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Researchers at Stanford's School of Medicine have revealed in a new study how T cells, the immune system's foot soldiers respond to an enormous number of potential health threats. 

The study revealed significant similarities in the structure of binding sites, which allow a given T cell to recognize many different invaders that provoke an immune response. 

"Until now, it often has been a real mystery which antigens T cells are recognizing; there are whole classes of disease where we don't have this information," said Michael Birnbaum, a graduate student who led the research at the School of Medicine in the laboratory of K. Christopher Garcia, the study's senior author and a professor of molecular and cellular physiology and of structural biology, in the press release.

"Now it's far more feasible to take a T cell that is important in a disease or autoimmune disorder and figure out what antigens it will respond to," Birnbaum said.

T cells are triggered into action by protein fragments, called peptides, displayed on a cell's surface. In the case of an infected cell, peptide antigens from a pathogen can trigger a T cell to kill the infected cell. The research provides a sort of rulebook that can be used with high success to track down antigens likely to activate a given T cell, easing a bottleneck that has constrained such studies, the press release added.

The research involved exposing a handful of mouse and human T-cell receptors to hundreds of millions of peptides. Researchers then compiled and compared the detailed sequence - the order of the chemical building blocks - of the peptides that bound to each T-cell receptor.

"T-cell receptors are 'cross-reactive,' but in fairly limited ways. Like a multilingual person who can speak Spanish and French but can't understand Japanese, a receptor can engage with a broad set of peptides related to one another," Birnbaum said.

The research has been published in the journal Cell.