Common molecule notifies immune system of prost...( it tries to destroy the cell carrying i...),Health

In 1982, while at the University of Texas at Austin, Allison discovered T cell antigen receptors, the fork-like proteins that recognize the molecular signals on invading cells. Each T cell has a different receptor as determined by genetics and a random process. There are trillions of different T cell receptors possible, a number greater than the number of cells in the human body.

In normal tissue, the distribution of receptors found on T cells is random. That is, a batch of T cells will have a range of receptors, with none being more common than the others.

But in the new work, one of Allison's colleagues, Peter Savage, discovered that the cancerous prostate glands of mice harbored many T cells carrying a specific receptor. That meant that a single T cell had recognized the malignancy and had replicated.

Savage found the overrepresented receptor in 15 of 20 mice with prostate cancer. That told us something was going on, said Allison. You don't see this in normal mice.

At this point, the team knew that the immune system of the mice was recognizing a particular signpost of malignancy. But they had no idea what the signpost was.

The obvious question was, What are these T cells seeing? said Allison. And that's when the hard work started.

The team chopped up tumor cells in a dish and mixed them with antigen presenting cells and T cells carrying the receptor they had identified. The T cells switched on, which showed we had really gotten the right receptor, said Allison. However, during control experiments, the team also found that nearly any type of tissue, if it was chopped up, would activate the T cells.

This started some head scratching, said Allison. Because if every tissue activated the T cells, it meant that the signpost was not specific to the cancer cells.

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