Q: Why does the immune
system react faster to a pathogen if it's been exposed to that pathogen
before? A: When the immune
system is exposed to the pathogen for
the first time, there aren't many cells which are already specifically
ready to fight it. Though it takes some time to replicate enough
of the appropriate T & B-cells
to fight the pathogen, some of the T and B
cells which are produced during the initial infection stay around
in the body just in case the pathogen comes again. Some of these
cells that stay are cells called memoryT
& B-cells. These special memory
cells are specially equipped to quickly respond to the pathogen
if it infects the body again.