A biochemist who received her Ph.D. from Yale University in 1923, Florence B. Seibert (1897-1991) is best known for her research in the biochemistry of tuberculosis. She developed the protein substance used for the tuberculosis skin test.
The protein substance used for the tuberculosis skin test was developed by Florence B. Seibert and was adopted as the standard in 1941 by the United States and a year later by the World Health Organization. In addition, in the early 1920s, Seibert discovered that the sudden fevers that sometimes occurred during intravenous injections were caused by bacteria in the distilled water that was used to make the protein solutions. She invented a distillation apparatus that prevented contamination. This research had great practical significance later when intravenous blood transfusions became widely used in surgery. Seibert authored or coauthored more than a hundred scientific papers. Her later research involved the study of bacteria associated with certain cancers. Her many honors include five honorary degrees, induction into the National Women's Hall of Fame in Seneca Falls, New York (1990), the Garvan Gold Medal of the American Chemical Society (1942), and the John Elliot Memorial Award of the American Association of Blood Banks (1962).
Florence Barbara Seibert was born on October 6, 1897, in Easton, Pennsylvania, the second of three children. She was the daughter of George Peter Seibert, a rug manufacturer and merchant, and Barbara (Memmert) Seibert. At the age of three she contracted polio. Despite her resultant handicaps, she completed high school, with the help of her highly supportive parents, and entered Goucher College in Baltimore, where she studied chemistry and zoology. She graduated in 1918, then worked under the direction of one of her chemistry teachers, Jessie E. Minor, at the Chemistry Laboratory of the Hammersley Paper Mill in Garfield, New Jersey. She and her professor, having responded to the call for women to fill positions vacated by men fighting in World War I, coauthored scientific papers on the chemistry of cellulose and wood pulps.
Although Seibert initially wanted to pursue a career in medicine, she was advised against it as it was "too rigorous" in view of her physical disabilities. She decided on biochemistry instead and began graduate studies at Yale University under Lafayette B. Mendel, one of the discoverers of Vitamin A. Her Ph.D. research involved an inquiry into the causes of "protein fevers"—fevers that developed in patients after they had been injected with protein solutions that contained distilled water. Seibert's assignment was to discover which proteins caused the fevers and why. What she discovered, however, was that the distilled water itself was contaminated—with bacteria. Consequently, Seibert invented a distilling apparatus that prevented the bacterial contamination.
Seibert earned her Ph.D. in 1923, then moved to Chicago to work as a post-graduate fellow under H. Gideon Wells at the University of Chicago. She continued her research on pyrogenic (fever causing) distilled water, and her work in this area acquired practical significance when intravenous blood transfusions became a standard part of many surgical procedures.
After her fellowship ended, she was employed part-time at the Otho S. A. Sprague Memorial Institute in Chicago, where Wells was the director. At the same time, she worked with Esmond R. Long, whom she had met through Wells's seminars at the University of Chicago. Supported by a grant from the National Tuberculosis Association, Long and Seibert would eventually spend thirty-one years collaborating on tuberculosis research. Another of Seibert's long-time associates was her younger sister, Mabel Seibert, who moved to Chicago to be with her in 1927. For the rest of their lives, with the exception of a year in Sweden, the sisters resided together, with Mabel providing assistance both in the research institutes (where she found employment as secretary and later research assistant) and at home. In 1932, when Long moved to the Henry Phipps Institute—a tuberculosis clinic and research facility associated with the University of Pennsylvania in Philadelphia—Seibert (and her sister) transferred as well. There, Seibert rose from assistant professor (1932-1937), to associate professor (1937-1955) to full professor of biochemistry (1955-1959). In 1959 she retired with emeritus status. Between 1937 and 1938 she was a Guggenheim fellow in the laboratory of Theodor Svedberg at the University of Upsala in Sweden. In 1926 Svedberg had received the Nobel prize for his protein research.
Seibert's tuberculosis research involved questions that had emerged from the late-nineteenth-century work of German bacteriologist Robert Koch. In 1882 Koch had discovered that the tubercle bacillus was the primary cause of tuberculosis. He also discovered that if the liquid on which the bacilli grew was injected under the skin, a small bite-like reaction would occur in people who had been infected with the disease. (Calling the liquid "old tuberculin," Kock produced it by cooking a culture and draining off the dead bacilli.) Although he had believed the active substance in the liquid was protein, it had not been proven.
Using precipitation and other methods of separation and testing, Seibert discovered that the active ingredient of the liquid was indeed protein. The next task was to isolate it, so that it could be used in pure form as a diagnostic tool for tuberculosis. Because proteins are highly complex organic molecules that are difficult to purify, this was a daunting task. Seibert finally succeeded by means of crystallization. The tiny amounts of crystal that she obtained, however, made them impractical for use in widespread skin tests. Thus, she changed the direction of her research and began working on larger amounts of active, but less pure protein. Her methods included precipitation through ultrafiltration (a method of filtering molecules). The result, after further purification procedures, was a dry powder called TPT (Tuberculin Protein Trichloracetic acid precipitated). This was the first substance that was able to be produced in sufficient quantities for widespread use as a tuberculosis skin test. For her work, Seibert received the 1938 Trudeau Medal from the National Tuberculosis Association.
At the Henry Phipps Institute in Philadelphia, Seibert continued her study of tuberculin protein molecules and their use in the diagnosis of tuberculosis. Seibert began working on the "old tuberculin" that had been created by Koch and used by doctors for skin testing. As Seibert described it in her autobiography Pebbles on the Hill of a Scientist, old tuberculin "was really like a soup made by cooking up the live tubercle bacilli and extracting the protein substance from their bodies while they were being killed." Further purification of the substance led to the creation of PPD (Purified Protein Derivative). Soon large quantities of this substance were being made for tuberculosis testing. Seibert continued to study ways of further purifying and understanding the nature of the protein. Her study in Sweden with Svedberg aided this research. There she learned new techniques for the separation and identification of proteins in solution.
Upon her return from Sweden, Seibert brought the new techniques with her. She began work on the creation of a large batch of PPD to serve as the basis for a standard dosage. The creation of such a standard was critical for measuring the degree of sensitivity of individuals to the skin test. Degree of sensitivity constituted significant diagnostic information if it was based upon individual reaction, rather than upon differences in the testing substance itself. A large amount of substance was necessary to develop a standard that ideally would be used world-wide, so that the tuberculosis test would be comparable wherever it was given. Developing new methods of purification as she proceeded, Seibert and her colleagues created 107 grams of material, known as PPD-S (the S signifying "standard"). A portion was used in 1941 as the government standard for purified tuberculins. Eventually it was used as the standard all over the world.
In 1958 the Phipps Institute was moved to a new building at the University of Pennsylvania. In her memoirs, Seibert wrote that she did not believe that the conditions necessary for her continued work would be available. Consequently, she and Mabel, her long-time assistant and companion, retired to St. Petersburg, Florida. Florence Seibert continued her research, however, using for a time a small laboratory in the nearby Mound Park Hospital and another in her own home. In her retirement years she devoted herself to the study of bacteria that were associated with certain types of cancers. Her declining health in her last two years was attributed to complications from childhood polio. She died in St. Petersburg on August 23, 1991.
In 1968 Seibert published her memoirs, which reveal her many friendships, especially among others engaged in scientific research. She particularly enjoyed international travel as well as driving her car, which was especially equipped to compensate for her handicaps. She loved music and played the violin (privately, she was careful to note).
Further Reading on Florence B. Seibert
New York Times, August 31, 1991.