High School Student Exercise for Identification of Immunoglobulin Isotype Switching During An Infection

Developed by P. Fisher
© American Association of Immunologists 1996

Focus
High school chemistry students are presented an organic unit which culminates with a study of biochemistry. Building on exposure from titering and a basic ELISA in biology, the students studied the physical and chemical properties of antigens and antibodies, the different isotypes, the relationships between the two and the role each plays in the primary and secondary immune responses with emphasis on the response times of the different Ig isotypes. The ELISA performed in this unit tested the responses of three antibodies [IgA, IgG, and IgM] during a primary and a secondary infection in mice. The assay was performed over a five day period. The classes were divided into nine or ten groups with each group testing either one Ig in three test samples (total of nine groups) or the (-) and (+) controls. Minor adjustments were made in equipment used, basically a 50-drop/mL microtip transfer pipette for the Eppendorf or Titertex pipettes used in professional laboratories. The serum was diluted only for purposes of dispensing the required small volume (2uL) in the first wells for dilutions. The students had the opportunity to perform an ELISA very comparable to the professionals using the same reagents, equipment and volumes. The purposes of the different solutions and reagents utilized in the assay and the order of the procedures were thoroughly discussed to enhance the students' understanding of the results of the ELISA. The final results were determined quantitatively by spectrophotometric reading. From this data the students calculated the average and corrected titer for the nine sample dates and the response level of the three antibodies during the two infections in the same mice. They prepared a graph utilizing the class data. These results were then compared to theoretical and 'real life' conclusions. (Supported by AAI Summer Teacher's Fellowship Program)

Introduction
Rationale:
High school chemistry students are presented an organic chemistry unit which culminates with a study of biochemistry. This is an excellent opportunity to again implement an exercise to alert students of the important correlations between Biology, Chemistry, and Mathematics. During biology last year, my students had the opportunity to perform a titer and a basic ELISA. This unit will build on the previous ELISA with procedures to discern between IgM production early after exposure to an antigen and IgG production relatively later after exposure. The students will study the physical and chemical properties of antigens and antibodies, the different antibody isotypes, the relationships between the two and the role each plays in the primary and secondary immune responses with emphasis on the response times of the different Ig isotypes.

Goal:
Test the adaptive response of three antibody isotypes to a pathogen using mouse serum with E. intestinalis and study the chemistry involved in these responses.

Objectives:

1. Define immunity and explain the relationship between an antigen and an antibody.
2. Contrast the main characteristics of antigens and antibodies with emphasis on structure and chemical composition.
3. Understand the mechanics of the immune responses in primary and secondary infections in relation to IgA, IgG, and IgM antibodies.
4. Perform an ELISA to test responses of IgA, IgG, and IgM in a primary and secondary infection.
5. Graph data and interpret results as they relate to clinical implications.

To receive a copy of this curriculum, please contact: The American Association of Immunologists, telephone: (301) 634-7178, fax: (301) 634-7887, email infoaai@aai.org.