Scientists are closer to understanding how your immune system fights disease

• Those few, triggering protein fragments are termed "immunodominant."
• Unfortunately, the immune system sometimes makes poor choices about which epitopes to pay attention to, and which to ignore.
• Understanding of how immunodominance is conferred would enable vaccine designers to shift the immune system spotlight to parts of pathogens that they cannot change in efforts to escape detection.
• For example, a vaccine could be designed to target a protein fragment central to a virus's ability to reproduce, or to invade its prey.
• As part of the immune response, T cells, one type of white blood cell, partner with dendritic cells to make careful decisions about which pieces of pathogens will trigger a full-scale immune attack.
• Upon encountering an invader, a dendritic cell will "swallow it," cut it up, and carry the pieces to the nearest lymph node.
• Once in the lymph node, major histocompatibility complex (Mhc) proteins inside the dendritic cell present immunodominant epitopes on the cell's surface for consideration by T cells gathered there.
• Once activated by high enough levels of target epitope for long enough periods of time, T cells become armed and capable of destroying the pathogen in question.
• Kinetic stability determines whether, in the face of competing reactions within the immune system, an epitope:Mhc complex can remain intact on the dendritic cell surface long enough to demand T cell attention.
• Sant's team found that immunodominant peptides were likely to stay bound to Mhc molecules for an average of 150 hours, where nondominant epitopes held on for less than 10 hours.
• "What's exciting is that kinetic stability is determined by how tightly an epitope fits into the Mhc protein, and we can control that fit with standard techniques," Sant said.
• If confirmed, this discovery will bring immundominance and a major portion of the immune system under our control for the first time."