Flu virus infects its host by first wiping off the immune system's cells, which are best equipped to neutralize the virus, discovers scientists. Confronted with a harmful virus, the immune system works to generate cells capable of producing antibodies perfectly suited to bind and disarm the hostile invader.
These virus-specific B cells proliferate, secreting the antibodies that slow and eventually eradicate the virus.
A population of these cells retains the information needed to neutralize the virus and takes up residence in the lung to ward off secondary infection from re-exposure to the virus via inhalation.
On the surface of these so-called memory B cells are high-affinity virus-specific receptors that bind virus particles to reduce viral spread.
While such cells should serve at the body's first line of defense, it turns out that flu virus exploits the specificity of the cells' receptors, using them to gain entry, disrupt antibody production, and ultimately kill the cells.
By dispatching its enemies in this fashion, the virus is able to replicate efficiently before the immune system can mount a second wave of defense.