Leroy E. Hood

Leroy E. Hood, born in 1938, American molecular biologist who has been instrumental in the development of molecular biotechnology—the manipulation of biologically significant molecules to create products that benefit human beings. Hood's many contributions include a device that facilitates the large-scale analysis of deoxyribonucleic acid (DNA), the genetic material of all organisms. He has also contributed significantly to the understanding of autoimmune diseases—illnesses in which the immune system mistakenly attacks the body’s own healthy tissues.

Born in Missoula, Montana, Hood received a bachelor’s degree from the California Institute of Technology (Caltech) in 1960 and a master’s degree from Johns Hopkins University in 1964. He then returned to Caltech, where he received a doctoral degree in 1968. Hood was appointed professor of biology at Caltech in 1970; seven years later he was named the Ethel Wilson and Robert Bowles Professor of Biology. Hood left Caltech in 1992 to join the faculty of the University of Washington, where he is the William Gates III Professor of Biomedical Sciences and founder of the department of molecular biotechnology.

Among Hood’s achievements is the first automated DNA sequencer, a device that enables scientists to determine the order, or sequence, of chemicals within DNA called nucleotide bases. The task of identifying this order is extremely challenging because human DNA contains more than 3 billion base pairs. The machine uses four fluorescent dyes, each of which is specific for a single nucleotide base. It incorporates a laser, which stimulates chemicals in the dyes; a detector, which identifies the emissions of the stimulated chemicals; and a computer, which interprets data from the detector. The machine determines the order of the nucleotide bases within fragments of DNA that have been separated from human cells. The automated DNA sequencer made possible the Human Genome Project, a 13-year collaboration of scientists from around the world that completed a map of all the genes in the human body in 2003.

Another of Hood’s achievements is determining how the human body produces the multitude of antibodies—that is, protein molecules that defend the body against potentially harmful substances. Hood showed that the genes responsible for producing antibodies are constantly rearranged as cells grow. This process of rearrangement, called gene shuffling, makes it possible for human cells to produce hundreds of millions of different types of antibodies from a relatively small number of genes.

Hood continues to investigate the immune system and medical disorders involving the immune system. In 1989 he used engineered antibodies to combat a condition in mice that resembles human autoimmune disease. In 1996 he identified the sequence of nucleotide bases within the DNA segment that specifies the makeup of T-cell receptors, components of the immune system involved in fighting infection. Scientists are investigating T-cell receptors to help design vaccines against such diseases as acquired immunodeficiency syndrome (AIDS) and other infectious diseases.

For his work on antibody diversity, Hood was awarded the prestigious Albert Lasker Basic Medical Research Award in 1987, which he shared with Japanese molecular biologist Susumu Tonegawa and American molecular geneticist Philip Leder. Hood is also the recipient of 1984 3M Life Sciences Award and the 1987 Louis Pasteur Award for Medical Innovation.