New research, being reported by the Howard Hughes Medical Institute, has shown the feasibility of using positron emission tomography (PET) in monitoring the immune system for clinical purposes:
Writing in the November 15, 2005, issue of Proceedings of the National Academy of Sciences (PNAS), a team of researchers led by HHMI investigator Owen N. Witte at UCLA’s Jonsson Comprehensive Cancer Center reports the results of experiments that enabled the group to tune in to the cellular battles waged by the immune system deep in the body. Using positron emission tomography or PET, Witte and his colleagues were able to observe key cells of the immune system as they responded to tumors in mice…
PET is already a widely used technology. In conventional clinical settings it produces images of the body by detecting radiation emitted from radioactive substances, such as fluorodeoxyglucose, injected into the body. In the work reported by Witte’s group, PET was used to follow immune cells whose DNA included “reporter genes,” genes engineered to help concentrate chemical tracers detectable by PET imaging.
The experiments conducted by Witte’s group utilized mice whose immune systems had been suppressed and then replaced using bone marrow from another mouse. The donor marrow included cells with genes engineered to be detectable by PET. By inducing cancer in the mice, Witte and his team were then able to observe specific immune cells at work as they reacted to the tumor.
“The fact that we can visualize the cellular immune response without invading the body is an important advantage,” Witte noted. “We can see immune reactions in the body that would otherwise not be easy to see. If you test blood, for example, it may not tell you what’s going on in the liver or the spleen. With this technique, the sensitivity for monitoring the immune system is incredible because you’re seeing the whole body.”
That global perspective makes it possible to see critical ancillary responses in addition to the specific cellular battles of the immune system at the site of a tumor, for example. In their experiments Witte’s group was able to see the lymph nodes, which resided at some distance from the tumor, spring into action. Lymph nodes are a critical part of the immune system, helping to recruit key disease-fighting immune cells.
More at the HHMI…