Scientists uncover hidden step in how the immune system prepares to fight cancer

The findings challenge the long-standing view that CD8-positive T cells - a type of immune cells that finds and destroys cancer cells - can leave the thymus in an inactive state and acquire their cancer-fighting abilities only after encountering threats elsewhere in the body. Instead, the research suggests that the thymus may help prepare these immune cells for rapid responses before they enter circulation.

CD8-positive T cells are among the immune system's primary cancer-fighting cells. The researchers found that PD-1 - a protein that is the target of several widely used cancer immunotherapy drugs - acts as a brake during their development, helping prevent these cells from becoming exhausted too quickly.

PD-1 is already the target of several immune checkpoint inhibitor therapies used to treat a wide range of cancers, making the discovery particularly relevant to ongoing efforts to improve those treatments.

The findings may provide insight into why some immune responses against cancer are powerful but short-lived. Researchers say future therapies may need to strike a balance between boosting the immune system's attack on tumors and preserving the long-term function of cancer-fighting cells.

In preclinical models, removing PD-1 helped these immune cells control certain tumors more effectively. But the stronger response came at a cost: the cells became exhausted sooner, limiting their long-term cancer-fighting ability.

The findings come as researchers seek ways to make cancer immunotherapies more effective and longer lasting. While these treatments have transformed care for many patients, they do not work for everyone and can lose effectiveness over time.

The findings were based primarily on laboratory and preclinical model studies, and additional research will be needed to determine how they apply to patients.

Source:

Mayo Clinic

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