When a cell has to destroy any of its organelles or protein aggregates, it envelops them in a membrane, forming an autophagosome, and then moves them to another compartment, the lysosome, for digestion. Two years ago, Rockefeller University assistant professor Christian Mnz showed that this process, called autophagy, sensitizes cells for recognition by the immune system's helper T cells. But he didn't know how often this pathway is used or how efficient it is. Now, a new study published online today in the journal Immunity goes a long way toward addressing these questions and shows that the pathway is so common that it could be a valuable new way of boosting vaccine efficacy.
There are two types of T cells: Helper T cells encourage their counterpart, killer T cells, to hunt down and attack invading pathogens. T cells typically recognize antigens only once they're presented to them by major histocompatibility compex (MHC) scaffolding molecules on a cell's surface. Antigens on MHC class I molecules are recognized by killer T cells and had originally been thought to come only from sources inside a cell (proteins from the nucleus or other cellular part); those on MHC class II molecules are recognized by helper T cells and had been thought to come from sources outside the cell, such as fragments of dead, infected cells. But as Mnz discovered two years ago, an autophagy pathway allows intracellular antigens to be presented on MHC class II molecules.
Now Mnz, head of Rockefeller's Laboratory of Viral Immunobiology, and Dorothee Schmid, a graduate student in the lab, have shown that the autophagy pathway is far more widespread than they thought: They found that a surprising number of cells with MHC class II molecules on their surfaces used the autophagy pathway. In skin (epithelial) cells and two other types of immune cells (dendritic and B cells), 50 to 80 percent of the autophagosomes moved into the loading compartment for MHC class II molecules. "F
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Contact: Joseph Bonner
bonnerj@rockefeller.edu
212-327-8998
Rockefeller University
22-Dec-2006