PHILADELPHIA - A recently identified immune cell that directs other cells to fight infection plays a critical role in regulating the immune system in both health and disease. Researchers from the University of Pennsylvania School of Medicine have discovered how a stimulatory molecule and a protein found on the membrane of another immune cell make T helper 17 cells multi-taskers of sorts. Th17 cells protect the body against infection and cancer, but are also culprits in some autoimmune diseases and out-of-control, cancerous cell growth.

This new understanding that Th17 cells manage to play both sides of the fence suggests that targeting or inhibiting the involved protein pathways might be a new way to treat cancer, chronic infection, and some autoimmune diseases. Previous studies have linked excessive amounts of Th17 cells in the body to such autoimmune diseases as multiple sclerosis, psoriasis, rheumatoid arthritis, and Crohn's disease.

First author and postdoctoral fellow Chrystal Paulos PhD; senior author Carl June, MD, professor of Pathology and Laboratory Medicine, and colleagues have found that a protein called inducible costimulator (ICOS) is necessary for the growth and function of human Th17 cells, while CD28, a transmembrane protein on CD4 cells, stops the ICOS signal. What’s more, human Th17 stimulated with ICOS shrank human tumors implanted in a mouse model faster than those stimulated with CD28. The findings appear in this week’s Science Translational Medicine. June is also the Program Director of Translational Research for the Abramson Family Cancer Research Institute at Penn.

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