Dr. Yokoyama was recognized for his important discoveries on the role of natural killer (NK) cells, an interesting immune cell population that has cytotoxic activity and may play a key role in regulating the immune response as well as tumor cell killing. Specifically, Dr. Yokoyama’s research identified the Ly49A receptor, which is responsible for inhibiting NK cells, components of the immune system. The 1992 discovery, the first identification of an NK cell receptor, ultimately helped reveal how NK cells defend the body against viruses and kill certain types of tumors.
Prior to Dr. Yokoyama’s findings, scientists believed NK cells were insignificant to immunity because, unlike T and B cells, they didn’t appear to discriminate between particular pathogens or tumors.
In 2005 Dr. Yokoyama made further progress in understanding how NK cells function and what processes influence their potency. He found that NK cells work efficiently throughout life only if they are “licensed.” During licensing, Ly49A or another NK cell inhibitory receptor must bind to certain molecules in order to allow the cell to change and function properly.
His work has led to a host of other NK cell observations. Dr. Yokoyama says researchers in other labs are providing convincing evidence that NK cells may be involved in autoimmune conditions such as juvenile rheumatoid arthritis.
“I was of, course, delighted to be selected by the Arthritis Foundation’s review panel,” says Dr. Yokoyama. “It’s ironic. We didn’t set off specifically to do arthritis research.”
