The immune system's B cells protect us from disease by producing antibodies, or "smart bullets," that specifically target invaders such as pathogens and viruses while leaving harmless molecules alone. But how do B cells determine whether a threat is real and whether to start producing these weapons?
An international team of life scientists shows in the May 16 issue of the journal Science how and why these cells respond only to true threats.
"It is critical for B cells to respond either fully or not at all. Anything in between causes disease," said the study's senior author, Alexander Hoffmann, a professor of microbiology, immunology and molecular genetics in the UCLA College of Letters and Science. "If B cells respond wimpily when there is a real pathogen, you have immune deficiency, and if they respond inappropriately to something that is not a true pathogen, then you have autoimmune disease."
The antibodies produced by B cells attack antigens molecules associated with pathogens, microbes and viruses. A sensor on the cell's surface is meant to recognize a specific antigen, and when the sensor encounters that antigen, it sends a signal that enables the body's army of B cells to respond rapidly. However, there may be similar molecules nearby that are harmless. The B cells should ignore their signals something they fail to do in autoimmune diseases.
So how do the B cells decide whether to start producing antibodies?
"These immune cells are somewhat hard of hearing, which is appropriate because the powerful and potentially destructive immune responses should jump into action only when danger calls, not when it whispers," said Hoffmann.
The B cells make their response only when a rather high threshold is reached, Hoffmann and his colleagues report. A small or moderate signal from a harmless molecule, for instance gets no response, which reduces the risk of false alarms.
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|Contact: Stuart Wolpert|
University of California - Los Angeles