A Japanese research team led by immunologist Masahiro Yamamoto has developed a way to curb cancers by reducing certain T cells that restrain the immune system.

Professor Yamamoto, of Osaka University's Research Institute for Microbial Diseases, and other researchers developed in tests using mice a method to stimulate weakened immune activity by restraining the cells. Their findings were published in the U.S. journal Science on Friday.

"It may lead to a new immunotherapy that does not trigger autoimmune diseases, so we want to engage in drug discovery," Yamamoto said.

Humans can defeat cancer cells and harmful microbes that enter the body with their immune functions. But excessively strong immunity can trigger an autoimmune reaction, or an attack against one's own body tissues.

In the human body, immune cells that spur immunity and cells that put the brakes on immunity usually work in balance. However, cancer tissues include more of the latter type, making it easier for cancer to grow.

Yamamoto's team found that, inside cancer tissues in mice, a type of regulatory T cell known as Th1-Treg uses a substance called PF4 to increase in number. By administering a neutralizing antibody to inhibit PF4, the team found that Th1-Treg decreases and that cells driving immunity become more active, thereby curbing cancer growth.

It is known that cancer patients with high levels of PF4 have lower rates of survival.

"We've found a neutralizing antibody against PF4 for humans, and we want to conduct a clinical trial with the support of pharmaceutical companies," Yamamoto said.

Th1-Treg is not the only type of regulatory T cell. Removing all types causes autoimmune diseases, but removing just Th1-Treg is unlikely to cause problems, the team said.