A healthy T cell, a family that includes CD4+ cells,...

A healthy T cell, a family that includes CD4+ cells, which a UC San Diego study found has unexpected power in fighting cancer.  Credit: TNS/NIAID

SAN DIEGO — Researchers at the University of California, San Diego say a relatively unexplored pathway the immune system uses to recognize cancer is far more important than previously recognized.

The finding could help scientists design new cancer immunotherapies and predict responses to them.

When this pathway doesn't recognize mutated genes, tumors that exploit the mutations are more common, the researchers found. The relationship is even stronger than that of a better-known pathway.

The research highlights the complexity of the immune system, which consists of many different types of cells that interact with each other and abnormal and invading cells in a web of relationships that are still far from understood.

Scientists led by Hannah Carter, assistant professor of medicine at UC San Diego School of Medicine, researched the pathway between a subtype of T cells and a molecule found on immune cells.

Results were published recently in the journal Cell. The study can be found at j.mp/cancermhc2.

T cells are a class of white blood cells that recognize and kill infectious microbes and abnormal cells, including cancer cells. The subtype examined in the study is called CD4-plus, or "helper" T cells. It works with a family of molecules presented on the surface of immune cells, called MHC 2.

A related family, known as MHC 1, has received most of the attention in cancer immune therapy. But the study suggests MHC 2 could be even more important.

Normally, the MHC molecules signify the cells bearing them are "self," and should be left alone. When they present "nonself" molecules called antigens, such as from bacteria, viruses or cancer, they prime the immune system to destroy cells with those antigens.

The two molecules play complementary roles. While MHC 1 is displayed on all cells, MHC 2 is displayed only on immune cells, and also can present more antigens.

The researchers found that when MHC 2 strongly binds to an antigen, that antigen is less likely to show up in a tumor. Any incipient cancers with this antigen are presumably destroyed early, before a detectable tumor forms.

This relationship is even more pronounced than a previous finding the researchers made with MHC 1. That study was also published in Cell.


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