Biology Lesson: A Pox No Longer Upon Us

Abstract
The first part of the lesson will use historical documents to help students understand the development and use of vaccines. The historical documents allow for the students to work with qualitative observations; these documents contain several hypotheses that remain the working basis of immunization.

During the second part of this lesson students will examine primary and secondary immune responses as they relate to the production of antibodies. The students will be asked to note the difference between the two responses based on a graph which they will construct. Once the students have completed both the historical documents and graph, they will be asked to relate both sets of information to each other.

Objectives
Students will be able:

1. Articulate the relationship of the vaccine to primary and secondary immune responses of the body.
2. Explain how knowledge about vaccinations developed.

Teacher Background
The human body contains many B and T cells which together can respond to a multitude of antigens. Clonal selection theory explains the effectiveness in which the body can respond to an antigen. That is, there exists a variety of B cells within the human body which have a different kind of antigen receptor on their cell surfaces. It is the activation of one of these that creates the selection for cloning. These B cells can produce effector cells called plasma cells that will produce antibodies to fight this particular antigen. Plasma cells are short lived. These activated B cells will also produce memory cells, although at a much lower proportion, that can remain in the body for years. These memory cells can, when activated by the same specific antigen, divide quickly and produce more effectors.

Let us say that the body is exposed to a particular antigen for the first time. This antigen activates the lymphocytes to produce clones and in turn, these clones produce specific effectors and memory cells. The invader is thus destroyed and there are now memory cells of this specific invader. This is a primary immune response. The next time that the person is exposed to this particular antigen the response is much faster and will produce a higher level of antibodies. This secondary immune response is the direct result of memory cells produced during the primary immune response. It is because of these memory cells and their rapid response that we can immunize against diseases.

Vaccinations are simply the injection of small amounts of attenuated virus or bacteria or their protein into the body. This exposure to an antigen will cause the body to have a primary response that will not make them ill with the disease but will produce memory cells for that specific antigen. It is the production of memory cells that will protect the person against future illness since these B and T cells can quickly respond the invader and overwhelm it. During the late 1700s, an English physician named Edward Jenner observed that people, who had been ill with cowpox, would not become ill with smallpox, a related but much more harmful virus. He used cowpox to inoculate a small child in 1796. Later testing proved that the child was immune to both cowpox and smallpox. Although Jenner is given much credit for producing the first vaccine, there were others before him using the same principle to produce immunity. Lady Montague was documented to have brought some of the ideas from Turkey to England.

(Note: World Health Organization declared smallpox eradicated in 1977, while routine vaccination of the American public ended in 1972. Stocks of smallpox virus still remain in laboratories here in the United States. Also the U.S. government retains vaccines made from live vaccinia—not dead—for use in case of an outbreak.)

Related and Resource Websites
Center for Disease Control http://www.cdc.gov
Fordham University (Modern History Source Book) http://www.fordham.edu
World Health organization http://www.who.gov
University of California http://www.library.ucla.edu
Campbell, Neil A. 1996. Biology. 4th ed. Benjamin/Cummings Publishing Co., Inc., Menlo Park, Ca.
DiSpezio, Michael. 1997. The Science of HIV. Automated Graphic Systems, USA.

Activity
1. Provide students with a copy of the instruction sheet and direct them in pairs to read historical documents and respond to the questions found on the data collection sheet. Note that the left side of the data sheet corresponds to the letter from Lady Montague and the right side to that of the journal entries of Edward Jenner.

2. Once students have filled out the sheet share with them that Edward Jenner is typically given credit for developing vaccinations. Who else should be given credit? Lady Montague? What about the women in the market in Turkey? Can the basis for vaccinations be traced even further back?

3. Share with the students that when the human body is exposed to an antigen, the lymphocytes respond. One of these responses is to produce antibodies which will help eliminate the intruder. This first reaction to an invader is called the primary immune response and the cells that are producing the antibodies are short lived. However, a second set of cells are produced and they remember this particular antigen and can produce the antibody when needed. These memory cells will respond when the body is invaded for a second, third or even fourth time by the same invader. In fact these memory cells remain in the body for many years following the first invasion. This should be somewhat of a review from the earlier lessons on immunity.

4. The students should then, on a separate sheet of graph paper, graph the data of antibody production. They will assume that at time 0 the body was invaded by an unknown antigen. That person was then exposed for a second time to the same antigen on day 40.

5. Students should answer the questions below the graph. What do they note about the type of pathogen that a vaccine is used to combat?

Embedded Assessment

Using mathematical information and background information, students should be able to describe the relationship of the vaccine to primary and secondary immune responses of the body in the charts.

Using historical information, students should synthesize information and be able to describe how knowledge about vaccinations was developed in their responses in the chart.