Frank Dixon; created way to trace cell reactions

Dr. Frank Dixon, working in his lab at the Scripps Institute in San Diego. (ap file)

LOS ANGELES - Dr. Frank Dixon, an immunologist who pioneered the use of radiolabeling in molecular biology, died Friday at his home in suburban La Jolla Shores. He was 87.

Dr. Dixon, who was among the first to explain how autoimmune diseases worked and who founded the Scripps Research Institute in San Diego, had been suffering from aortic stenosis and apparently died of heart failure in his sleep, said Scripps spokesman Keith McKeown.

"Frank was the model of the modern scientist, demonstrating equal creativity and talent both as an investigator in the laboratory and as the institute's first director," said Dr. Richard A. Lerner, who succeeded him as president of Scripps.

In the postwar years when Dr. Dixon began his research, biologists were limited in their ability to trace the course of cellular reactions, relying primarily on their eyes and the microscope. He began his career at Harvard University with Shields Warren, who would become a key player at the Atomic Energy Commission.

Because of Warren's connection to the atomic commission, Dr. Dixon was able to procure radioactive iodine. He developed techniques to tag proteins and other molecules with it, enabling him to trace their progress through the body of experimental animals and determine where they ended up and in what quantities.

His isotope tracer techniques are still widely used, and researchers now employ a broad variety of isotopes for tracing chemical and biological reactions.

The technique was particularly appropriate for studying a phenomenon known as serum sickness. In the era before antibiotics, one method of treating bacterial infections was to inject the patient with blood serum from animals exposed to the germ.

Antibodies in the serum would destroy the bacteria, but the serum often would produce side effects that included fever, an enlarged spleen, joint pain, and rashes. These symptoms are similar to those of several diseases, including rheumatoid arthritis, rheumatic fever, and lupus, and Dr. Dixon reasoned that studying serum sickness in animals could provide insight into the origin of such afflictions.

It was known that the antibodies in the animal serum could bind to specific proteins in the blood, called antigens, forming antigen-antibody complexes. But no one knew what role these complexes played in disease.

Dr. Dixon labeled the antigens with radio-iodine and was able to show that the antigen-antibody complexes concentrated at the sites of tissue damage in the body - particularly in the heart, blood vessels, joints, and kidneys - and were presumably the cause of the damage.

He determined precisely how this process worked, the quantities required, and the role of complement, another component of the immune system.

Subsequently, he and his students were able to show that in humans, misguided immunological responses to natural proteins and viruses were the cause of many unexplained illnesses.

In 1951 Dr. Dixon was named the nation's leading medical researcher under age 35 by the American Association for the Advancement of Science. In 1975, he received the Albert Lasker Medical Research Award, frequently a precursor of the Nobel Prize.

In 1961, Dr. Dixon was recruited to form a department of experimental pathology at the Scripps Clinic. By 1986, when Dr. Dixon formally retired as president of the institute, its funding from the National Institutes of Health was $39 million per year, surpassing the Mayo Clinic and allowing the institute to call itself the largest "independent, nonprofit biomedical research center" in the country.

A native of St. Paul, Minn., and Navy lieutenant during World War II, Dr. Dixon leaves his wife of 62 years, Marion (Edward); two sons, Frank Jr. of Santa Ana, Calif., and Michael of Minneapolis; a daughter, Janet Keller of Champaign, Ill.; and four grandchildren.