1.   Another chemical test suggested that the heme was attached to a protein fragment.

2.   Each T cell has a slightly different shape so every size and shape of protein fragment can be recognized.

3.   Scientists have found that when a T cell recognizes a foreign protein fragment, that by itself is not enough to set off a strong immune response.

4.   T cells, on the other hand, spot protein fragments called peptides displayed like tiny molecular ID cards on the surface of all cells.

5.   The body can make billions of different T cells, the soldiers of the immune system, each able to recognize a particular protein fragment.

6.   The newly-exposed protein fragments, or antigens, are then spotted by the immune system, which treats them as foreign and begins making antibodies against them.

7.   The protein fragment stimulates the production of bone marrow cells which give rise to immune and blood cells.

8.   The scientists were inspired to begin their study after research by others indicated that it might be possible to turn off killer T cells with particular protein fragments.

9.   The two Harvard researchers first selected T cells that reacted with a particular protein fragment, or peptide, in myelin.

10.   Then the researchers found a second protein fragment, secreted by tumors, that also squelches metastases, Folkman said.