Irving Weissman’s Montana way

Whether on his favorite fly fishing stream or in his medical research laboratory, this world-renowned scientist applies energy, desire and ambition to all he does

By MSU Alumni Foundation

August 22^nd, 2025

It is likely that as you read this, Dr. Irving Weissman ’61, a pioneer in cancer biology and major instigator of the use of bone marrow stem cells for transplants, is wader-deep in his favorite Big Sky trout stream. Even at age 85, he returns to Montana every summer, rod in hand, carefully and creatively controlling the looping of the line as it skims over dark waters until a fish — hidden until now — takes the fly in a beautiful and sinuous movement.

It is probably not surprising that fly fishing is the favorite leisure pastime of the Montana State University graduate who has spent more than 65 years at Stanford University. In many ways, the creativity and persistence required in fly fishing mirrors his approach to research that has led to discoveries that have laid the foundation for possible cures for cancer and other fatal diseases. And it helps that his favorite fishing hole takes him back to the Treasure State.

“Montana is not hierarchical,” said Weissman. “The only thing that limits you in Montana is energy, desire and what you do.”

And Weissman has certainly done a great deal.

Born in Great Falls, Weissman admits that even as a child he was not the best of students. He was curious, and interested in what he was interested in. When he was about 10, he encountered “The Microbe Hunters,” by Paul de Kruif, a book given to him by his teacher. He was mesmerized.

“I knew then that I wanted to do medicine and research,” Weissman said. “I didn’t want to go into business.”

The descendent of businessmen — his grandfather was an immigrant Russian fur and hide trader and his father a local hardware store owner and entrepreneur — Weissman had his first taste of the life of a scientist in 1956, when he was just 16. He talked his way into a job with Dr. Ernst Eichwald, then the chair of the transplantation committee of the National Academy of Scientists who serendipitously had become the pathologist at Great Falls Deaconess Hospital. Disillusioned with academia, Eichwald had agreed to come to Great Falls from the University of Utah if he could do his research into skin transplantation in his spare time and if a portion of the institution’s profits could be dedicated to research. In 1954, Eichwald established the Laboratory for Experimental Medicine in Great Falls, which later became the McLaughlin Research Institute. The facility was visited by any number of giants in the scientific field as they drove across Montana, which contributed to the depth of Weissman’s early scientific education. Eichwald paid young Weissman $25 a month to care for the rats and mice in the lab, and along the way he mentored the budding scientist in the process.

Weissman credits Eichwald with teaching him the fundamentals of scientific research as well as how to think. Eichwald allowed Weissman to conduct his own experiments, and by his senior year Weissman was co-publisher of a scientific paper about transplantation biology.

It was about that time that Weissman bumped into another young man at Buttrey’s Department Store in Great Falls who was wearing a Caltech jacket. Weissman introduced himself to Leroy Hood, a Caltech student who was brought up in Shelby but was visiting his father in Great Falls. The two became fast friends. Hood later went on to develop ground-breaking scientific instruments that made possible major scientific advances including the sequencing of DNA. Hood, who has served on the faculties at the California Institute of Technology and the University of Washington, remains one of Weissman’s closest friends.

Weissman started his college education at Dartmouth College but quickly soured on the eastern lifestyle.

“I love the science. I feel like I still have a lot more science in me, and a lot more that I want to do.”

“First of all, there were no women at the college at all at the time,” Weissman said. “It was also the first time in my life that I faced antisemitism. But the clincher was my zoology course. I knew more about the subject matter than the professor.”

Weissman transferred to Montana State College, which he called “spectacular.” He primarily took graduate level science courses as an undergraduate and studied under Palmer D. “Dave” Skaar, who had launched a genetics institute at MSC. Weissman said he asked Skaar, a world-class geneticist, why he was in Bozeman and Skaar told him, “I just love this life.”

Weissman graduated early from MSC and went straight to Stanford Medical School, drawn by a curriculum that would allow him the freedom he valued and time to continue his research.

“Stanford Medical School was non-hierarchical in the same way Montana was,” Weissman said.

During medical school, Weissman studied with scientists at both Stanford and Oxford and discovered that T cells were made in the thymus. That discovery, in part, convinced Weissman to forgo an internship and residency once he earned his medical degree, resulting in a complete dedication to medical research.

Over the next 20 years, Weissman identified where many cell types in the immune system were made and how they worked. His work evolved and included many scientific firsts. He was part of a team that identified antibodies that could be used to isolate blood-forming stem cells first in mice, and then in humans. He was the first to identify and isolate human blood-forming stem cells responsible for the immune system, research that laid the foundation for possible new treatments for cancer, blood diseases and organ rejection.

“Irv is one of the major instigators of the use of bone marrow stem cells for transplants, and he defined their lineage and much of their biology,” Hood said.

Hood also points out that Weissman, who as a child didn’t want to be a businessman, “has also been effective in creating companies that bring clinical therapies for cancer and immune diseases.”

As a high school student, Irving Weismann, right, got his start as a research scientist under the guidance of Dr. Ernst Eichwald, left.

In 2004, Weissman was named the founding director of the Stanford Institute for Stem Cell Biology and Regenerative Medicine. In the same year, he became the co-founder of the successful Proposition 71, a California ballot initiative that established a constitutional right in the state to conduct stem cell research. The proposition overturned the 2001 Bush policy banning stem cell research in the U.S. In 2008, President Barack Obama overturned the national ban. Proposition 71 also authorized California to issue $3 billion in bonds to fund stem cell research, which sustained and supported important medical research funding rather than allowing science to be affected by the foibles of private investors. Throughout all those years he remained active in the workings of the McLaughlin Institute in Great Falls.

By the time Weissman had stepped down as the director of the Institute for Stem Cell Biology and Regenerative Medicine in 2017, he was recognized internationally for his leadership in the support of outstanding scientists who have performed stem cell transplantation, gene editing and treatment of precancerous clonal stem cell diseases. One of those scientists was Dr. Renee Reijo Pera, former vice president of research at Montana State and now chair of the Weissman Hood Institute.

During his career Weissman has received the Robert Koch Prize, the Rosenstiel Award, the Max Delbruck Medal, the Charles Rodolphe Brupbacher Prize, the Albany Medical Center Prize, the Wallace H. Coulter Award for Lifetime Achievement in Hematology and the American Computer and Robotics Museum Stibitz-Wilson Award.

Last November, Reijo Pera announced that the McLaughlin Institute would be renamed the Weissman Hood Institute at Touro University (a national medical school opening a branch at the institute) in honor of Weissman and Hood.

“Each of them has individually changed the face of medical science for the better, and together they have generated innovations that are valued at greater than $75 billion while also focusing on improving our overall health and our health in the face of devastating diseases,” Reijo Pera said in making the announcement. “They have traveled the world over, been in the most elite circles, but they have never forgotten their roots.”

Even though he is now at an age when some are happy to decamp to their recliner, Weissman is daily at his research bench in Stanford, working on science that may have applications in curing metastatic breast cancer and macular eye disease.

“I love the science,” Weissman said. “I feel like I still have a lot more science in me, and a lot more that I want to do.”

Weissman does find time to retreat to the ranch in the Bitterroot that he bought in 1991 with Hood and David Baltimore, the past president of Caltech and a Nobel Prize winner for his work in virology. Weissman has proudly taught Baltimore to fly fish. The three scientists and their families spend time there recharging, eating good food and, of course, talking about science.

“Irv and I both attribute our determined optimism, our innovation and creativity and our ability to get a remarkable amount of science done over the last 60 years to the roots, freedoms of action and wonderful communities that we experienced in Montana,” Hood said of his life-long friend. “Irv is a world leader in the stem cell field, and I expect one of these days he will win a Nobel Prize.”