Antibody Structure, Function and Genetics
“What a memorable day! The Pneumococcal reactants were most exciting—sugarplums were dancing in my head.”
- —Michael Potter, “The Early History of Plasma Cell Tumors in Mice, 1954–1976.”
Matching Immunoglobulins to their Antigens
Potter and Leon's Ouchterlony Plate (1967) National Library of Medicine
In their Building 8 laboratory, Potter and Elizabeth Mushinski began screening the immunoglobulins produced by plasma cell tumors against all types of antigens to match antibody to antigen. In 1968, they identified the MOPC315 immunoglobulin and its antigen, pneumococcal C polysaccharide, which is a component of the bacteria that causes pneumonia. Michael P. Cancro, Ph.D., University of Pennsylvania
What Makes Immunoglobulins Differ Genetically?
Potter worked with Rose Lieberman on the third question he had scrawled: What is the genetic basis of antibody diversity? They found three genetic “types” in each immunoglobulin. “Isotype” genes on the constant regions determine the class and sub-class of the immunoglobulin. “Allotypes” distinguish the constant region sequences that are unique to the mouse strain. And “idiotypes” in the variable region reflect genetic sequences associated with an immunoglobulin’s specificity; sometimes immunoglobulins bind to the same antigen, but their idiotype genes are different.
The illustration, on the right, shows the basic structure of immunoglobulins. Molecules in the heavy chains weigh more than those in the light chains. The amino acids in the constant regions do not change, while those in the variable region usually do change. Potter asked how this structure affects how immunoglobulins protect the body.