Class Activities

Mystery Solving: Immune Response

I. Mystery solving as an approach to problem-based learning

Everyone likes a good detective mystery. Here's how to bring it to your classroom. Begin the sequence by summarizing the immune response learning unit using a flow chart. In working through the chart, make sure the students understand the local and systemic consequences of failure in the flow.

How does this become a murder mystery? Have the students do analyses of lab reports of patients (actual names changed, of course). The instructor can divide students into cooperative learning groups. The challenge for the student groups in this cooperative learning environment is to pursue "five whys" (that isóask "why" until you have pursued the pathology to its ultimate cause). The students must act as detectives and proceed in a methodical and logical manner to identify the following:

1. The type of incident (cell death, malfunction, or sometimes nothing special at all--the latter to remind them to avoid confusing pathology with the merely unusual);

2. The "victim:" bronchioles, CD-4 helper T lymphocytes, appendix, etc.; determine whether a "crime" has occurred or not (murders are crimes, i.e., HIV infections; suicides are not, i.e. autoimmune disorders);

3. What the weapon and culprit were (specific pathogens, for example).

The intention is to get the students to relate pathologies to specific body functions, following the sequence of failure to its starting point. To be able to arrive at this reference point demonstrates not only a command of the topic but a facility for problem-solving. Since the class will have been looking into the leukocytes and the immune response, these examples will help the students to firm up their understanding of the roles of the white blood cells.

Here are some sample situations. In some of the cases, there is a "red-herring:" a false clue, as there are with most people. I provide a copy of each situation and then give them to each group:

A. George is 15 years old and presents with the following:

1. Severe lower right abdominal pain that has had a sudden onset with no foregoing associated trauma;

2. Body temperature 400 Celsius;

3. Differential WBC:

80% mature neutrophils

15% lymphocytes T cells normal

5% monocytes

<1% eosinophils

<1% basophils

Total leukocytes: 20,000/mm3

Diagnosis: (keep this to yourself until the student groups have had their say): George most likely has acute appendicitis. What follow-up would confirm this diagnosis?

B. Alice, 9 years old, in April presents with:

1. Severe upper and lower respiratory problems: coughing, sneezing, wheezing, congestion, and tightness in chest;

2. Temperature at 380 Celsius;

3. Differential:

50% mature neutrophils

30% lymphocytes T cells normal

5% monocytes

13% eosinophils

2% basophils

Total leukocytes: 6,000/mm3

Diagnosis: hay fever certainly. The wheezing and tightness in the chest indicates possible asthma. Ask the students for their treatment suggestions: antihistamine and if asthma is confirmed an epinephrine analog. This may be a way to get the students to think about the smooth muscles around the bronchioles.

C. Mary, 29, presents with:

1. Mild flu-like symptoms including fatigue, yeast-like material in mouth;

2. Pinkish brown spots, 0.5-1.0 cm in diameter on back and legs;

3. Differential:

75% neutrophils, few bands

10% lymphocytes: most CD-8, few CD-4

14% monocytes

1% eosinophils

<1% basophils

Total leukocytes: 3,000/mm3

Diagnosis: Most likely an HIV infection. The low CD-4 count is the obvious sign. The yeast and the Kaposi-like marks are also indicators. However, other conditions can mimic HIV so the students should call for follow-up: ELISA and then Western Blot to confirm.

D. Henry, 59, presents with:

1. Severe bone pain in legs and in back;

2. Upper-left abdomen tender and enlarged;

3. Temperature: 360 Celsius;

4. Anemic: low hematocrit

5. Differential:

60% granulocytic band cells

10% neutrophils

20% lymphocytes

10% monocytes

Total leukocytes: 50,000/mm3

Diagnosis: Henry most likely has acute granulocytic leukemia. Follow-up work would include a bone marrow study.

At the end of their work, randomly choose one of the unknowns and ask one of the groups to explain what they have concluded, continuing in this manner until all groups have spoken once and all the situations tackled.

Here's a website you or your students might find useful:

http://www.ihot.com/~ecrandal/lrnnet03.htm