Sir MacFarlane Burnet, 85, an Australian microbiologist and virologist who was cowinner of the 1960 Nobel Prize for Medicine for his pioneering work in immunology research, died of cancer Aug. 31 in Melbourne.

Dr. Burnet was the retired director of the Walter and Eliza Hall Institute of Medical Research at the Royal Melbourne Hospital and a research professor emeritus of experimental medicine at the University of Melbourne.

His fellow winner of the 1960 Nobel was Dr. Peter Brian Medawar, then a professor of zoology and comparative anatomy at University College, London. Upon announcing their award, the Swedish Academy cited the researchers for their independent work in the discovery of acquired immunological tolerance, a discovery that solved one of the major obstacles in transplanting tissue from one person to another.

Work that both men did in this field led to major advances in such areas as grafting skin to severely burned persons and in organ transplant operations. Their work went far to explain why one person's body "rejects" tissue and organs from another, because of the immunological pattern contained in body cells that differs in every individual.

Dr. Burnet, who had begun his research in the 1920s, also produced important work dealing with influenza, poliomyelitis and herpes. He was the 1952 recipient of the prestigious Lasker Award of the American Public Health Association. The citation accompanying the award said it was given to him "for fundamentally modifying our knowledge of virus disease and the inheritance characteristics of viruses."

Over the years, Dr. Burnet had observed that outbreaks of influenza circled the globe about every two years. Utilizing a method he developed for cultivating bacterial viruses in chicken embryos, he found that each new strain of the disease was a mutant of the previous virus. The "old" virus had disappeared because people had developed immunity to it. They had no immunity from the "new" virus, however.

His technique with live chicken embryos involved inoculating them with material taken from a patient's throat and observing the resulting growth of viruses in the embryo after an incubation period. The test not only helped determine the presence of viruses, but also helped identify the variety. This helped not only in research dealing with influenza, but in studies of poliomyelitis, as well. Much of his work on the genetic material of viruses underlies current theories about viruses as cancer-causing agents.

In addition to the Nobel andLasker prizes, he was awarded the Emil von Behring Prize, West Germany's highest scientific award, in 1954 for his research in viruses. He was knighted in 1951, received the Order of Merit in 1958, and was created a knight commander of the British Empire in 1969. His other awards included the Copley Medal and the Royal Medal of the Royal Society.

Dr. Burnet served as president of the Australian Academy of Science from 1965 to 1969, and was a fellow of the American College of Physicians, the Royal College of Physicians and the Swedish Royal Academy of Science. In addition to teaching in England and Australia, he had lectured at Harvard and Johns Hopkins universities. He also was a member of the World Health Organization's medical research advisory committee in Geneva from 1957 to 1960.

Since retiring from research and teaching in 1965, he had written 16 books. Two of them were autobiographical in nature; the others interpreted science, especially medicine, for the lay reader. He wrote that one of his books, "Endurance of Life," was "ambitious and controversial, with a strong bias toward stressing the importance of genetics in all behavioral as well as in the structural aspects of the human being."

Frank Macfarlane Burnet was born Sept. 3, 1899 in Traralgon, Victoria, Australia. He was a graduate of Geelong College in Victoria, where he studied biology and medicine, and received his medical doctorate from the University of Melbourne in 1923. After serving as resident pathologist at the Royal Melbourne Hospital, he held a fellowship at the Lister Institute of Preventive Medicine in London. He received a second doctorate, from the University of London, in 1927, for his research in bacteriophages and viruses.

Returning to Australia in 1928, he joined the Walter and Eliza Hall Institute and the staff of the Royal Melbourne Hospital. In 1944, he was named director of the institute and professor of experimental medicine at the University of Melbourne.

His wife of 44 years, the former Edith Linda Marston Druce, died in 1973. Survivors include his second wife, the former Hazel Foletta Jenkin, whom he married in 1976, and three children by his first marriage.