Immune System

Tracking the Immune System

A new imaging probe illuminates the body's defense system as it fights cancer

The human immune system is complex, with multiple cell types stationed all over the body, ready to launch an attack at the first sign of infection. However, there has been no clinical tool to measure an immune response as it travels through the body. Such a tool would be helpful in monitoring immune reactions to diseases such as cancer. There have been cases in which the immune system successfully fights a tumor, and others in which it stimulates tumor growth. Finding an effective drug to treat cancer is also tricky, as many drugs actually suppress immune function, causing infections that could be life threatening. Understanding how the immune system reacts to certain cancers and drugs could help clinicians better diagnose and treat patients.

Now scientists at UCLA's Jonsson Comprehensive Cancer Center have developed an imaging probe for positron emission tomography (PET) that tracks an immune response throughout the body as it fights off cancer and infection. The scientists have published the results of their study in the online edition of the journal Nature Medicine.

The researchers' goal was not to track specific kinds of immune cells, but to image an immune response as a whole. To do that, they looked for a biological process characteristic of most types of immune cells and developed a probe to measure that process.

"If we wanted to measure a specific cell type, such as a T cell, we could have made a marker and attached a radionucleotide," says Owen Witte, a researcher at UCLA's Jonsson Comprehensive Cancer Center and the senior author of the study. "But we wanted a more global monitor of multiple cell types, and we came up with looking at a fundamental process called the DNA salvage pathway."

This pathway is essentially a DNA recycling mechanism that immune cells use to quickly and efficiently generate new cells. Most cells in the body can generate cells from scratch, slowly building new cells from glucose and sugars. However, in the presence of infection, immune cells have to act fast to make more cells for defense. These cells recycle floating bits of nucleotides--the building blocks of DNA--from food or dying cells, making more DNA that then churns out new immune cells.

 

 

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