2003; O’Brien & Moore,

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